PUBLISHING HOUSE TSTU

Ministry of Education of the Russian Federation

M. I. Lebedeva, B. I. Isaeva, I. V. Yakunina

PRACTICUM ON ANALYTICAL CHEMISTRY

Approved by the University Academic Council

Publishing house TSTU

REVIEWERS:

Candidate of Chemical Sciences, Associate Professor of the Department of Inorganic and physical chemistry TSU named after G. R. Derzhavina,

A. I. Ryaguzov

Candidate of Chemical Sciences, Associate Professor TSTU

O. A. Korchagina

L33 Lebedeva M. I., Isaeva B. I., Yakunina I. V. Workshop on analytical chemistry / Under the general editorship. M. I. Lebedeva. Tambov: Tamb publishing house. state tech. Univ., 2002. 80 p.

ISBN 5-8265-0167-7

The workshop contains a theoretical introduction to methods of qualitative and quantitative analysis, facilitating the assimilation of the material, detailed description methods for performing laboratory work. There are review questions at the end of each lab.

Designed for students of non-chemical specialties.

ISBN 5-8265-0167-7	Lebedeva M. I., Isaeva B. I.,
	Yakunina I. V., 2002
	Tambov State
	Technical University (TSTU), 2002

EDUCATIONAL EDITION

LEBEDEVA Maria Ivanovna, ISAEVA Bella Ivanovna, YAKUNINA Irina Vladimirovna

PRACTICUM ON ANALYTICAL CHEMISTRY

Editor T. M. Glinkina

Computer prototyping engineer M. N. Ryzhkova

LR No. 020851 dated 09.27.99 LR No. 020079 dated 04.28.97

Signed for publication on March 11, 2002.

Times New Roman typeface. Format 60 × 84 / 16.

Offset paper. Offset printing. Volume: 4.65 conventional units. oven l.; 4.5 academic publications l. Circulation 200 copies. P. 155

Publishing and Printing Center of Tambov State Technical University

392000, Tambov, Sovetskaya, 106, building 14

INTRODUCTION

The basis of environmental monitoring is a combination of various chemical sciences, each of which requires the results of chemical analysis, since chemical pollution is the main factor in the adverse anthropogenic impact on nature. The goal of analytical chemistry is to determine the concentration of pollutants in various natural objects. They are natural and waste waters of various compositions, bottom sediments, precipitation, air, soils, and biological objects.

Analytical chemistry is the science of methods for identifying chemical compounds, the principles and methods of determining chemical composition substances and their structures. She happens to be scientific basis chemical analysis.

Chemical analysis is the experimental acquisition of data on the composition and properties of objects.

This concept was first scientifically substantiated by R. Boyle in the book “The Skeptical Chemist” (1661) and introduced the term “analysis”.

Analytical chemistry is based on the knowledge gained from studying courses: inorganic, organic, physical chemistry, physics and mathematics.

The goal of studying analytical chemistry is to master modern methods analysis of substances and their application to solve national economic problems. Careful and constant monitoring of production and facilities environment based on the achievements of analytical chemistry. V. Ostwald wrote: “Analytical chemistry, or the art of recognizing substances or their constituent parts, occupies a special place among the applications of scientific chemistry, since the questions that it makes it possible to answer always arise when trying to reproduce chemical processes for scientific or technical purposes. Thanks to this significance, analytical chemistry has long been met with constant concern for itself...”

This textbook is compiled in relation to the standards and training programs in analytical chemistry and physical and chemical methods of analysis of specialties of Tambov State Technical University.

For a long time, analytical chemistry was dominated by the so-called “classical” methods of analysis. Analysis was seen as an “art” and depended sharply on the “hands” of the experimenter. Technological progress required faster, simple methods analysis. Currently, most mass chemical analyzes are performed using semi-automatic and automatic instruments. At the same time, the price of the equipment is compensated by its high efficiency.

Currently, it is necessary to use powerful, informative and sensitive analytical methods to control concentrations below the MPC. Indeed, what does the normative “absence of a component” mean? Perhaps its concentration is so low that it cannot be determined using the traditional method, but it still needs to be done. Really, environmental protection− challenge of analytical chemistry. It is fundamentally important that the limit of detection of pollutants by analytical methods is not lower than 0.5 MAC.

1 ANALYTICAL CHEMISTRY AS A SCIENCE

1.1 Chemical analysis

At all stages of any production, technical control, i.e. work is carried out to control product quality during technological process in order to prevent defects and produce products that comply with technical specifications and state standards.

Technical analysis is divided into general - analysis of substances found at all enterprises (analysis of H 2 O, fuel, lubricants) and special - analysis of substances found only at

given enterprise (raw materials, intermediate products, production waste, final product).

To this end, every day thousands of analytical chemists perform millions of analyzes in accordance with the relevant international GOST.

Analysis procedure - a detailed description of the performance of analytical reactions, indicating the conditions for their implementation . Its task is to master experimental skills and the essence of analytical reactions.

Analytical chemistry methods are based on various principles.

1.1.1 Classification of analysis methods

1 By objects of analysis− inorganic and organic.

2 By purpose - qualitative and quantitative.

The founder of qualitative analysis is considered English scientist Robert Boyle who first described detection methods SO 2 4 − and Cl − ions with the help of Ba 2 + and Ag + ions, and also applied

organic dyes as indicators (litmus).

However, analytical chemistry began to develop into a science after the discovery by M. V. Lomonosov of the law of conservation of the weight of substances at chemical reactions and the use of balances in chemical practice.

Thus, M.V. Lomonosov is the founder of quantitative analysis.

Quantitative Analysis allows you to establish quantitative relationships components of a given compound or mixture of substances. In contrast to qualitative analysis, quantitative analysis makes it possible to determine the content of individual components of the analyte or the total content of the analyte in the object under study.

Methods of qualitative and quantitative analysis that make it possible to determine the content of individual elements in the analyzed substance are called elemental analysis; functional groups – functional analysis ; individual chemical compounds characterized by a certain molecular weight, − molecular analysis.

A set of various chemical, physical and physicochemical methods for separating and determining individual structural (phase) components of heterogeneous systems that differ in properties and physical structure and limited from each other by interfaces are called

phase analysis.

3 By method of execution− chemical, physical and physicochemical methods.

4 By sample mass - macro - (0.1 ... 1.0 g); semi-micro − (0.01 ... 0.10 g); micro − (0.001 ... 0.010 g);

ultramicroanalysis − (< 0,001 г).

1.1.2 Methods for performing an analytical reaction

Analytical methods are based on obtaining and measuring analytical signal, those. any manifestation of chemical and physical properties substances as a result of a chemical reaction.

Analytical reactions can be carried out by "dry" or "wet" methods. Thus, flame coloring reactions (Na + − yellow; Sr 2 + − red; Ba 2 + − green), the formation of colored “pearls” of borax are carried out “dry” way.

2B 4O 7
		– “pearls” of various colors.
	Ni2+

Most often, analytical reactions are carried out in solutions. The analyzed object (an individual substance or a mixture of substances) can be in any state of aggregation (solid, liquid, gaseous). The object to be analyzed is called a sample or sample. The same element in a sample can be in different chemical forms. For example: S 0, S 2 −, SO 2 4 −, SO 3 2 −, etc. Depending

depending on the purpose and purpose of the analysis, after transferring the sample into solution, elemental analysis(determination of total sulfur content) or phase analysis (determination of sulfur content in each phase or in its individual chemical forms).

When performing a particular analytical reaction, it is necessary to strictly observe certain conditions for its occurrence (temperature, pH of the solution, concentration) so that it proceeds quickly and has a sufficiently low detection limit.

1.1.3 Signals of qualitative analysis methods

1 Formation or dissolution of precipitate

Hg2 + + 2J− →↓ HgJ2 ;	HgJ2 + 2KJ− → K2 [HgJ4].

2 Appearance, change, disappearance of the color of the solution (color reactions)

Mn2 + → MnO− 4 →↓ MnO2 4 − .

used color purple green

3 Gas release

SO3 2 − + 2H+ → SO2 + H2 O .

4 Reactions of formation of crystals of a strictly defined shape (microcrystalloscopic reactions)

Type of crystals

5 Flame color reactions.

1.1.4. Classification of analytical reactions

All analytical reactions can be classified according to the purpose or range of objects for which these reactions are used.

1 Group reactions, when the same reagent reacts with a group of ions, giving the same signal. So, to separate a group of ions (Ag +, Pb 2 +, Hg 2 2 +), they react with Cl − ions, and white precipitates are formed, AgCl, PbCl 2, Hg 2 Cl 2.

2 Selective (selective) reactions. Example: starch iodine reaction. For these purposes, organic reagents are used. Example: dimethylglyoxime + Ni 2 + → formation of a scarlet-red precipitate of nickel dimethylglyoximate.

By changing the conditions of the analytical reaction, non-selective reactions can be made selective. Example: if the reactions Ag + , Pb 2 + , Hg 2 2 + + Cl - are carried out when heated, then PbCl 2 does not

precipitates because it is highly soluble in hot water.

3 Complexation reactions, used for the purpose of masking interfering ions. Example: To detect Co 2 + in the presence of Fe 3 + using KSCN, the reaction is carried out in the presence of F − ions. In this case, Fe 3 + + 4F − → [FeF 4 ] − , KH = 10-16, while KH [ Fe (SCN) 4 ] − ≈ 10 − 5, therefore Fe 3 + ions are complexed and do not interfere with the determination of Co 2 + -ions.

1.1.5 Reactions used in analytical chemistry

1 Hydrolysis (by cation, by anion, by cation and anion)

Al3 + + HOH ↔ Al(OH) 2 + + H+ ;

CO3 2 − + HOH ↔ HCO3 − + OH− ;

Fe3 + + (NH4) 2 S + HOH → Fe (OH) 3 + ….

2 Oxidation-reduction reactions

MnSO4 + K2 S2 O8 + H2 O Ag + → HMnO4 + KHSO4 + H2 SO4.

3 Complexation reactions

CuSO4 + 4NH4 OH → [ Cu (NH3 ) 4 ] SO4 + 4H2 O .

4 Precipitation reactions Ba 2 + + SO 2 4 − →↓ BaSO 4 .

1.1.6 Analytical classification of cations and anions

Table 1.1

Analytical

Group reagent

Acid-base

K+, Na+, NH4+

Ba2+ , Sr2+ , Ca2+

H2SO4

MeSO4 ↓

Al3+, Cr3+, Zn2+,

NaOH ex.

MeOn −

Sn (II, IV), As (III, V)

NH4 OH ex.

Me(OH)m ↓

Continuation of the table. 1.1

Mg2+ , Mn2+ , Fe2+ ,

Fe3+, Bi3+, Sb (III,V),

NaOH ex.

Me(OH)m ↓

(Zn2+)

NH4 OH ex.

Cu2+, Cd2+, Co2+,

Me(OH)m ↓

Ni2+, Hg2+

NaOH ex.

Ag+, Pb2+, Hg2 2+

Men Clm ↓

Hydrogen sulfide

K+ , Na+ , NH4 + , Mg2+

(NH4 )2 CO3 + NH4 OH +

NH4Cl,

MeCO3 ↓

pH~ 9

Zn2+ , Al3+ , Cr3+

(NH4 )2 S + NH4 OH +

Me(OH)m ↓

NH4Cl, pH~ 9

Fe3+		MeS ↓
Fe3+		MeS ↓
Cu2+ , Cd2+ , Br3+ , Sn
(II, IV) Hg2+ , As (III,	H2S → HCl,	MeS ↓
	pH ~ 0.5
Ag+ , Pb2+ , Hg2 2+		MnClm ↓

Classification of anions

Group reagent – BaCl2.

Group I - soluble barium salts: Cl-, Br-, I-, NO3 -, S2-, CH3 COO-, SCN-, 4-, 3-, BrO3 -, CN-, ClO3 -, ClO4 -.

Group II - sparingly soluble barium salts: F-, CO3 2-, SO4 2-, SO3 2-, S2 O3 2-, SiO3 2-, CrO4 2-, PO4 3-.

1.1.7 Analysis scheme for identifying an unknown substance

1 Dry matter coloring

black: FeS, PbS, Ag2 S, HgS, NiS, CoS, CuO, MnO2, etc.;

orange: Cr2 O7 2-, etc.;

yellow: CrO4 2-, HgO, CdS; red: Fe(SCN)3, Co2+;

blue: Cu2+.

2 Flame color.

3 Test for water of crystallization.

4 The action of acids on dry salt (gas?).

5 Selection of solvent (if room temperature, when heated) H 2 O, CH3 COOH, HCl, H2 SO4

, "Aqua regia", fusion with Na 2 CO3 and subsequent leaching.

It should be remembered that almost all nitrates, all potassium, sodium and ammonium salts are soluble in water!

6 Monitoring the pH of the solution (only for water-soluble objects).

7 Preliminary tests (Fe 2+ , Fe3+ , NH4 + ).

8 Detection of a group of cations and anions.

9 Cation detection.

10 Anion detection.

Laboratory work № 1

REACTIONS FOR DETECTION OF CATIONS AND ANIONS IN SOLUTION

Purpose of the work: qualitative reactions for the detection of various ions for the purpose of their subsequent identification from a mixture.

Instruments and reagents: a stand with test tubes, a glass rod with a soldered platinum wire, an alcohol lamp, potassium, sodium, strontium, barium salts and others.

Experiment 1. Detection of K+ ions

a) To a neutral or acetic acid solution of potassium salt, add an equal volume of sodium hexanitrocobaltate solution and rub it with a glass rod on the walls of the test tube. In this case, a yellow crystalline precipitate of the double salt of sodium-potassium hexa-nitrocobaltate falls out:

2KCl + Na3 → ↓ K2 Na + 2NaCl;

2K+ + Na+ + -3 → ↓ K2 Na.

It is advisable to carry out the reaction at pH = 3, which corresponds to dilute solutions of acetic acid; in no case should the pH be more than 7.

b) Heat a glass rod with a platinum wire soldered into it, dip it in a solution of potassium chloride or put a little solid salt on it. Place the wire along with a drop of solution or particles of potassium salt into the colorless flame of an alcohol lamp. The flame will turn a characteristic purple color.

Experience 2. Detection of Na+ ions

a) Add an equal volume of solution K to a neutral solution of sodium salt and rub the glass rod against the walls of the test tube. A white crystalline precipitate will form:

NaCl + K → ↓ Na + KCl;

Na+ + - → ↓ Na .

The reaction should be carried out in a strictly neutral environment.

b) Volatile sodium compounds color the flame a characteristic yellow color (see experiment 1b). Experience 3. Detection of Ca2+ ions

Pour a solution of calcium salt into a test tube and add acetic acid until the reaction is acidic (2 - 3 cm3). Check the reaction of the medium using methyl red. Add ammonium oxalate solution drop by drop. In this case, a white crystalline precipitate of calcium oxalate gradually precipitates from the concentrated solution immediately, and from the diluted solution:

CaCl2 + (NH4 )2 C2 O4 → ↓ CaC2 O4 + 2NH4 Cl;

Ca2+ + C2 O4 2- → ↓ CaC2 O4 .

Magnesium, barium, and strontium ions interfere with the detection of calcium ions by this reaction, since they also form poorly soluble precipitates of the corresponding oxalates.

Experience 4. Detection of Sr2+ ions

a) Pour 2–5 cm3 of strontium salt solution into a test tube and add dropwise the same amount of ammonium sulfate or sulfuric acid solution. This will result in a white precipitate of strontium sulfate:

SrCl2 + (NH4 )2 SO4 → ↓ SrSO4 + 2 NH4 Cl;

Sr2+ + SO4 2- → ↓ SrSO4 .

Gypsum water can be used as a reagent. This reaction should be carried out by heating with a saturated solution of the precipitant.

b) Volatile strontium salts color the flame carmine-red (experiment 1b). Experience 5. Detection of Ba2+ ions

	a) Add 2–3 cm3 of a solution of potassium chromate or dichromate to a test tube with a solution of barium salt.
Heat the test tube in a water bath. In this case, a yellow crystalline precipitate forms:
	BaCl2 + K2 CrO4 → ↓ BaCrO4 + 2KCl;
	Ba2+ + CrO4 2- → ↓ BaCrO4 ,
	2BaCl2 + K2 Cr2 O7 + H2 O → ↓ 2BaCrO4 + 2KCl + 2HCl;

2Ba2+ + Cr2 O7 2- + H2 O → ↓ 2BaCrO4 + 2H+ .

The reaction should be carried out in a slightly acidic environment at pH = 3 ... 5. When precipitation in an acidic environment with a solution of potassium dichromate, it is recommended to add sodium acetate. The cations Ag+, Pb2+, Co2+, Bl3+, Cd2+ should be absent, since they interfere with the determination.

b) Barium salts color the flame yellow-green (see experiment 1b). Experience 6. Detection of Cu2+ ions

a) Add an excess of dilute ammonia solution to a test tube with a solution of copper (II) sulfate. This produces a soluble complex compound of blue-violet color.

CuSO4 5H2 O + 4NH3 = SO4 H2 O + 4H2 O.

b) Pour 1 - 2 cm3 of a solution of copper (II) salt into a test tube and add a few drops of a solution of hydrogen sulfide water, ammonium sulfide or sodium. This produces a black precipitate of copper sulfide.

CuSO4 + H2 S = = = ↓ CuS + H2 SO4 ;

Analytical chemistry

LABORATORY PRACTICUM

Minsk BSTU 2012

Educational institution

"BELARUSIAN STATE

UNIVERSITY OF TECHNOLOGY"

Analytical chemistry

educational and methodological association of higher educational institutions of the Republic of Belarus on chemical and technological education as an educational and methodological aid in the disciplines“Analytical Chemistry” and “Analytical Chemistry and Physico-Chemical Methods of Analysis”for students of chemical and technological specialties

UDC 543(076.5)(075.8)

A. E. Sokolovsky,N. F. Shakuro,A. K. Bolvako,E. V. Radion

Reviewers:

Department of Analytical Chemistry, Belarusian State University;

Doctor of Chemical Sciences, Head of the Laboratory of Chemical Catalysis of the Institute of Physical-Organic Chemistry of the National Academy of Sciences of Belarus N. G. Kozlov

All rights to this publication are reserved. Reproduction of the entire book or part thereof cannot be carried out without the permission of the educational institution “Belarusian State Technological University”.

ISBN 978-985-530-144-9.

The educational manual contains 20 laboratory works on qualitative and quantitative chemical analysis. Work on gravimetry and various titrimetry methods is multi-level - from standard to more complex, involving the analysis of multicomponent mixtures, real natural and technological objects. The peculiarities of the workshop are the varied topics of experimental tasks and computer processing of analysis results.

Basic information is provided about the chemical glassware and chemical analytical equipment used, methods of working with them, as well as the technique for performing chemical analytical operations.

The manual is intended for students of chemical engineering specialties.

UDC 543(076.5)(075.8)

BBK 24.4ya73

PREFACE

Organization of laboratory classes

Laboratory classes in analytical chemistry are conducted according to the schedule of the laboratory workshop (Table 1).

Table 1

Schedule of laboratory practical work in analytical chemistry


Topics "Introduction", " Theoretical basis analytical chemistry", "Qualitative analysis"
Safety briefing Techniques for performing operations in qualitative analysis Completing 2–4 LR on the topic “Qualitative Analysis” Defense of theoretical and practical material on the topics “Introduction”, “Theoretical foundations of analytical chemistry”, “Qualitative analysis”	Solving problems on the topic “Theoretical foundations of analytical chemistry” Computer testing on the topic “Theoretical foundations of analytical chemistry”
Subject "Gravimetric method of analysis»
Techniques for performing operations in gravimetry. Equipment for gravimetric analysis. Weighing equipment and weighing technology Perform 1–2 LR on the topic “Gravimetric method of analysis”	Defense of theoretical and practical material on the topic “Gravimetric method of analysis” and the section “Equilibrium in the sediment-solution system” Solving problems on the topic “Gravimetric method of analysis” and the section “Equilibrium in the sediment-solution system”
Computer testing on the topic “Gravimetric method of analysis” and the section “Equilibrium in the sediment-solution system”Themes "», Titrimetric method of analysis»
"Acid-base titration method Carrying out LR for calibration of measuring glassware Carrying out 1-2 tasks for the preparation and standardization of working solutions of the acid-base titration method Performing 2–4 control tests on the topic “Method of acid-base titration” Protection of theoretical and practical	Solving problems on the topic “Titrimetric method of analysis” Computer testing on the topic “Titrimetric method of analysis” Solving problems on the topic “Method of acid-base titration” and the section “Acid-base equilibrium” Computer testing on the topic “Method of acid-base titration” and the section “Acid-base titration”
End of table.
	1
Independent work under the supervision of a teacher	material on the topics “Titrimetric method of analysis”, “Method of acid-base titration” and the section “Acid-base balance” basic equilibrium"
Calculation (computer calculation) of the acid-base titration curve
Topics: “Methods of redox titration”, “Complexometry” Execution of 1–3 LR on standardization of working solutions of redox and complexometric titration methods Performing 3–5 control analyzes on the topics “Methods of redox titration” and “Complexometry”	Defense of theoretical and practical material on the topics “Methods of redox titration”, “Complexometry” and sections “Redox equilibrium”, “Complex formation” Solving problems on the topic “Methods of redox titration” and the section “Redox equilibrium” Computer testing on the topic “Methods of redox titration” and the section “Redox balance” Solving problems on the topic “Complexometry”
Computer testing on the topic “Complexometry”
Test problem task. Test	Protection of a problematic task. Test

Performing a problematic task

Students are allowed to perform laboratory work if:

underwent safety training;

passed the permit to perform laboratory work;

compiled reports and protected the work performed (have no more than two unprotected works);

defended theoretical and practical material on all previous topics. Laboratory work on quality chemical analysis is considered successfully completed if the student correctly identified all components of the sample. Laboratory work on chemical analysis is considered successfully completed if the result obtained by the student corresponds to the true value with an acceptable error. If an erroneous result is obtained, the student performs the work again, taking a control sample again.

After completing each cycle of work, a test of mastery of theoretical and practical material is carried out in the form of an individual oral interview with a teacher, a written answer followed by a defense, or computer testing. Students who have completed all laboratory and computational tasks on it are allowed to defend the topic.

Students who have fully completed the laboratory practical program are allowed to take credit for the course, which is conducted orally or in writing. When assigning a credit, all the student’s work during the semester is taken into account: performing laboratory work and calculation tasks, knowledge of theoretical and practical material, keeping a work journal.

Keeping a work log

Reports on laboratory work performed are prepared in a separate notebook, which is work log student. At the student's request, it is possible to conduct electronic work log with printed reports for checking by the teacher. After defending the work, the reports are signed by the teacher and serve as a document confirming the successful completion of the laboratory workshop.

Qualitative analysis» the report is submitted in Form 1 (see appendix).

When performing laboratory work on the topic “ Quantitative Analysis» the report is presented in different forms (see appendix) depending on the method of analysis being studied and the purpose of the work. When performing work on gravimetry the report is submitted in Form 2, when performing work on titrimetry– according to form 3 ( standardization of working solution) or form 4 ( performing benchmark analysis).

When performing quantitative analysis work, it is mandatory compliance with the rules for recording measurement results and indicating units of measurement. Measurement accuracy the main quantities and rules for recording measurement results are given in table. 2, a calculation accuracy values - in table. 3.

When performing all laboratory work on quantitative analysis, you can use the document Microsoft Excel“Workshop on AH and FHMA” with the aim of:

measurement uncertainty estimates;

carrying out Q-test to exclude gross errors, if there is a sufficient sample - 4 or more results of parallel measurements;

carrying out statistical processing of analysis results: calculation of average, variance, standard deviation, confidence interval, etc.

The workshop consists of three parts. The first part contains general information about safety precautions and rules of work in a chemical laboratory, basic techniques for working with chemical glassware and reagents, carrying out basic chemical analytical operations and analytical metrology. The second part is a description of 50 laboratory works on chemical methods of analysis. The third part is devoted to physicochemical methods of analysis. The basics and techniques for performing 75 works using domestically produced devices are outlined. For university students studying in areas of training for certified chemical and technological specialists. Can be used by students of energy, agricultural, medical, metallurgical, pedagogical and other universities, as well as employees of factory and environmental laboratories.

On our website you can download the book "Analytical Chemistry. Laboratory Workshop" Vladimir Germanovich Vasiliev for free and without registration in fb2, rtf, epub, pdf, txt format, read the book online or buy the book in the online store.

Name: Fundamentals of analytical chemistry. Practical guide
Zolotov Yu.A.
The year of publishing: 2001
Size: 9.29 MB
Format: djvu
Language: Russian

"Fundamentals of Analytical Chemistry. A Practical Guide" edited by Zolotov Yu.A., is a supplementary guide to two books on analytical chemistry by this author. The book contains a minor theoretical part. The possibilities of analysis and its methods are described. The manual contains practical work on the subject course. For pharmacy students.

Name: Pharmaceutical analysis
Bezugliy P.O.
The year of publishing: 2001
Size: 2.82 MB
Format: pdf
Language: Ukrainian
Description: The textbook “Pharmaceutical Analysis”, edited by P.O. Bezugloy, examines methods of pharmaceutical analysis of medications different ways using physicochemical and chemical methods. P... Download the book for free

Name: Analytical chemistry in diagrams and tables
Bolotov V.V., Zhukova T.V., Mikitenko E.E.
The year of publishing: 2002
Size: 1.21 MB
Format: pdf
Language: Russian
Description: The reference guide “Analytical chemistry in diagrams and tables”, edited by V.V. Bolotov, et al., examines practical issues of quantitative and qualitative analysis. Materials about the get... Download the book for free

Name: Lecture notes on analytical chemistry (quantitative analysis)

The year of publishing: 2002
Size: 1.47 MB
Format: pdf
Language: Russian
Description: The practical guide “Lecture notes on analytical chemistry (quantitative analysis)”, edited by V.V. Bolotova, examines in the form of lecture material the basics of quantitative analysis of the chemicals used... Download the book for free

Name: Lecture notes on analytical chemistry (qualitative analysis)
Bolotov V.V., Dynnik E.V., Zhukova T.V.
The year of publishing: 2002
Size: 1.56 MB
Format: pdf
Language: Russian
Description: The practical guide “Lecture notes on analytical chemistry (qualitative analysis)”, edited by V.V. Bolotova, examines in the form of lecture material the basics of qualitative analysis of the chemical used... Download the book for free

Name: Analytical chemistry. Problems and approaches. Volume 2
Kellner R., Merme J.
The year of publishing: 2004
Size: 8.45 MB
Format: djvu
Language: Russian
Description: Practical guide "Analytical chemistry. Problems and approaches" edited by Kellner R., et al., examines current issues of analytics in chemistry and pharmacy. The book consists of two volumes. The second... Download the book for free

Name: Analytical chemistry. Problems and approaches. Volume 1
Kellner R., Merme J.
The year of publishing: 2004
Size: 11.62 MB
Format: djvu
Language: Russian
Description: Practical guide "Analytical chemistry. Problems and approaches" edited by Kellner R., et al., examines current issues of analytics in chemistry and pharmacy. The book consists of two volumes. The first soda... Download the book for free

Name: Analytical chemistry. Workshop

The year of publishing: 2009
Size: 11.45 MB
Format: pdf
Language: Russian
Description: The textbook "Analytical Chemistry. Workshop" edited by Yu.Ya. Kharitonov, et al., examines data on the characteristics and types of qualitative analysis of various chemical elements (anions, cat... Download the book for free

Name: Examples and problems in analytical chemistry
Kharitonov Yu.Ya., Grigorieva V.Yu.
The year of publishing: 2008
Size: 145.97 MB
Format: pdf
Language: Russian
Description: The textbook “Examples and problems in analytical chemistry”, edited by Kharitonov Yu.Ya., et al., examines thematic problems on the topics of the analytical chemistry course. There are problems with solutions...

Ministry of Higher and Secondary Special Education of the Republic of Uzbekistan.

Tashkent Institute of Chemical Technology

Department of Analytical Chemistry

Laboratory works

in analytical chemistry

Chemical methods of analysis

TASHKENT-2004

This methodological instruction covers laboratory work of qualitative and quantitative chemical analysis. The qualitative analysis contains reactions of groups I-II and III of cations, reactions of anions, analysis of their mixtures, as well as methods for analyzing dry salt.

The quantitative analysis provides methods for performing titrimetric analysis based on neutralization, oxidation-reduction, complexation reactions and methods for calculating analysis results.

Methodical instructions provided for full-time and distance learning technological universities.

Approved by the methodological council of Tashkent Chemical Institute (protocol No.).

Compiled by: Assoc. Zakirov B.B.

prof. Nazirova R.A.

st.pr. Mukhamedova M.A.

Ass. Zhuraev V.N.

Reviewer: prof. Rakhmonberdiev A.

Qualitative analysis

Laboratory work No. 1

I groups

Group I includes the cations NH 4 +, K +, Na +, Mg 2+, etc.

Many of their salts are highly soluble in water, especially their sulfates, chlorides, and carbonates, which is of no small importance for analysis. Unlike other groups, group I cations do not have a group reagent.

Goal of the work : Studying the characteristic qualitative reactions of group I cations.

Cation reactions N.H. 4 +

1. Discovery with Nessler’s reagent – K 2 · 4 KOH.

To perform the reaction, take 1-2 drops of ammonium salt solution into a test tube and add 2-4 drops of Nessler’s reagent. A red-brown precipitate indicates the presence of the NH 4 + cation.

NH 4 Cl+2K 2 4KOH→ J↓+7KJ+KCl+2H 2 O

2. Reactions with alkalis:

NH 4 Cl+NaOH → NH 4 OH+NaCl

Add 3-4 drops of alkali to 2-3 drops of ammonium salt solution and heat in a water bath. By the smell of ammonia or by the blueness of litmus paper moistened with water and applied to the neck of the test tube, we determine the presence of ammonium cations.

Reactions of K cations +

1. Discovery by the action of sodium cobaltinite

2KCl+Na 3 [CO(NO 2) 6 ]→K 2 Na[CO(NO 2) 6 ] ↓+2NaCl

In this reaction, pour 1-2 drops of potassium salt solution into a test tube and add 3-4 drops of Na 3 [CO(NO 2) 6]. The formation of a yellow precipitate indicates the presence of K + cations.

2. Action by tartaric acid or sodium tartrate.

H 2 C 4 H 4 O 6 + CH 3 COONa → NaHC 4 H 4 O 4 + CH 3 COOH

KCl+NaHC 4 H 4 O 6 →KHC 4 H 4 O 6 ↓+NaCl

Pour 2-3 drops of potassium salt solution into the test tube, add 3-4 drops of tartaric acid and 3-4 drops of CH 3 COONa. Cool the test tube with the mixture under running water tap water and rub the walls of the test tube with the solution with a glass rod. A white crystalline precipitate forms. A precipitate does not form immediately because supersaturated solutions are formed and glass particles formed by rubbing with a glass rod are the center of crystallization and contribute to the formation of a precipitate.

Cation reactions Mg 2+

1. Opening with sodium hydrogen phosphate.

MgCl 2 +Na 2 HPO 4 +NH 4 OH MgNH 4 PO 4 ↓ +2NaCl+H 2 O

In this reaction, pour 2-3 drops of magnesium salt solution into a test tube, add 1-2 drops of ammonium buffer mixture and 3-4 drops of Na 2 HPO 4. A white crystalline precipitate forms.

2. Action of alkalis.

MgCl 2 +2NaOH→Mg(OH) 2 +2NaCl

MgCl 2 +2KOH→Mg(OH) 2 +2KCl

Pour 2-3 drops of magnesium salt solution, 2-3 drops of water and 3-4 drops of alkali into the test tube. A white amorphous precipitate forms.

Laboratory work No. 2

general characteristics cations II groups

Group II of cations includes Ca 2+, Ba 2+, Sr 2+ and others. Sulfates, phosphates, oxalates and carbonates of group II cations are poorly soluble in water. The group reagent of group II cations is (NH 4) 2 CO 3, which in the presence of an ammonium buffer mixture (pH = 9.2) precipitates them in the form of carbonates CaCO 3, BaCO 3 and SrCO 3.

The purpose of the work is to familiarize yourself with the general and characteristic reactions of group II cations.

Cation reactions Ba 2+

1. Potassium bichromate K 2 Cr 2 O 7 precipitates barium cations in the form of a yellow precipitate:

2BaCl 2 +2CH 3 COONa+K 2 Cr 2 O 7 +H 2 O→2BaCrO 4 + 2NaCl + 2CH 3 COOH + KCl

2-3 drops of BaCl 2 are poured into the test tube, 2-3 drops of CH 3 COONa and 3-4 drops of K 2 Cr 2 O 7 are added. As a result, a yellow precipitate is formed. The discovery of barium by this reaction is not interfered with by the Ca 2+ and Sr 2+ cations.

2. Discovery by ammonium carbonate.

BaCl 2 + (NH 4) 2 CO 3 →BaCO 3 ↓+ 2NH 4 Cl

2-3 drops of BaCl 2 are poured into the test tube and 3-4 drops of (NH 4) 2 CO 3 are added. A white crystalline precipitate forms.

Reactions of Ca +2 cations

1. Opening with ammonium oxalate (NH 4) 2 C 2 O 4:

CaCl 2 +(NH 4) 2 C 2 O 4 →CaC 2 O 4 ↓+2NH 4 Cl

Add 3-4 drops of (NH 4) 2 C 2 O 4 to 2-3 drops of CaCl 2 . A white crystalline precipitate forms.

2. Action of ammonium carbonate.

CaCl 2 +(NH 4) 2 CO 3 →CaCO 3 ↓ +2NH 4 Cl

To 2-3 drops of CaCl 2 add 3-4 drops of (NH 4) 2 CO 3. A white precipitate forms.

Laboratory work No. 3

Systematic mixture analysis I And II groups of cations.

1. Discovery of cations N.H. 4 + .

To do this, pour 1-2 drops of the control mixture into the test tube, add 3-4 drops of Nessler's reagent. A red-brown precipitate indicates the presence of NH 4 + cations.

2. Separation I And II groups of cations.

10 drops of the control mixture are poured into a centrifuge tube, 5-6 drops of ammonium buffer mixture and 15 drops of (NH 4) 2 CO 3 are added. The resulting precipitate (II group of cations) is centrifuged, 2-3 drops of (NH 4) 2 are added to the solution above the precipitate CO 3 (test reaction). If a white cloud forms, add 5-6 drops of (NH 4) 2 CO 3 and centrifuge, pour the solution into another test tube and write that this is group I cations. A quarter of a test tube of water is added to the sediment. Shake out and centrifuge again. The solution is poured into the sink, 3-4 drops of CH 3 COOH are added to the sediment. If the precipitate has not dissolved, heat it in a water bath and add 2 more drops of CH 3 COOH, i.e. try to dissolve in the smallest possible amount of acetic acid. After dissolving the precipitate, the solution is diluted with 5 drops of water, poured into another test tube and labeled as group II cations.

3. Opening Ba 2+ .

2-3 drops of a solution of group II cations are poured into a centrifuge tube, 2 drops of CH 3 COON and 3-4 drops of potassium dichromate are added. A yellow precipitate indicates the presence of Ba 2+ cations.

4. Removal Ba 2+ and opening Ca 2+ .

The centrifuge tube with the BaCrO 4 precipitate is centrifuged, the solution is poured into another tube and 3-4 drops of ammonium oxalate are added. If a white precipitate is formed, then the Ca 2+ cation is present.

5. Opening Mg 2+ .

2-3 drops of group I solution are poured into the test tube, 2 drops of ammonium buffer mixture and 3-4 drops of sodium hydrogen phosphate are added. If a white precipitate forms, then Mg 2+ cation is present.

6. Removal N.H. 4 + and opening K + .

Add 2-3 drops of a group I control solution to a centrifuge tube, add 1 drop of phenolphthalein, 5 drops of formalin and drop by drop a Na 2 CO 3 solution until the solution turns red. The mixture is heated for 1 minute, cooled and decolorized by adding acetic acid dropwise. If turbidity forms, the mixture is centrifuged, the solution is poured into another test tube and 3-4 drops of sodium cobaltinite are added to it. If a yellow precipitate is formed, then a potassium cation is present.

Laboratory work No. 4

Cation reactions III groups.

Group III includes cations Fe 2+, Fe 3+, Ni 2+, CO 2+, Mn 2+ cations of the Al 3+ subgroup and other cations of trace elements.

Cation reaction Fe 2+ .

1. Fe 2+ with potassium hexacyanoferrate K 3 forms a “Turnboole blue” precipitate.

3 Fe 2+ +2K 3 →Fe 2 +6K +

In this reaction, add 3-4 drops of K 3 to 1-2 drops of iron sulfate (+2). A precipitate of blue light is formed, greenish around the edge of the test tube.

2. Reaction with alkalis:

Fe 2+ +KOH - →Fe(OH) 2 ↓

Add 3-4 drops of alkali solution (KOH, NaOH) to 2-3 drops of Fe 2+. A dirty green precipitate forms.

Cation reactions Fe 3+

1. Reaction with K 4 (potassium hexocyanoferrate).

4Fe 3+ +3 4 - →Fe 4 3 ↓

Add 3-4 drops of K4 solution to 2-3 drops of Fe 3+. A blue precipitate of “Prussian blue” is formed.

2. Reaction with ammonium thiocyanate NH 4 CHS.

Fe 3+ +3NH 4 CNS→Fe(CNS) 3 +3NH 4 +

Add 3-4 drops of ammonium thiocyanate to 1-2 drops of Fe 3+. A blood-red solution is formed.

Cation reactions Ni 2+ .

1. Reactions with Chugaev’s reagent (dimethylgleoxime)

To 2-3 drops of Ni 2+ add 2-3 drops of dimethyl gleoxime and 1-2 drops of diluted NH 4 OH. A bright red precipitate forms. The determination of Ni 2+ is interfered with by Fe 2+ cations, which must first be removed.

2.Reaction with alkalis:

Ni 2+ +2OH - →Ni(OH) 2 ↓

Add 2-3 drops of alkali to 2-3 drops of Ni 2+. A green precipitate forms.

Reactions of Co 2+ cations

1.Opening of potassium nitrite KNO 2:

Co 2+ +7NO 2 - +3K + +2CH 3 COOH→K 3 [CO(No 2) 6 ]↓+NO+2CH 3 COO - +H 2 O

To 2-3 drops of Co 2+ add 1 spatula of dry salt KNO 2 and 1 drop of CH 3 COOH. This produces a yellow precipitate.

2. Discovery of ammonium thiocyanate NH 4 CNS:

Co 2+ +4CNS - →[Co(CNS) 4 ] 2-

To 2-3 drops of Co 2+ add 5 drops of a saturated solution of NH 4 CNS and 1 spatula of dry salt NH 4 CNS.

A bright blue solution is formed.

Cation reactions Mn 2+ .

1. Discovery of sodium bismuthate NaBiO 3:

2Mn 2+ +5NaBiO 3 +14H + →2MnO 4 - +5Bi 3+ +5Na + +7H 2 O

In this reaction, to 1-2 drops of Mn 2+ add 3-4 drops of 6N nitric acid, 3-4 drops of water and dry salt NaBiO 3 on the tip of a spatula. A crimson-red solution is formed above the precipitate.

2. Opening with lead dioxide PBO 2:

2Mn 2+ +5PbO 2 +4H + →2MnO - 4 +5Pb 2+ +2H 2 O

To 1 drop of Mn 2+ add 1 spatula of PbO 2 and 5-6 drops of concentrated nitric acid.

A violet-red solution is formed.

Laboratory work No. 5

Analysis of a mixture of cations III groups.

1. Discovery of Fe 2+ cations:

Add 3-4 drops of K3 to 2-3 drops of the control mixture. A blue precipitate indicates the presence of Fe 2+ cations.

2. Discovery of Fe 3+ cations:

Add 3-4 drops of K4 to 2-3 drops of the control mixture. If a blue precipitate is formed, then Fe 3+ cations are present in the solution

3.Discovery of Ni 2+ cations:

Add 3-4 drops of dimethylgleoxime and 1-2 drops of NH 4 OH to 2-3 drops of the control mixture. If a bright red precipitate is formed, then nickel cations are present.

If Fe 2+ cations are present in the control solution, then under these conditions they also react with dimethyl gleoxime and form a red precipitate.

In this case, the reaction is performed on filter paper. 1 drop of ammonium buffer mixture, 1 drop of Na 2 HPO 4, and 1 drop of control mixture are poured into the center of the filter. When adding each drop, wait until the drop dissolves, and hold the filter horizontally in your hand. Under these conditions, iron cations, forming a precipitate with sodium hydrogen phosphate, remain in the center of the filter, and nickel cations are absorbed at the periphery of the filter. Add 1 drop of water to wash away the remaining nickel on the periphery of the filter. A pipette containing dimethylgleoxime is passed along the inside of the wet spot. If nickel cations are present, a red ring is formed.

4. Discovery of Co 2+ cations:

To 2-3 drops of the control mixture add 1 spatula of NaNO2, 2-3 drops of KCl, and 1-2 drops of CH3COOH. If a yellow precipitate is formed, then cobalt cations are present.

5. Discovery of Mn 2+ cations.

Add 3-4 drops of 6N HNO 3 and 3-4 drops of water to 2-3 drops of the control mixture. Add 1 spatula of dry salt NaBiO 3 to the mixture. If a red solution forms above the precipitate, then manganese cations are present.

Laboratory work No. 6

General characteristics of anions

Anions are divided into III analytical groups. Group I includes the anions CO 3 2-, HPO 4 2-, SO 4 2-, SO 3 2-, CrO 4 2- and others. Group reagent for group I of BaCl 2 anions, which precipitates them in a neutral and slightly alkaline environment, forming white precipitation.

Group II includes the anions Cl - , Br - , J - , S - , CNS - , CN - and others. They are precipitated by the group reagent AgNO 3 from weakly acidic solutions.

Group III includes the anions NO 3 -, NO 2 -, CH 3 COO -, ClO 3 -, MnO 4 - and others. Barium and silver salts Group III anions are soluble in water and do not have a group reagent.

Anion reactions I groups.

When group I anions are treated with a BaCl 2 solution, precipitates are formed that are soluble in various acids. We will use this to detect group I anions.

1. CO 3 2 + BaCl 2 → BaCO 3 ↓ +2Cl -

Add 2-3 drops of CO 3 2- and 2-3 drops of BaCl 2 to form a white precipitate soluble in acetic acid with the release of gases:

↓ BaCO 3 +2CN 3 COOH → Ba(CH 3 COO) 2 + H 2 O + CO 2

2. HPO 4 2‑ + BaCl 2 → BaHPO 4 ↓ + 2Cl -

Barium hydrogen phosphate precipitate dissolves in strong acids without releasing gas:

↓ BaHPO 4 + 2НCl → BaCl 2 + H 3 PO 4

3. Acid sulfate also forms a white precipitate with BaCl 2, but it is not soluble in any acids.

SO 4 2- + BaCl 2 → BaSO 4 ↓ + 2Cl -

Add 2-3 drops of BaCl 2 solution to 2-3 drops of SO 4 2-. A white precipitate is formed, insoluble in acids.

Anion reaction II groups

Group II anions (Cl - , J -) form white and yellow precipitates with AgNO 3.

1. Cl - + AgNO 3 → AgCl ↓+ NO 3 -

Add 2-3 drops of AgNO 3 solution to 2-3 drops of Cl - ions. A white precipitate forms. If 3-4 drops of NH 4 OH are added to the precipitate, the precipitate dissolves, forming an ammonia complex:

AgCl ↓ + 2 NH 4 OH → Cl + 2H 2 O

2. J - + AgNO 3 → AgJ↓ + NO 3 -

Add 2-3 drops of J- ions to 2-3 drops of AgNO 3 to form a yellow precipitate insoluble in NH 4 OH

To make sure that J - is present, use its reaction with Pb(NO 3) 2

2J - + Pb(NO 3) 2 → PbJ 2 ↓ + 2NO 3 -

Add 2-3 drops of J- ions to 2-3 drops of Pb(NO 3) 2 to form a bright yellow precipitate.

Anion reaction III groups

Group III anions (NO 3 - and CH 3 COO -) do not have a group reagent and can be opened by a fractional method, i.e. the discovery of one ion is not interfered with by another.

Anion opening reaction NO 3 -

Reaction with ferrous sulfate.

2NO 3 - + 2Fe 2+ + 8H + → 2Fe 3+ + 2NO + 4H 2 O

To 2-3 drops of NO 3 - add 2 spatulas of dry salt FeSO 4 and 3-4 drops of concentrated sulfuric acid. NO gas is formed which, oxidized by atmospheric oxygen, turns from colorless to brown:

2NO + O 2 → NO 2

Anion opening reaction CH 3 SOO -

Reaction of opening of CH 3 COO ions - iron (III) chloride

FeCl 3 + 3CH 3 COONa → Fe (CH 3 COO) 3 + 3NaCl

Add 1-2 drops of ferric chloride to 2-3 drops of acetate ions. A reddish solution is formed.

Laboratory work No. 7

Analysis of a mixture of anions of three groups

Add 2-3 drops of BaCl 2 to 2-3 drops of the control mixture. If a white precipitate is formed, then group I anions are present. Add 3-4 drops of acetic acid to the precipitate. If the precipitate dissolves to form CO 2 gas, carbonate anions are present. If the precipitate does not dissolve, then add 2-3 drops of nitric acid. If the precipitate dissolves, then hydrogen phosphate anions are present; if it does not dissolve, then sulfate ions are present.

2. Discovery of group II anions.

Add 2-3 drops of AgNO 3 to 2-3 drops of the control mixture. If a precipitate forms, then group II anions are present. 3-4 drops of ammonium hydroxide are added to the precipitate. If the precipitate is completely dissolved, then chlorine anions are present. If the precipitate does not dissolve, then it is centrifuged, the solution is poured into another test tube and 2-3 drops of nitric acid are added. If a white precipitate forms again, then chlorine ions are present.

To determine iodine ions, add 2-3 drops of lead nitrate to 2-3 drops of the control solution. If a bright yellow precipitate is formed, then iodine ions are present.

3. Analysis of group III anions.

Nitrate and acetate ions are determined by the reactions indicated above, i.e. nitrate ion by the action of FeSO 4 and concentrated sulfuric acid, and acetate ion by the action of ferric chloride.

Laboratory work No. 8

Dry salt analysis

I . Dissolving dry salt.

Part of the dry salt is transferred to a test tube, a quarter of the test tube is added with water and shaken thoroughly. If the salt does not dissolve, then it is first dissolved in acetic acid, then in nitric acid.

II . Cation analysis.

1. If the salt consists of cations of group III, the formation of a precipitate with ammonium sulfide, then the determination is carried out according to the analysis of a mixture of group III cations.

2. If a precipitate with (NH 4) 2 S does not form, then the cation is either group I or II. In this case, the presence of group II is checked by the action of ammonium carbonate. When a white precipitate is formed, the discovery reactions of barium and calcium are carried out.

2. If the action of ammonium carbonate does not form a white precipitate, then only group I cations are present and the discovery of ammonium, magnesium and potassium cations is carried out.

III . Discovery of anions.

This determination is carried out using the method of analyzing a mixture of anions of three groups, as indicated above.

Laboratory work No. 9

QUANTITATIVE ANALYSIS

Gravimetric method of analysis

Determination of water of crystallization in salt BaCl 2 ∙2 H 2 O

Gravimetric (weight) analysis is carried out using two methods:

1) distillation method

2) deposition method

Determination of water of crystallization is carried out by distillation.

The water included in the crystal structure of some crystalline hydrate substances is called water of crystallization. The content of crystallization water in different crystal hydrates is different and corresponds to certain chemical formulas: H 2 C 2 O 4 ∙2H 2 O, BaCl 2 ∙2H 2 O, CuSO 4 ∙5H 2 O, Na 2 SO 4 ∙10H 2 O, etc. . However, depending on the temperature, air humidity and the nature of the crystalline hydrates, water can erode from the crystals, i.e. quantitatively may decrease or even increase. Therefore, in order to know the exact chemical formula Crystal hydrates are determined by the water of crystallization.

The method is based on the release of water when heated, i.e. using the distillation method. If we consider the example of BaCl 2 ∙ 2H 2 O, then an exact weighed portion of this salt (1-1.% g) is placed in a crucible and heated in a drying oven at 120-125 o C. Until the mass stops changing (drying to a constant mass)

BaCl 2 2H 2 O → BaCl 2 + 2H 2 O

Progress of determination

The porcelain crucible or bottle is thoroughly washed and dried for 5-10 minutes in a drying cabinet and cooled for 20 minutes. in a desiccator and weighed first on technochemical, then on analytical balances.

An exact weighed portion of BaCl 2 ∙2H 2 O salt (1-1.5 g) is placed in a crucible and dried in an oven for 2 hours at 120-125 o C. The crucible with salt is removed with tongs and transferred to a desiccator, cooled for 20 minutes. and weigh it on an analytical balance, recording the mass. The crucible is again placed in the drying cabinet and dried for 1 hour. After cooling the crucible in the desiccator, weigh it again. If the difference in mass is no more than 0.0002 g, the water is considered to be completely removed.

After drying to constant weight, the content of water of crystallization is calculated.

CALCULATIONS:

Let us assume that the weighing results are as follows:

Crucible mass 10.6572 g.

The mass of the crucible with the substance is 11.9746 g.

The weight of salt will be 1.3274 g.

Mass of the crucible with the substance after drying

1st weighing 11.7629

2nd weighing 11.7624

3rd weighing 11.7622

From the weighing results it is clear that the second and third weighings are close enough, so the first result is discarded and the average of the two subsequent ones is taken:

(11,7624+11,7622) / 2 = 11,7623

Based on the difference in the mass of the crucible with the substance before and after drying, the mass of crystallization water is found:

11.9846 - 11.7623 = 0.2223 g.

The percentage of water of crystallization is found from the proportion:

1.3272 g of sample contains 0.2223 g of H 2 O

in 100 g. X 2 H 2 O

TITRIMETRIC ANALYSIS METHODS

Neutralization method

In titrimetric (volumetric) analysis, a solution with a precisely known concentration (titrated or standard solution) is placed in a burette and added dropwise to the test solution with a known volume, placed in a conical flask and constantly stirred. By changing the color of the indicator or other signs, determine the equivalent volume spent on the reaction and substituting its value (V) into the calculation formulas to determine the amount of the substance under study.

The neutralization or acid-base titration method is based on the reaction:

H + + OH - = H 2 O

and allows you to determine the concentrations of acids, alkalis, hydrolyzing salts, etc.

Laboratory work No. 10

Determination of acid percentage

The work is carried out in the following sequence.

1. Preparation of 250 ml of 0.1 normal standard solution of oxalic acid.

2. Preparation of 250 ml of 0.1 normal alkali solution from a 4% solution.

3. Determination of the exact concentration of the prepared alkali.

4. Determination of the percentage of the control acid solution.

Theoretical calculation

1. Calculation of the mass of oxalic acid for the preparation of 250 ml of 0.1 normal solution

M H 2 C 2 O 4 2H 2 O = 126 g.

g-eq. H 2 C 2 O 4 2H 2 O = 126:2 = 63 g.

If: 1000ml - 1g-eq - 1 N

means: 1000 ml - 63 g - 1 N

1000 ml - 6.3 g - 0.1N

250 ml - X g. - 0.1 N

This means that to prepare a 0.1 N solution, measure 1.5757 g of oxalic acid on an analytical balance, transfer it to a 250 ml flask, dissolve it in a small portion of water, add water to the mark and mix thoroughly.

2. Preparation of 250 ml of 0.1 N NaOH solution from a 4% solution.

M NaOH = 40 g. G - eq NaOH = 40 g.

If: 1000 ml - 40 g - 1 N

1000 ml - 4 g - 0.1N

250 ml - X g - 0.1 N

from here: X = (250 4): 1000 = 1 g

This means that to prepare 250 ml of 0.1N NaOH solutions, you need to take 1 g of alkali. But NaOH strongly attracts moisture and it is practically impossible to weigh it on an analytical balance. Therefore, we will prepare the solution from a previously prepared ~ 4% solution. Let's calculate how many ml of 4% NaOH must be taken so that the solution contains 1 g

If 100 ml - 4 g - 4%

X = (100 1): 4 = 25 ml

This means that to prepare 250 ml of a 0.1 N NaOH solution, take 25 ml of a 4% NaOH solution with a graduated cylinder, pour it into a 250 ml flask, add water to the mark and mix thoroughly.

3. Determination of the exact concentration of NaOH

Using a pipette or burette, pour 10 ml of 0.1N oxalic acid into a conical flask, add 1-2 drops of the indicator - phenolphthalein (ph-f) and titrate, adding NaOH solution drop by drop from the burette until a faint pink color appears.

H 2 C 2 O 4 + 2NaOH - Na 2 C 2 O 4 + 2H 2 O

We repeat the experiments 4 times and write the results in the table.

From three close values, we calculate the average result and use the formula to calculate the normality of NaOH:

4. Determination of % acid content.

Add 5-10 ml of control acid to a 250 ml volumetric flask, dilute to the mark with water and mix thoroughly. Using a pipette or burette, take 10 ml of acid, pour it into a conical flask, add 1-2 drops of phenolphthalein and titrate with a working solution of NaOH until the color turns pale pink. The experiments are repeated 4 times and the titration results are recorded in the table.

From three close results, the average is calculated and the percentage of acid is determined using the formula:

Laboratory work No. 11

METHODS OF REDOX TITRATION

Permanganatometry

The method is based on the high oxidizing ability of permanganate ions in an acidic environment, for example Fe 2+ ions according to the reaction:

5Fe 2+ + MnO 4 - + 8H + - 5Fe 3+ + Mn +2 + 4H 2 O

Work order:

1. Preparation of 250 ml of 0.05N solution of KMnO 4 from ~ 3% solution.

2. Determination of the exact concentration of KMnO 4

3. Determination of gram iron content.

Theoretical calculations

1. Calculate how many ml. 3% KMnO 4 solution is needed to prepare 250 ml of 0.05 solution

1000 ml - 1 g - eq - 1N

1000 ml - 31.61 g - 1N

1000 ml - 1.5805 g - 0.05N

250 ml - X g - 0.05N

Our stock solution is 3% therefore:

100 ml - 3 g - 3%

X ml - 0.395 g - 3%

This means to prepare 250 ml. Using a measuring cylinder, take 13.2 ml of a 3% KMnO 4 solution from a 0.05N KMnO 4 solution, pour it into a 250 ml flask, add water to the mark and mix thoroughly.

2. Determination of the exact concentration of KMnO 4: using a pipette or burette, select 5 ml of 0.1N oxalic acid, pour into a conical flask, add 10-15 ml of 10% H 2 SO 4, heat to ~ 80 o C and titrate while hot solution of KMnO 4 until slightly pink in color. After adding 1-2 drops of KMnO 4, mix the mixture thoroughly until it becomes discolored, then continue titrating in the usual way.

5C 2 O 4 2- + KMnO 4 - + 16 H + - KMn 2+ + 8H 2 O + 10СО 2

We repeat the experiments 4 times and from three similar results we take the average and use the formula to calculate the normality KMnO 4

3. Determination of gram content of Fe 2+

Add 10-15 ml of a 10% H 2 SO 4 solution to the control iron solution in a conical flask and titrate with the working solution of KMnO 4 to a pale pink color. After adding 1-2 drops of KMnO 4, mix the solution thoroughly until it becomes discolored and then titrate in the usual way.

Laboratory work No. 12

IODOMETRY

Determination of gram copper content ( Cu 2+ )

The method is based on redox processes associated with the oxidation of J - ions to J 2

2J - - 2e → J 2

The order of work.

1. Preparation of 250 ml of 0.1N solution of K 2 Cr 2 O 7

2. Determination of the concentration of the working solution Na 2 S 2 O 3

3. Determination of gram copper content.

Theoretical calculations

1. Preparation of 250 ml of 0.1N solution of K 2 Cr 2 O 7.

So 1000 ml - 49.03 g - 1N

1000 ml - 4.903 g - 0.1N

250 ml - X g - 0.1N

This means that in order to prepare 250 ml of a 0.1N solution, it is necessary to weigh 1.2257 g of K 2 Cr 2 O 7 on an analytical balance, transfer it to a copper flask, dissolve it in a small amount of water, add water to the mark and mix thoroughly.

2. Determination of Na 2 S 2 O 3 concentration:

5-7 ml of a 20% KJ solution and 1-15 ml of a 10% H 2 SO 4 solution are poured into a conical flask using a graduated cylinder. Using a pipette or burette, add 1 ml of 0.1N K 2 Cr 2 O 7 solution, cover the flask with a watch glass and leave in the dark for 5 minutes to complete the reaction:

Cr 2 O 7 2- + 6J - + 14H + - 3J 2 + 2Cr 3+ + 7H 2 O

The resulting brown J 2 solution is titrated with thiosulfate (Na 2 S 2 O 3) to a straw-yellow color. Then add 5 ml of starch solution and the resulting blue solution is titrated with thiosulfate to a pale green color:

J 2 + 2S 2 O 3 2- - 2J - + S 4 O 6 2-

The experiment is repeated 4 times and the average result is calculated from three close ones and the normality of thiosulfate is calculated using the formula:

3. Determination of gram content of Cu 2+:

15 ml of a 20% KJ solution and 2 ml of 10% K 2 SO 4 are poured into a conical flask with the copper solution being tested from a graduated cylinder, the flask is covered with a watch glass and left in the dark for 5 minutes to complete the reaction:

Cu 2+ + 4J - - 2CuJ↓ + J 2

The resulting brown turbidity is titrated with thiosulfate to a pale yellow color, 5 ml of starch solution is added and titrated until the blue color disappears. The experiments are repeated 4 times, the average result is calculated from close 3 values and the gram content of Cu 2+ is calculated using the formula:

g-equiv Cu 2+ = G-atom = 63.54 g.

Laboratory work No. 13

Complexation methods

In analytical chemistry practice, complexone-III is more often used. This is the disodium salt of ethylene diaminotetroacetic acid, which forms intracomplex compounds with many metal ions.

By adjusting the pH of the medium and selecting the appropriate indicators using complexometry, it is possible to determine many metals, total water hardness, etc.

Indicators used in complexometry are called metallochromic indicators. They also form complexes with metal ions, colored in different colors.

Determination of total water hardness.

The order of work.

1. Preparation of 250 ml ~ 0.1 N solution of complexone - III

2. Determination of the exact concentration of complexone - III

3. Determination of the total hardness of tap water.

1. Preparation of 250 ml of 0.1N solution of complexone-III theoretical calculation.

M K-III = 372 g.

Means: 1000 ml - 186 g - 1N

1000 ml - 18.6 g - 0.N

250 ml - X 2 - 0.1N

This means that to prepare 250 ml of a 0.1N solution on an analytical balance, select 4.65 g of complexone III, transfer it to a 250 ml flask, dissolve it in a small volume of water, then add water to the mark and mix thoroughly.

2. Determination of the exact concentration of complexone III

Using a pipette or burette, take 10 ml of a 0.1N solution of zinc nitrate or chloride into a conical flask, add 10-15 ml of an ammonium buffer mixture, at the tip of the staple there is a black chromogen indicator and titrate the resulting red solution with complex-III to a blue color. From the four determinations, we take the average result of three similar results and calculate the normality of complexone III using the formula:

3. Determination of total water hardness.

Pour 100 ml of tap water measured with a measuring cylinder into a conical flask, add 10-15 ml of ammonium buffer mixture, a black chromogen indicator at the tip of the staple and titrate the reddish solution with complexone III until blue.

We repeat the definition four times and write the results in the table. From three similar results, we calculate the average and calculate the total water hardness using the formula:

LITERATURE

1. Mirkamilova M.S. “Kimyo Analyst”, Tashkent, 2003.

2. Mirkomilova M.S. “Analyst Kimyo”, Tashkent, 2000.

3. Vasiliev V.P. "Analytical Chemistry" 1-2 volume. M., Chemistry, 1089

4. Alekseev V.N. Course of qualitative chemical microanalysis. M., Chemistry, 1972

5. Alekseev V.N. "Quantitative Analysis". M., Chemistry, 1972

6. Kreshkov A.N. “Fundamentals of Analytical Chemistry” vol. 1-2. M., Chemistry, 1965