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LMCHE 102: CHEMISTRY LAB

LABORATORY MANUAL CHE102 CHEMISTRY LAB

1

LMCHE 102: CHEMISTRY LAB

Table of Contents S.No1

Title of ExperimentWith the help of complexometeric titration how you will determine the hardness of given hard water sample by using EDTA. Provided standard hard water.(1ml of S.H.W.=1mg of CaCO3)

Page No.3-4

2

Preparation compound.

of

sodium

trioxalatoferrate(III)

Na2[Fe(C2O4)3]

.9H2O

5-6

3

To find the distribution coefficient of benzoic acid between benzene and water.

7-9

4 5

Determination of the dissociation constant of acetic acid using pH-meter. Determination of Strength of hydrochloric acid solution(approximately N/10) by titrating it against sodium hydroxide solution conductometrically To test the validity of Beer-Lamberts law using colorimeter and to determine unknown concentration of solution

10-12 13-16

6

17-20

7 8

Estimation of nickel in the given sample using dimethyl glyoxime. Determination of the rate constant of hydrolysis in case of ethyl acetate using an alkali.

21-22 23-26

9

Determine the strength of given solution of ferrous ammonium sulphate by titrating against potassium dichromate solution

27-28

10

Separation

of

a

mixture

of

organic

compounds

by

thin

layer

29-31

chromatography. 11 To determine the surface area of given solid by adsorption of acetic acid from its aqueous solution. 32-36

Textbook:

1. J. Mendham, R. C. Denney, J. D. Barnes, and R. C. Denney, Vogels Quantitative Chemical Analysis, 6 Edition, Prentice Hall, 2000. (Physical Chemistry)th

Other Reading: 2. J. B. Yadav, Advance Practical chemistry, Krishna Publications, Merrut 12 Revised Edition 3. Basset J Denny. R. C., Jeffery C. H. and Mendham J., Vogels Textbook of Quantitative Inorganic analysis, ELBS, 1978. (Inorganic) 4. N. K. Vishnoi Advanced Practical Organic Chemistry, Vikas Publications, New nd Delhi, 2 edition 5. M.S. Saini, Senior practical chemistry-Vol-III, Modern Publishers-2006th

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LMCHE 102: CHEMISTRY LAB

Experiment No. 1 Title: TO DETERMINE THE HARDNESS OF THE GIVEN HARD WATER SAMPLE BY EDTA METHOD. PROVIDED STANDARD HARD WATER. (1 mL of S.H.W.=1 mg of CaCO3). Equipments to be used: Burette, Titration flask, Pipette, Beakers, funnel Chemicals Used: Standard Hard water, EDTA solution, EBT, Buffer Solution Learning Objectives: (i) The purpose of this experiment is to determine the hardness of water by measuring the concentrations of calcium and magnesium in water samples by titration. (ii)To know about use of buffer solution: The buffer being used has composition NH4Cl and NH4OH. Its pH is the order of 10.5. (iii) How the indicator works: When indicator is added to hard water it combines with free metal ions present in water. HIn-2 + M+2 MIn- + H+ (Wine red) When EDTA solution is added to the titration flask it combines with the free metal ions giving metal EDTA complex, which is stable and colorless. H2Y2- + M+2 MY-2 + 2H+ {M = Mg or Ca}

When all the free metal ions are exhausted, next drop of EDTA removes the metal ion engaged with indicator and the original blue colour is restored. H2Y2- + MIn+ Procedure: MY-2 + HIn+2 + H+

(a).Standardisation of EDTA solution: Pipette out 10ml of standard hard water in the titration flask. Add to it 2-3ml of buffer solution and two drops of Eriochrome Black-T indicator. A wine red colour appears. Titrate this solution against EDTA solution taken in a burette till wine red colour changes to blue colour. This is the end point. Recovered the volume of EDTA consumed as A ml. Repeated the procedure to get at least three concordant readings. (b). Determination of Total Hardness:-

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LMCHE 102: CHEMISTRY LAB

Pipette out 50ml of tap water in the titration flask. Add to it 5-6 ml of buffer solution and four drops of Eriochrome Black-T indicator. A wine red colour appears. Titrate this solution against EDTA solution taken in a burette till wine red colour changes to blue colour. This is the end point. Recovered the volume of EDTA consumed as B ml. Repeated the procedure to get at least three concordant readings Calculations:

(a).Standardisation of EDTA solution:1 ml of standard hard water 10 ml of S.H.W. A ml of EDTA I ml of EDTA = 1 mg of CaCO3 = A ml of EDTA

= 10 mg of CaCO3 = 10 mg of CaCO3

= 10/A mg of CaCO3

(b).Calculation of total hardness: 50 ml of hard water sample Now 1 ml of EDTA 50 ml of hard water sample 1 ml of hard water sample = B ml of EDTA = 10/A mg of CaCO3 = B x 10/A mg of CaCO3. = B x 10/A x 1/50 mg of CaCO3.

1000 ml of hard water sample = B x 10/A x 1/50 x 1000 mg of CaCO 3. Hence total hardness = 200 x B/A ppm

Result: The hardness of water is........... Scope of result: The determination of water hardness is a useful test that provides a measure of quality of water for households and industrial uses. Originally, water hardness was defined as the measure of the capacity of the water to precipitate soap.

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LMCHE 102: CHEMISTRY LAB

Experiment No. 2 Title: Preparation of Sodium trioxalato ferrate(III) EQUIPMENTS TO BE USED: China dish, water bath, glass rod, Buchner funnel, glass funnel, weighing machine. CHEMICAL REQUIRED: Mohrs Salt ((NH4)2SO4FeSO46H2O), 3M H2SO4, oxalic acid, water, ethanol, 30% H2O2, acetone. LEARNING OBJECTIVES: (i) To know about gravimetric analysis of ions (ii) The students will learn how the transition complex formation is helpful to determine amount of particular ion in given salt. (iii) How to use sintered glass crucible and suction pump. THEORY: Sodium trioxalato ferrate (III) is a coordination compound; with a coordination number of six and oxidation state of +3. The shape of the complex is octahedral and it is sp3d2 hybridized. Na3[Fe(C2O4)3] 3H2O is highly photosensitive. The bright green crystals on exposure soon become covered with a yellow powder of ferrous oxalate. 2Na3[Fe(C2O4)3]3H2O 2FeC2O42H2O + 2CO2 + 3Na2C2O4 + 2H2O PROCEDURE: Preparation of Ferrous Oxalate: Weigh ferrous ammonium sulphate (Mohrs Salt) (NH4)2SO4FeSO46H2O.Transfer the ferrous ammonium sulphate to a beaker containing 25 mL of warm water acidified with 1 mL dilute 3M H2SO4. Dry the vial and weigh the empty vial. Record the mass of ferrous ammonium sulphate used. To this solution add 25 mL of oxalic acid solution (5 g/50mL). Cautiously heat the solution to boiling on a hot plate, continuously stirring the solution to avoid bumping. Remove and then allow the precipitate to settle. Decant and discard the clear supernatant liquid (avoid loss of precipitate). Stir the remaining precipitate with 25 mL of hot water, the solubility of FeC2O42H2O is .022 g/100 mL in cold water and .026 g/100 mL in hot water. Decant and discard the wash liquid. Add 25 mL of hot water to the precipitate and stir, then filter by suction using a small Buchner funnel and wash the precipitate thoroughly with small portions (10-20 mL) of hot water. Finally rinse with 20 mL of acetone. Weigh the final product.5

LMCHE 102: CHEMISTRY LAB

Preparation of Sodium trioxalato ferrate(III): Suspend the washed and dried ferrous oxalate in 30 mL of warm solution containing 3.5 g of Sodium oxalate (Na2C2O4H2O). Place this solution in an ice bath and add slowly with continuous stirring 7-10 mL of 30% H2O2 in very small portions, then heat the mixture to boiling and dissolve the precipitate by adding in one portion 7 mL of a solution of oxalic acid (containing 2.5 g/25 mL). A further 3 mL is then added drop by drop using an eye dropper (an excess of oxalic acid is to be avoided). The liquid should be near the boiling point while these additions are being made. Filter through a Buchner funnel. Transfer the hot solution to a clean beaker and while still hot, add to the filtrate 15 mL of 95% ethanol and redissolve any precipitated crystals by gently heating. Then store the solution in a dark cupboard for crystallization. After crystallization has occurred, filter with suction and wash the product on the filter paper with 20 mL of an equi-volume mixture of ethanol and water and finally with 20 mL of acetone. Draw air through the precipitate for several minutes. Weigh the dry crystals. RESULT: Colour of the compound. Weight of the ppt. . SCOPE OF THE RESULT: Gravimetric analysis is helpful in estimation of amount of Fe in given complex.

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LMCHE 102: CHEMISTRY LAB

Experiment-3 Title: To study the distribution of benzoic acid between benzene and water. EQUIPMENTS REQUIRED: Pipette, Burette, titration flask, eight washed empty bottles, stoppers, separating funnel. CHEMICAL REQUIRED: Phenolphthalein. Benzene, Benzoic acid, water, NaOH, HCl,

LEARNING OBJECTIVE: In this experiment we will use the volumetric technique of acid-base titration to determine the distribution of benzoic acid in the water-benzene system. From these distribution measurements we will be able to examine the two equilibria: (1) dimerization of benzoic acid in benzene and, (2) distribution of benzoic acid monomers between water and benzene. INTRODUCTION: Distribution coefficient (D) is the ratio of concentrations of a compound in the two phases of a mixture of two immiscible solvents at equilibrium. Hence these coefficients are a measure of differential solubility of the compound between these two solvents. A general treatment by Moelwyn-Hughes1 allows examination of the above two equilibria from distribution measurements. The benzoic acid water-benzene system has been studied by Huq and Lodhi. This treatment has been extended to other acids (e.g. acetic and propionic acids) distributed between water and othe