Introduction To Classical Analysis And Separation Technique Question Paper

Introduction To Classical Analysis And Separation Technique

Course:Bachelor Of Science

Institution: Kenyatta University question papers

Exam Year:2009

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2008/2009
INSTITUTE OF OPEN LEARNING (IOL)
EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE AND
BACHELOR OF EDUCATION

SCH 103:
INTRODUCTION TO CLASSICAL ANALYSIS AND
SEPARATION TECHNIQUE

DATE: Thursday, 13th August, 2009

TIME: 2.00 p.m. – 4.00 p.m.
------------------------------------------------------------------------------------------------------------
INSTRUCTIONS:
Answer ALL the questions. Show how you obtained your answers.
1.
a)
Differentiate between the following:
i)
Determinate and indeterminate error
ii)
Distribution ratio and partition coefficient
iii)
Confidence limit and confidence interval
iv)
Direct and indirect titration
(8 marks)

b)
i)
What is a masking agent?
ii)
Under what condition is a masking agent required in an analysis?
(5 marks)
c)
Replicate analysis of a calcite sample yielded CaO percentages as follows:
56.23, 56.00, 56.04, 56.95, 56.08 and 55.68.
i)
determine if 55.68 is an outlier using Q test, 4d test and 3S tests.
ii)
Calculate the mean and the standard deviation

Page 2 of 3

iii)
What is the 95% confidence level and interval of the results.
(8 marks)
d)
Explain four necessary conditions for titration analysis to be successful.
(4 marks)

2.
a)
Why is it difficult to use precipitation technique for separation of trace
elements?
(4
marks)

b)
Explain three sources of impurities in gravimetric analysis and ways of
minimizing
the
impurities.
(5
marks)

c)
50.0 mls of HC1 solution required 20.72 mls of 0.0196 M Ba(OH)2 to
reach end point using bromocresol as indicator. Write a balanced
equation for the reaction. Calculate the molarity of HC1. (5 marks)

d)
Why is it important to remove interferences before carrying out a chemical
analysis

(2 marks)

e)
Briefly explain how solvent extraction works. Under what conditions can
one obtain complete separation of solute which is slightly soluble in the
extracting
solvent?
(4
marks)
f)
Given a solution containing the following molecules: KNO3, LiNO3,
NaNO3 and CsNO3, what analytical method would you use to separate
them? Why would you choose the method?

(4 marks)

3.
a)
The distribution ratio of a compound X between Hexane and water is 10.
Calculate the moles of X remaining in the aqueous phase after 50 mls of
0.2 M solution of X is extracted with the following quantities of
chloroform.
i)
One 50 ml portion
ii)
Two 25 ml portions
iii)
Five 10 ml portions
iv)
What conclusion can you draw from the above results
(6 marks)

Page 3 of 3

b)
Why is it important that both sample and standard be placed on the same
plate in thin layer chromatography?

(5 marks)

c)
A compound A moved 10.5 cm from the point of application on paper
chromatography, while the solvent front moved 18.0 cm beyond the point
of application. Calculate Rf for the compound X. On an identical paper
and conditions, the solvent front moved 14.1 cm beyond the point of
application. Where should the compound X be located?
(5 marks)

d)
i)
Why is separation important to analytical chemists?

ii)
Briefly explain two different methods of separation

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