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National Open University Exam Past Question – CHM 413 OCTOBER/NOVEMBER 2014 EXAMINATION

NATIONAL OPEN UNIVERSITY OF NIGERIA CHM 413 – ANALYTICAL CHEMISTRY II

14-16 AHMADU BELLO WAY, VICTORIA ISLAND LAGOS SCHOOL OF SCIENCE AND TECHNOLOGY OCTOBER/NOVEMBER 2014 EXAMINATION

 

 

Question 1

CHM 413 – ANALYTICAL CHEMISTRY II INSTRUCTION: Six questions to answer four Duration: 2 hours

 

1a) List and explain Four procedures available in handling systematic errors.       (10 marks)

  1. b) Distinguish between accuracy and precision.  (5 marks)

1

 

  1. c) Explain the term ‘pH’ of a solution  (2 2

marks)

 

 

Question 2

The concentrations of copper metal in ten different floodwater samples are as follows:

87.4, 23.3, 17.3, 40.7, 45.3, 69, 58.6, 40.5, 33.5, 89.5.    Determine

  1. i) Mean                                                                                                                           (3 marks) ii)    Median                                                                                                                         (3 marks) iii)   Standard deviation                                                                                                    (6 marks)
2
  1. iv) The 95% confidence limits for the true pH                                                            (5  1  marks)

 

 

Question 3

1

  1. a) Describe the basic principle of Potentiometric titration (7 2 marks)
  2. b) Explain briefly five factors which effects conductivity of an electrolyte (10 marks)

 

Question 4

  1. a) Differentiate between positive and negative correlation               (5 marks)
  2. b) The concentrations of two soil parameters are presented below;

 

Zinc (g ml-1): 2.1 5.0 9.0 12.6 17.3 21.0 24.7
Sulphate (g ml-1): 2 4 6 8 10 12

 

Determine the correlation coefficient,  r.

 

 

Question 5

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2

(12  1  marks)

 

 

1

 

  1. a) Differentiate between thin layer chromatography and column chromatography. (9 2 marks)
  2. b) Describe the basic difference between Electromagnetic radiation analytical techniques and ion exchange technique. (4 mark each; total of 8 marks)

 

Question 6

1

  1. a) State the Kohlrausch law of independent migration of ions                               (3 2  marks)
  2. b) Explain briefly the two application of Kohlrausch law of independent migration of ions (5 marks)

 

-2                    -2

3+.

 

  1. c) A solution is 10-3M in Cr2O7

and 10

M inCr

If the pH is 2.0, what is the potential of the half

 

reaction?                                                                                                                   (9 mark)

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