Section A
Q1. Answer all of the following questions :
(a)
Rewrite the following statement(s) if you find it/them incorrect :
Over the ionic strength range 0-0.1 M-
(i) activity coefficients increase with increasing ionic strength;
(ii) activity coefficients increase with increasing ionic charge.
(b) The molarity of C_{29}H_{60} in winter rainwater is 5.6 nM. Find its concentration in parts per billion (ppb).
(c)
You have been asked to prepare a buffer solution with an alkaline pH by mixing ammonium chloride and aqueous ammonia from the following sets of solutions :
(i) 50 ml solutions of 0.001 molar NH4Cl and 0.003 molar aqueous ammonia
(ii) 50 ml solutions of 0.1 molar NH4Cl and 0.3 molar aqueous ammonia
Will both of them work? If not, which one will work efficiently and why?
(d) During an acid-base titration experiment, a student noticed some drops of acid on the inside of the neck of the conical flask. The student decided to wash the drops into the main solution using distilled water. Briefly explain whether the action will have any consequences on the outcome of the titration.
(e) In flame photometry, the analysis of analyte is carried out only in an interzonal region of the flame but not in the outer cone or primary combustion zone of the flame. Justify.
(f) Explain the proximate analysis of coal. How do you estimate manganese present in a steel sample volumetrically?
(g) What is a gradient elution development in chromatography?
(h) Calculate the degree of hydrolysis and pH of 0.01 M Na2CO3 solution.
