Second chapter solved MCQs with explanation (Experimental Techniques in chemistry)
1: A filtration process could be very time consuming if it were not aided by a gentle suction which is developed:
Table of Contents
a) If the paper covers the funnel up to its circumference.
B) If the paper has got small-sized pores in it.
c) If the stem of the funnel is large so that it dips into the filtrate.
d) If the paper fits tightly.
Explanation
The right answer is (d).
Gentle suction is developed if filter paper is properly fitted in the funnel. Otherwise, due to spurts of air, there will be no proper suction and then it will be a wastage of time. So (d) is correct.
Related: First Chapter Solved Exercise MCQs Of FSc First-Year Chemistry
2: During the process of crystallization, the hot saturated solution:
a) Is cooled very slowly to get large-sized crystals.
b) Is cooled at a moderate rate to get medium-sized crystals.
c) Is evaporated to get the crystals of the product.
d) Is mixed with an immiscible liquid to get the pure crystals of the product.
Explanation
sizes of crystals depend upon the rate of cooling the hot saturated solution. The higher the rate of cooling, the smaller will be the size of crystals and vice versa. So, a hot saturated solution is cooled at a moderate rate to get medium-sized crystals. Hence, option (b) is correct.
3: Solvent extraction is an equilibrium process and it is controlled by:
a) Law of mass action
b )The amount of solvent
c) Distributive law
d) The amount of solute
Explanation
solvent extraction is an equilibrium process in which a substance dissolved in two immiscible liquids is distributed in such a way that the ratio of its concentrations in each liquid is constant. This is called distributive law.
4: Solvent extraction method is a particularly useful technique for separation when the product to be separated is:
a) Non-volatile or thermally unstable
b) Volatile or thermally stable
c) Non-volatile or thermally stable
d) Volatile or thermally unstable
Explanation
The compounds which are volatile and decomposed on heating can safely be separated without decomposition by solvent extraction. So option (c) is correct.
5: The comparative rates at which the solutes move in paper chromatography, mainly depends upon:
a) The size of paper used
b) Temperature of experiment
c) The Rf values of solutes
d) Size of chromatographic tank used
Explanation
In paper chromatography, the rate at which the solutes move depends upon the ratio of distance travelled by component to the distance travelled by the solvent. This is called Rf (retardation factor) value which is specific for each component. Hence, option (c) is correct.