Calcutta University BSc II (Chemistry)

Unit II. Basic physical chemistry VI

Practice Questions:

1.       Define the term oxidation and reduction.

2.       A positron has a mass number of _____, a charge of _____, and a mass equal to that of a(an) _____.

3.       The lead-containing reactant(s) consumed during recharging of a lead-acid battery is/are __________.

4.       How many grams of CuS are obtained by passing a current of 12 A through a solution of CuSO4

for 15 minutes __________ ?

5.       Why every combustion reaction is an oxidation-reduction reaction?

6.       What is the function of the electrolyte in a galvanic cell?

7.       Molten AlCl₃ is electrolyzed for 5.0 hours with a current of 0.40 amperes. Metallic aluminum is produced at one electrode and chlorine gas, Cl₂, is produced at the other. How many liters of Cl₂ measured at STP are produced when the electrode efficiency is only 65%?

8.       What is the value of E for the half-cell:
MnO₄^- (0.010 M) + 8H⁺ (0.20 M) + 5e^-  Mn²⁺ (0.020 M) + 4H₂O?

9.       What is the oxidation number of potassium in KMnO₄?

10.   What is the difference between a storage battery and a fuel cell?

11.   What is a PEM fuel cell?

12.   What reaction prevents us from using Zn as an electrode of the first kind in acidic solutions? Which other electrodes of the first kind would you expect to behave in the same manner as Zn when immersed in an acidic solution?

13.   Explain why each of the following decreases the analysis time for controlled-potential coulometry: a larger surface area for the working electrode, a smaller volume of solution, and a faster stirring rate.

14.   Write Nernst equation for Fe⁺³ and Fe⁺².

15.   Write the reactions occurring at the anode and the cathode for the potentiometric electrochemical cell with the following shorthand notation.

Pt(s) |H₂ (g) H⁺ (aq) ||Cu²⁺(aq ) |Cu(s)