21.
Statement I A thermally insulated vessel contains some water. If the vessel is shaken vigorously, the temperature of the water will rise.
Statement II In this process energy is given to the water.
Which one of the following is correct with reference to the above statements?

22.
Consider the following statements regarding a motor car battery.
1. The voltage is usually 12 V.
2. Electrolyte used is hydrochloric acid.
3. Electrodes are lead and copper.
4. Capacity is expressed in ampere hour.
Which of the above statement are correct?

25.
Assertion (A) For a galvanic cell, oxidation takes place at anode and reduction at cathode.
Reason (R) Electrons in the external circuit move from anode to cathode

26.
Match List-I with List-II.
List-I List-II
a. Endothermic 1. Variation of enthalpy of a reaction with temperature
b. Exothermic 2. A process or reaction which consumes heat
c. Activation energy 3. A process or reaction that releases heat
d. Arrhenius equation 4. The amount of energy which must be invested in a reaction to get it started
Select the correct answer:

27.
When items of jewellery made of metals such as copper or nickel are placed in a solution having a salt of gold, a thin film of gold is deposited by

30.
When two plates of different metals are placed in an electrolyte, the developed emf between them depends on