EXERCISE 1B

Zinc or aluminium do not corrode because:

Three beakers labelled as A, B, and C, each containing $25 \mathrm{mL}$ of water. A small amount of $\mathrm{NaOH}$, anhydrous ${\mathrm{CuSO}}_4$ and $\mathrm{NaCl}$ were added to the beakers A, B and C respectively, it was observed that there was an increase in the temperature of the solutions contained in beakers A and B. Whereas, in case of beaker C, the temperature of the solution fell. Which one of the following statement(s) is (are) correct?

(i) In beakers A and B, an exothermic process has occurred.

(ii) In beakers A and B, an endothermic process has occurred.

(iii) In beaker C, an exothermic process has occurred.

(iv) In beaker C, an endothermic process has occurred.

A dilute ferrous sulphate solution was gradually added to a beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?

Which among the following is (are) double displacement reaction(s)?
(i) $\mathrm{Pb}+{\mathrm{CuCl}}_2\to {\mathrm{PbCl}}_2+\mathrm{Cu}$
(ii) ${\mathrm{Na}}_2{\mathrm{SO}}_4+{\mathrm{BaCl}}_2\to {\mathrm{BaSO}}_4+2\mathrm{NaCl}$
(iii) $\mathrm{C}+{\mathrm{O}}_2\to {\mathrm{CO}}_2$
(iv) ${\mathrm{CH}}_4+2{\mathrm{O}}_2\to {\mathrm{CO}}_2+2{\mathrm{H}}_2\mathrm{O}$

Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?
(i) It is an endothermic reaction.
(ii) It is an exothermic reaction.
(iii) The $\mathrm{pH}$ of the resulting solution will be more than seven.
(iv) The $\mathrm{pH}$ of the resulting solution will be less than seven.

The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is $\mathrm{x}:1$. What is the value of $\mathrm{x}$? $\left(2 / 3 / 4\right)$

Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not.

What is meant by rusting? With labelled diagrams describe an activity to find out the conditions under which iron rusts