Complete and balance the following chemical equations :

(i) $\text{NaOH}_{(aq)} + \text{Zn}_{(s)} \rightarrow$

(ii) $\text{CaCO}_{3(s)} + \text{H}_2\text{O}_{(l)} + \text{CO}_{2(g)} \rightarrow$

(iii) $\text{HCl}_{(aq)} + \text{H}_2\text{O}_{(l)} \rightarrow$

OR

During electrolysis of brine, a gas 'G' is liberated at anode. When this gas 'G' is passed through slaked lime, a compound 'C' is formed, which is used for disinfecting drinking water.

(i) Write formula of 'G' and 'C'.

(ii) State the chemical equation involved.

(iii) What is common name of compound 'C'? Give its chemical name.

The first option tests direct chemical equations from the NCERT text:

• Activity 2.4 details the reaction of zinc with sodium hydroxide to form sodium zincate and hydrogen gas.
• Section 2.1.3 details the reaction of passing excess carbon dioxide through lime water containing calcium carbonate precipitate, yielding soluble calcium hydrogencarbonate.
• Section 2.2.1 explains that $HCl$ in water produces hydronium ($H_3O^+$) and chloride ($Cl^-$) ions.

The OR option tests the industrial preparation of bleaching powder:

• Chlorine gas ($Cl_2$) is produced during the electrolysis of aqueous sodium chloride (brine).
• Passing this chlorine gas over dry slaked lime ($Ca(OH)_2$) yields calcium oxychloride ($CaOCl_2$), commonly known as bleaching powder, which is widely used as a disinfectant for drinking water.