Question

Sodium hydrogen carbonate, when added to acetic acid, evolves gas. Which of the following statements are true about the gas evolved? $\left(\mathrm{i}\right)$ It turns lime water milky $\left(\mathrm{ii}\right)$ It extinguishes a burning splinter $\left(\mathrm{iii}\right)$ It dissolves in a solution of sodium hydroxide $\left(\mathrm{iv}\right)$ It has a pungent odor.

• A. $\left(\mathrm{i}\right)$ and $\left(\mathrm{ii}\right)$
• B. $\left(\mathrm{i}\right),\left(\mathrm{ii}\right)$ and $\left(\mathrm{iii}\right)$
• C. $\left(\mathrm{ii}\right),\left(\mathrm{iii}\right)$ and $\left(\mathrm{iv}\right)$
• D. $\left(\mathrm{i}\right)$ and $\left(\mathrm{iv}\right)$

Answer 1

The correct option is A

$\left(\mathrm{i}\right)$ and $\left(\mathrm{ii}\right)$

The explanation for the correct option:

Option (A): $\left(\mathrm{i}\right)$ and $\left(\mathrm{ii}\right)$

1. An acid reacts with a base to produce salt and water in a neutralization reaction.
2. When Sodium Hydrogen carbonate and acetic acid mix, carbon dioxide gas is produced, as well as sodium ethanoate.$\underset{\mathrm{Sodium}\mathrm{hydrogencarbonate}}{{\mathrm{NaHCO}}_3\left(\mathrm{s}\right)}+\underset{\mathrm{Acetic}\mathrm{acid}}{{\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{l}\right)}\to \underset{\mathrm{Sodium}\mathrm{ethanoate}}{{\mathrm{CH}}_3\mathrm{COONa}\left(\mathrm{s}\right)}+\underset{\mathrm{water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}$
3. The gas produced is carbon dioxide, which is a colorless and odorless gas.
4. When carbon dioxide is passed through lime water it turns it to milky because of the formation of Calcium carbonate. $\underset{\mathrm{Calcium}\mathrm{hydroxide}}{\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{l}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Cacium}\mathrm{carbonate}}{{\mathrm{CaCO}}_3\left(\mathrm{s}\right)}+\underset{\mathrm{water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$
5. Also, carbon dioxide extinguishes a burning splinter because it does not support combustion.

Hence, Option (A) is the correct option.