Question

A student takes about $2\mathrm{mL}$ ethanoic acid in a dry test tube and adds a pinch of sodium hydrogen carbonate to it. He reports the following observations:

(I) immediately a colorless and odorless gas evolves with brisk effervescence.

(II) The gas turns lime water milky when passes through it.

(III) The gas burns with an explosion when a burning splinter is brought near it.

(IV) The gas extinguishes the burning splinter that is brought near it.

• A. I, II, and III
• B. II, III, and IV
• C. III, IV, and V
• D. I, II, and IV

Answer 1

The correct option is D

I, II, and IV

A functional group is defined as a group of atoms that exist in a molecule and describes the characteristics reactions of organic compounds is called a functional group.

The functional group present in carboxylic acid is $\mathrm{COOH}$.

In the experiment, $2\mathrm{mL}$ Ethanoic acid (${\mathrm{CH}}_3\mathrm{COOH}$) is poured into a dry test tube and a pinch of Sodium hydrogen carbonate (${\mathrm{NaHCO}}_3$) in solid form is added to the reaction mixture. It reacts with Ethanoic acid (${\mathrm{CH}}_3\mathrm{COOH}$) to form Carbon dioxide (${\mathrm{CO}}_2$), Sodium acetate (${\mathrm{CH}}_3\mathrm{COONa}$), and water (${\mathrm{H}}_2\mathrm{O}$) as the final product.

The reaction that happens in the test tube is written as follows:

$$\begin{gathered} {\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{l}\right)+{\mathrm{NaHCO}}_3\left(\mathrm{s}\right)\to {\mathrm{CH}}_3\mathrm{COONa}\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ (\mathrm{Ethanoic}(\mathrm{sodium}\mathrm{hydrogen}(\mathrm{sodium}(\mathrm{carbon}+\left(\mathrm{water}\right) \\ \mathrm{acid})\mathrm{carbonate})\mathrm{acetate})\mathrm{dioxide}) \end{gathered}$$

The following observations can be made:

1. The student observes that Carbon dioxide gas is evolved immediately with brisk effervescence. It is an odorless and colorless gas.
2. Carbon dioxide turns lime water milky when carbon dioxide is passed through it.
3. Carbon dioxide is a non-supporter of ignition, So the carbon dioxide gas extinguishes the burning splinter that is brought near it.

Hence, option (D) is the correct option.