Question

(b) Choose the most appropriate answer from the following list of oxides which fit the description. Each answer may be used only once.

$[{\mathrm{SO}}_2,{\mathrm{SiO}}_2,{\mathrm{Al}}_2{\mathrm{O}}_3,\mathrm{MgO},\mathrm{CO},{\mathrm{Na}}_2\mathrm{O}]$.
(i) A basic oxide.
(ii) An oxide which dissolves in water forming an acid.
(iii) An amphoteric oxide.
(iv) A covalent oxide of a metalloid.

Answer 1

Part 1: Basic Oxide:-

1. Metals form basic oxides while non-metals form acidic oxides.
2. When we move from left to right in a period, the formation of acidic oxide increases and that of basic oxide decreases.
3. Hence ${\mathrm{Na}}_2\mathrm{O}$ is the strongest basic oxide.
4. MgO is also a basic oxide.

Part 2: An oxide which dissolves in water forming an acid:-

1. ${\mathrm{SO}}_2$ dissolves in water and forms an acid (sulfurous acid) upon reaction.

Part 3: Amphoteric oxide:-

1. ${\mathrm{Al}}_2{\mathrm{O}}_3$ is an amphoteric oxide.
2. This is because it reacts with both acid and bases in order to produce salts and hydrogen gas.

Part 4: A covalent oxide of a metalloid:-

1. Silicon is a metalloid.
2. Hence ${\mathrm{SiO}}_2$is a covalent oxide of metalloid

Final answer:-

(i) A basic oxide- ${\mathrm{Na}}_2\mathrm{O}$
(ii) An oxide which dissolves in water forming an acid- ${\mathrm{SO}}_2$
(iii) An amphoteric oxide- ${\mathrm{Al}}_2{\mathrm{O}}_3$
(iv) A covalent oxide of a metalloid - ${\mathrm{SiO}}_2$