Question

Aluminium does not react with water at room temperature because:
A.) It is above hydrogen in the activity series
B.) It is below hydrogen in the activity series
C.) It is with a thin film of $AlN$
D.) It is covered with thin film of $A{l_2}{O_3}$.

Answer 1

To solve this question, we need to know that aluminium can react with water but at high temperature and at room temperature a layer of oxide is formed over aluminium which resists the reaction to take place.

Complete step by step answer:
Aluminium reacts differently with water at different temperatures and gives the different and most stable product at different temperatures.
When temperature is below equal or below the room temperature then aluminium metal rapidly develops a thin layer of aluminium oxide of a few millimeters that prevents aluminium from reacting with water and thus inhibits the reaction.
When the temperature is from room temperature to $280^\circ C$ , then $Al{(OH)_2}$ is the most stable product. Its reaction can be shown as:
$2Al + 6{H_2}O \to 2Al{(OH)_3} + 3{H_2}$
When the temperature is from $280 - 480^\circ C$, then $AlO(OH)$ is the most stable product. This reaction can be shown as:
$2Al + 4{H_2}O \to 2AlO(OH) + 2{H_2}$
When the temperature is above $480^\circ C$, then $A{l_2}{O_3}$ is the most stable product. This reaction can be shown as:
$2Al + 3{H_2}O \to A{l_2}{O_3} + 3{H_2}$
In all these reactions hydrogen is released as the byproduct and also all these reactions are exothermic, that is heat is released in these reactions.
Hence, we can say that at room temperature aluminium does not react with water because aluminium is covered with thin film of aluminium oxide($A{l_2}{O_3}$).
Hence, option D is the correct answer.

Note:
We need to remember that reactions of aluminium with water are thermodynamically favorable from room temperature past the melting point of aluminium that is $660^\circ C$. But at room temperature or below room temperature aluminium does not react with water.