Question

When sodium reacts with cold water, then the product formed will be :
a.) $N{a_2}O$
b.) $NaOH$
c.) $N{a_2}C{O_3}$
d.) All of these

Answer 1

Hint: The sodium metal belongs to group 1 and can easily donate its one valence electron to achieve noble gas configuration. Thus, it will act as a positive species. The water molecule consists of ${H^ + }$and $O{H^ - }$ions which are as-
${H_2}O \rightleftharpoons {H^ + } + O{H^ - }$
The negative end of water combines with positive Sodium ions producing the product which is an ionic compound.

Complete step by step solution:
As we know that sodium belongs to group 1 alkali metals. These metals have one valence electron and donating it, they are in a noble gas state which is highly stable. So, even the sodium like its other family members is always eager to donate this electron to achieve a noble gas configuration. This is the reason the sodium is very reactive in nature.
When the sodium is burnt in air, as the air contains oxygen. So, it reacts with oxygen in air to form the sodium peroxide and sodium oxide. The reaction for this can be written as-
$2Na(s) + {O_2} \to 2N{a_2}{O_2}(s)$
$4Na(s) + {O_2} \to 2N{a_2}O(s)$
The sodium reacts with water very easily.
It reacts with water to give a solution of sodium hydroxide and hydrogen gas with a large amount of heat. The reaction is highly exothermic in nature. The hydrogen gas being vapour in nature is evolved out easily and the resultant is the solution of sodium hydroxide.
The reaction with water is as-
$2Na(s) + 2{H_2}O \to 2NaOH(aq) + {H_2}(g)$
The solution is colourless and basic in nature.
Thus, the product formed after the reaction of sodium metal with water is sodium hydroxide.

So, the option b.) is the correct answer.

Note: It must be noted that the reaction of sodium with water is exothermic in nature. Sometimes, during the reaction, the sodium may become so hot that it can catch fire. The metal shows orange colour when it burns.