Question

Sodium bicarbonate on heating decomposes to form sodium carbonate, $C{O_2}$ and water. If $0.2$ mole of sodium bicarbonate is completely decomposed, how many moles of sodium carbonate is formed?
A. $0.1$
B. $0.2$
C. $0.05$
D. $0.025$

Answer 1

The sodium bicarbonate on heating decomposes to sodium carbonate, carbon dioxide and water. We need to balance the equation and apply stoichiometry laws.

Complete step by step answer: $2NaHC{O_3}(S)\xrightarrow{\Delta }N{a_2}C{O_3}\left( S \right) + C{O_2}\left( g \right) + {H_2}O\left( g \right)$
This equation shows that sodium bicarbonate on heating decomposes to form sodium carbonate, $C{O_2}$ and water. Taking in view the stoichiometry laws, we can say that,
$2$moles of sodium bicarbonate decomposes to form $1$ mole of sodium carbonate, $1$ mole of carbon dioxide and $1$ mole of water.
According to the question we only need the moles of sodium bicarbonate and sodium carbonate. So, writing both is:
$2$ moles of sodium bicarbonate give $1$ mole of sodium carbonate.
$1$ mole of sodium bicarbonate give $0.5$ moles of sodium carbonate
$0.2$ moles of sodium bicarbonate give $0.1$ mole of sodium carbonate
So, the answer is (A) $0.1$ mole of $N{a_2}C{O_3}$

Additional Information: Like most of the chemical reactions, the rate of the reaction depends upon temperature. When dry, baking soda doesn’t decompose very quickly, although it does have a shelf life. So, you should test it before using it as an ingredient or in an experiment.
$2NaHC{O_3}(S)\xrightarrow{\Delta }N{a_2}C{O_3}\left( S \right) + C{O_2}\left( g \right) + {H_2}O\left( g \right)$
Sodium carbonate or washing soda also undergoes a decomposition reaction although this molecule is more heat stable than sodium bicarbonate. The balanced equation for the reaction is:
$N{a_2}C{O_3}\left( S \right) \to N{a_2}O\left( S \right) + C{O_2}\left( g \right)$
The decomposition reaction of sodium carbonate (anhydrous) into sodium oxide and carbon dioxide occurs slowly at room temperature and proceeds to completion at $851^{o}C\,(1124K)$

Note: Sodium carbonate is a stronger base compound and is diprotic. It can convert into sodium bicarbonate after it reacts to acid. Meanwhile, sodium bicarbonate is monoprotic and a weak base. Both compounds are widely used and applied.