1 g of a mixture of ${\mathrm{Na}}_2{\mathrm{CO}}_3$ and ${\mathrm{NaHCO}}_3$ is heated at ${270}^{\circ }\mathrm{C}$. The volume of ${\mathrm{CO}}_2$ produced at STP is 112 mL. The % of ${\mathrm{NaHCO}}_3$ in the mixture is _________

${\mathrm{NaHCO}}_3$ decomposes at ${270}^{\circ }\mathrm{C}$ but the decomposition temperature of ${\mathrm{Na}}_2{\mathrm{CO}}_3$ is very

$\underset{2\times 84\mathrm{g}}{2\mathrm{Na}H{\mathrm{CO}}_3}\stackrel{{270}^{\circ }\mathrm{C}}{⟶}{\mathrm{Na}}_2{\mathrm{CO}}_3+\underset{22.4\mathrm{L}}{{\mathrm{CO}}_2}+{\mathrm{H}}_2\mathrm{O}$

$\begin{array}{rr} & 22.4\mathrm{L}\text{ of }{\mathrm{CO}}_2\text{ produced by }=2\times 84g {\mathrm{NaHCO}}_3\end{array}$

$0.112\mathrm{L}$ of ${\mathrm{CO}}_2$ produced by $=\frac{2\times 84}{22.4}\times 0.112$

$1\mathrm{g}$ of mixture contains $=0.84\mathrm{g}{\mathrm{NaHCO}}_3$

% of ${\mathrm{NaHCO}}_3=84\mathrm{\%}$