Which of the following is the mass of $\mathrm{HCl}$ required if $1.06 \mathrm{g}$ of ${\mathrm{Na}}_2{\mathrm{CO}}_3$ completely reacts with $\mathrm{HCl}$ to produce $1.17 \mathrm{g}$ $\mathrm{NaCl}$ and $0.62 \mathrm{g}$ of ${\text{H}}_{2}C{O}_3$ and the reaction follows the law of conservation of mass?

The mass of $\mathit{HCl}$ required if $1.06 \mathrm{g}$ of ${\mathit{Na}}_{2}C{O}_3$ completely reacts with $\mathit{HCl}$ to produce $1.17 \mathrm{g}$ $\mathit{NaCl}$ and $0.62 \mathrm{g}$ of $H_{2}C{O}_3$ and the reaction follows the law of conservation of mass is $0.73 \mathrm{g}$

The chemical reaction is, ${\mathit{Na}}_{2}C{O}_3+ 2\mathit{HCl }\to \mathit{ }2\mathit{NaCl }+ H_{2}C{O}_3$

Here, ${\mathit{Na}}_{2}C{O}_3$ and $\mathit{HCl}$ are the reactants.
$\mathit{NaCl }$ and $H_{2}C{O}_3$ are the products.

The law of conservation of mass said that, “the total mass of the reactants is equal to the total mass of the products.”
Therefore,

$\mathrm{The} \mathrm{total} \mathrm{mass} \mathrm{of} \mathrm{the} \mathrm{reactants} = \mathrm{Total} \mathrm{mass} \mathrm{of} \mathrm{the} \mathrm{products}.$
Or, $\mathrm{Mass} \mathrm{of} {\mathrm{Na}}_2{\mathrm{CO}}_3\mathrm{ }+ \mathrm{Mass} \mathrm{of} \mathrm{HCl} \mathrm{ }= \mathrm{Mass} \mathrm{of} \mathrm{NaCl} + \mathrm{Mass} \mathrm{of} {\mathrm{H}}_2{\mathrm{CO}}_3$
Or, $1.06 \mathrm{g} + \mathrm{Mass} \mathrm{of} \mathrm{HCl} \mathrm{ }=\mathrm{ }1.17 \mathrm{g} +\mathrm{ }0.62 \mathrm{g}$
 

So, $\mathrm{Mass} \mathrm{of} \mathrm{HCl} \mathrm{is} =\mathrm{ }1.17 \mathrm{g} +\mathrm{ }0.62 \mathrm{g} -\mathrm{ }1.06 \mathrm{g}$
                                     $=\mathrm{ }0.73 \mathrm{g}$
Therefore, $0.73 \mathrm{g}$ of $\mathit{HCl}$ is required to complete the above reaction.