Which of the following is the mass of  $\mathit{CaO}$ produced if $100\mathit{ g}$ of $\mathit{CaC}{O}_3$ is heated it produces $44\mathit{ g}$ of $C{O}_2$ and it follows the law of conversion of mass?

The mass of  $\mathit{CaO}$ produced if $100\mathit{ g}$ of $\mathit{CaC}{O}_3$ is heated it produces $44\mathit{ g}$ of $C{O}_2$ and it follows law of conversion of mass is $56\mathit{ g}$
$\mathit{CaC}{O}_3\to \mathit{ CaO }+\mathit{ C}{O}_2$
The law of conservation of mass said that, “the total mass of the reactants is equal to the total mass of the products.”
⇒Therefore, 

The total mass of the reactant = total mass of the product

⇒Here, mass of $\mathit{ CaC}{O}_3 = 100\mathit{ g}$
⇒ mass of$\mathit{ C}{O}_2 = 44\mathit{ g}$
⇒ In this reaction,

 $\mathrm{mass} \mathrm{of}\mathit{ }\mathit{CaC}{O}_3 =\mathit{ }\mathrm{Mass} \mathrm{of} C\mathit{aO }+\mathit{ }\mathrm{Mass} \mathrm{of} C{O}_2$
⇒Therefore, the $\mathrm{Mass} \mathrm{of} \mathrm{CaO} \mathrm{is}\mathit{ }= 100\mathit{ g }- 44\mathit{ g}$
                                                             $= 56\mathit{ g}$
So, if it follows the law of conversion of mass, $56\mathit{ g\; CaO}$ will be produced in this reaction.