Question

What is the law of conservation of mass?

Answer 1

• According to the Law of Conservation of mass - ‘mass (matter) can neither be created nor destroyed in a chemical reaction’.
• So, the total mass of all the elements present in the products of a chemical reaction should be equal to the total mass of all the elements present
  in the reactants.
• In other words, the number of atoms of each element in the products must be equal to the number of atoms of these elements in the reactants.
• For example - $\mathrm{C}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)$

Elements	Number of atoms on reactant side	Number of atoms on product side
C	1	1
O	2	2

Since, the number of atoms of each reactant is equal to that of the product. Hence, the reaction is in accordance with the Law of Conservation of Mass.