Does this equation follow the laws of conservation of mass? why? CuO(s) + H2(g) = Cu(s) + H2O(g)

(twos are subscript_)

Yes

Explanation:

Chemical equation:

CuO  + H₂    →      Cu + H₂O

Law of conservation of mass:

According to the law of conservation mass, mass can neither be created nor destroyed in a chemical equation.

This law was given by French chemist  Antoine Lavoisier in 1789. According to this law mass of reactant and mass of product must be equal, because masses are not created or destroyed in a chemical reaction.

For example:

In given reaction:

CuO  + H₂    →      Cu + H₂O

there are 1 copper atoms, one oxygen atoms and two hydrogen atoms on the both side of equation so this reaction followed the law of conservation of mass.