Question

defination of law of mass??

Answer 1

Rate of a chemical reaction is proportional to the concentrations of the reacting substances.
or
mass can neither be created nor be destroyed!!
or the amt of reactants used in a reaction will be equal to da mass of the product after da reaction!!

=D

Answer 2

The law stating that the rate of any given chemical reaction is proportional to the product of the activities (or concentrations) of the reactant