Ascientist measures the mass of two liquids before and after combining them. the mass after combining the liquids is less than the sum of the masses before. where is the missing mass?

On the basis of the law of conservation of mass, the entire mass of reactants should be equivalent to the entire mass of products. However, in the given question, it is given that while measuring the mass of two liquids by the scientists, that is, before and after the reaction, it was found that the mass of the products was found less in comparison to the mass of the reactants.  

Thus, it can be concluded that the missing mass would probably be of a gas, which produced during the reaction between the two chemicals.