If the total mass of the products of a reaction is

250 g, what was the total mass of the reactants

Due to the law of conservation of mass, which states that nothing is lost and nothing is gained but only transformed. A number of reactants is equal to a number of products. if the mass of products is 250g the total mass of reactants will be 250g.

Every chemical equation must be balanced to preform the conservation of mass law, so, what ever is on the products is going to be on the reactants. The mass is not created nor destroyed.

Answer: 250 g