Use the Conservation of Mass Interactive to answer the question

Question

Consider the reaction.

If the small amount of  is combined with the small amount of  what is the mass of the products? The mass of any excess reactants will also be included in this total.

Answer 1

Is this some sort of interactive virtual lab question? It refers to "the small amount" for both substances, but doesn't give any numbers - there isn't anything to calculate. The answer is that the mass of the reactants will always be equal to the mass of the products plus any excess (unreacted) reactants.

This is the Law of Conservation of Mass. Basically it says that matter cannot appear from nowhere or disappear into nothingness. If you start with 27.4 g of stuff, you will end up with 27.4 g of stuff, but it may (or may not) have changed chemical identity. I think that's what they are trying to show you in this situation.

For example, if I mix 5 g of dirt with 10 g of water I will get 15 grams of mud. That's just making a mixture, with no chemical changes involved. But if I mix 20 g MnS with 20 g HCl, I will end up with 40 g of total stuff - some will be MnCl2, some will be H2S, which are new substances produced in the chemical reaction (reaction products). But there will also likely be some unreacted MnS and/or HCl. These reactants aren't always present in the right ratios to fully react with each other with no "leftovers" of something. In the example I set up, I know they aren't going to fully react with each other with no leftovers of something. This would be where you explore the concept of a "Limiting Reactant", but this question doesn't dig that deep...

I don't think anyone can answer the question "What is the mass of the products?" (including unreacted reactants), because we don't know the masses of the reactants. But we could say the answer is "the same as the total mass of reactants" even if we don't know the numbers! Hope that helps, good luck!