Are the following data sets on chemical changes consistent with the law of conservation of mass?

(a) A 15.0 g sample of sodium completely reacts with 19.6 g of chlorine to form 34.6 g of sodium chloride.

the answer is yes, because 15 and 19.6 add up to 34.6 right?

1 answer

ok.. sorry to post anyother question on here but i got the answer to my previous question but im having trouble with this one..

In the explosion of a hydrogen-filled balloon, 0.43 g of hydrogen reacted with 7.2 g of oxygen to form how many grams of water vapor? (Water vapor is the only product.)

ive tried dividing them both ways and adding and multiplying but i can't get the right answer.

I have no idea how to do it. can anyone help me?