Just follow the example problem on the link.
http://www.jiskha.com/science/chemistry/stoichiometry.html
Zinc metal reacts with hydrochloric acid to produce hydrogen gas according to the equation below. What volume of hydrogen at STP is released when 15.1 grams of zinc react at STP?
Zn(s) + 2HCl(aq) �¨ ZnCl2(aq) + H2(g)
2 answers
A) HCL B)1.35G