Magnesium metal (0.100 mol) and a volume of aqueous hydrochloric acid that contains 0.500 mol of HCl are combined and react to completion. How many liters of hydrogen gas, measured at STP, can be produced? Mg(s)+2HCl(aq)MgCl2(aq)+H2(g)

1 Answer
May 7, 2016

2.24L

Explanation:

Step 1: determine the reaction

The chemical equation is already given.

Mg+2HClMgCl2+H2

Step 2: determine which reactant is limiting

0.100 mol of Mg reacts with 0.500 mol of HCl, which of them will run out first?

From the reaction, the ratio of Mg to HCl used is 1:2. This means that if the reaction goes to completion, the 0.100mol of Mg will react with 0.100mol×2=0.200mol of HCl. This leaves 0.500mol0.200mol=0.300mol of HCl.

Step 3: determine how much H2 is produced.

0.100mol of Mg and 0.200mol of HCl will produce 0.100mol of H2.

Step 4: determine the volume at STP

Each mole of ideal gas occupies 22.4L at STP. Therefore, 0.100mol of H2 will occupy 2.24L of space.