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) + 2"HCl"(aq) -> "MgCl"_2(aq) + "H"_2(g)

1 Answer
Bio
May 7, 2016

2.24 "L"

Explanation:

Step 1: determine the reaction

The chemical equation is already given.

"Mg" + 2 "HCl" -> "MgCl"_2 + "H"_2

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 0.100 "mol" of "Mg" will react with 0.100 "mol" xx 2 = 0.200 "mol" of "HCl". This leaves 0.500 "mol" - 0.200 "mol" = 0.300 "mol" of "HCl".

Step 3: determine how much "H"_2 is produced.

0.100 "mol" of "Mg" and 0.200 "mol" of "HCl" will produce 0.100 "mol" of "H"_2.

Step 4: determine the volume at STP

Each mole of ideal gas occupies 22.4 "L" at STP. Therefore, 0.100 "mol" of "H"_2 will occupy 2.24 "L" of space.

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