Question

Hydrogen and chlorine react to yield hydrogen chloride: H2+ Cl2 ( 2HCl. How many grams of HCl are formed from reaction of 3.56 g of H2 with 8.94 g of Cl2? Which reactant is limiting?

Answer 1

I do limiting reagent problems the long way. There are shorter ways to work this problem but I think they are more difficult to explain.

H2 + Cl2 ==> 2HCl

mols H2 = grams/molar mass = 3.56/2 = 1.78
mols Cl2 = 8.94/71 = 0.126

Using the coefficients in the balanced equation, we now convert each to mols HCl produced if we had all of the other compound we needed.
1.78 mols H2 x (2 mol HCl/1 mol H2) = 1.78 x 2/1 = 3.56 mol HCl.

0.126 mols Cl2 x (2 mol HCl/1 mol Cl2) = 0.126 x 2/1 = 0.252 mol HCl.

The two values HCl produced do not agree; in limiting reagent problems the correct value is ALWAYS the smaller value; therefore, Cl2 is the limiting reagent and 0.252 mol HCl will be produced.

Convert mols HCl to g HCl.
grams = mols x molar mass = ?

Answer 2

9.2g HCl