alleryStart learning →Combining 3 mol of H2 with 2 mol of Cl2 for H2 + Cl2 giving 2HCl, which reactant limits the product?
AHydrogen, since more of it is present
BChlorine, since less of it is present
CNeither, since the ratio is already 1 to 1
DBoth equally, since each gives 2 mol HCl
Answer & Solution
Correct answer: B. Chlorine, since less of it is present
1. The balanced equation needs hydrogen and chlorine in a 1 to 1 mole ratio.
2. The mixture supplies 3 mol to 2 mol, a ratio of 1.5 to 1, which is richer in hydrogen.
3. Complete reaction of 3 mol H2 would give 6 mol HCl.
4. Complete reaction of 2 mol Cl2 would give only 4 mol HCl.
5. The smaller figure is the real yield, so chlorine limits and hydrogen is in excess.
6. Reacting all 2 mol Cl2 uses 2 mol of the 3 mol H2, leaving 1 mol H2 unreacted.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.4 Reaction Yields_
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