Chemistry

Chemistry

Problem

For the reaction 2A(g)+B(g)→3C(g)2\text{A}(g)+\text{B}(g)\rightarrow 3\text{C}(g), the enthalpy change is ΔH=−250 kJ\Delta H = -250\,\text{kJ} for the reaction as written. A mixture contains 3.0 mol3.0\,\text{mol} of A and 4.0 mol4.0\,\text{mol} of B. Which reactant limits the amount of heat qq that will be released when the reaction proceeds to completion?
Intuitive explanation

This problem asks you to connect stoichiometry with thermochemistry. The key insight is that ΔH=−250 kJ\Delta H = -250\,\text{kJ} applies to the specific mole ratios in the balanced equation—so whichever reactant runs out first will determine how far the reaction actually goes and thus how much heat is released. Find the limiting reactant using the stoichiometric ratio, and that's your answer.

Intuitive explanation

This problem asks you to connect stoichiometry with thermochemistry. The key insight is that ΔH=−250 kJ\Delta H = -250\,\text{kJ} applies to the specific mole ratios in the balanced equation—so whichever reactant runs out first will determine how far the reaction actually goes and thus how much heat is released. Find the limiting reactant using the stoichiometric ratio, and that's your answer.

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