# The reaction of chlorine gas with solid phosphorus (P_4) produces solid phosphorus pentachloride. When 160 of chlorine reacts with 23.0 g of P_4, which reactant is limiting? Which reactant is in excess?

May 12, 2016

We need a balanced chemical equation, before we determine the reagent in excess. I think it is chlorine gas.

#### Explanation:

$\frac{1}{4} {P}_{4} + \frac{5}{2} C {l}_{2} \rightarrow P C {l}_{5}$

This is of course a redox reaction, and establishes the stoichiometry. One equiv of phosphorus is oxidized by $\frac{5}{2}$ equiv of chlorine gas.

$\text{Moles of phosphorus ATOMS}$ $=$ $\frac{23.0 \cdot g}{31.00 \cdot g \cdot m o {l}^{-} 1}$ $=$ $0.742 \cdot m o l$.

$\text{Moles of chlorine ATOMS}$ $=$ $\frac{160.0 \cdot g}{35.45 \cdot g \cdot m o {l}^{-} 1}$ $=$ $4.51 \cdot m o l$.

Clearly, phosphorus is in deficiency, and 100% yield would give rise to $0.742 \cdot m o l$ $P C {l}_{5}$ (which of course contains $3.71$ $m o l$ chlorine.