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?

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Answer 1 · 2016-05-12T13:24:56

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

#1/4P_4 +5/2Cl_2 rarr PCl_5#

This is of course a redox reaction, and establishes the stoichiometry. One equiv of phosphorus is oxidized by #5/2# equiv of chlorine gas.

#"Moles of phosphorus ATOMS"# #=# #(23.0*g)/(31.00*g*mol^-1)# #=# #0.742*mol#.

#"Moles of chlorine ATOMS"# #=# #(160.0*g)/(35.45*g*mol^-1)# #=# #4.51*mol#.

Clearly, phosphorus is in deficiency, and 100% yield would give rise to #0.742*mol# #PCl_5# (which of course contains #3.71# #mol# chlorine.