1. Liquid phosphorus trichloride, PCl3 is made by the direct combination of phosphorus and chlorine.

a. What is the maximum mass of PCl3 that can be produced from 125 g of P4 and 323 g Cl2?
b. What mass of P4 remains after the reaction?

1 answer

balance the equation
P4 + 6Cl2 >>> 4PCl3

moles P4= 125/30.9 about 4
moles Cl2= 323/70 about 4.5

we need six moles Cl2 for each mole of P4, so we have an excess of P4.
max moles P4 used: 323/(70*6)
then convert that to mass

mass remaining=125-max used