Calculate the volume of chlorine required for complete (up to PCl5) and incomplete (up to PCL3)

Calculate the volume of chlorine required for complete (up to PCl5) and incomplete (up to PCL3) combustion of a 1.55 g sample of phosphorus.

Given:
m (P) = 1.55 g

To find:
V1 (Cl2) -?
V2 (Cl2) -?

1) 2P + 5Cl2 => 2PCl5;
2) n (P) = m / M = 1.55 / 31 = 0.05 mol;
3) n1 (Cl2) = n (P) * 5/2 = 0.05 * 5/2 = 0.125 mol;
4) V1 (Cl2) = n1 * Vm = 0.125 * 22.4 = 2.8 l;
5) 2P + 3Cl2 => 2PCl3
6) n (P) = m / M = 1.55 / 31 = 0.05 mol;
7) n2 (Cl2) = n (P) * 3/2 = 0.05 * 3/2 = 0.075 mol;
8) V2 (Cl2) = n2 * Vm = 0.075 * 22.4 = 1.68 liters.

Answer: The volume of Cl2 is 2.8L and 1.68L.