Question

Solid molecular phosphorus reacts with chlorine gas to form phosphorus trichloride according to the chemical equation shown below. If only 6.8 g of PCl3 is produced when 5.0 g of P4 and 7.5 g of Cl2 are combined, what is the percent yield of the reaction?

P4 (s) + 6Cl2 (g) → 4PCl3 (l)

Answer 1

Balanced equation:
P₄(s) + 6 Cl₂(g) ====> 4 PCl₃(l)
Reaction type: synthesis

Molar mass of P4 = 123.89 gm/mol

Molar mass of Cl2 = 70.91 gm/mol

Molar mass of PCl3 = 137.33 gm/mol

5.0 g of P4 = 5 gm / 123.89 gm/mol = 0.04035 Moles

7.5 g of Cl2 = 7.5 gm / 70.91 gm/mol =  0.10577 Moles

Here Cl₂ is limiting reagent

Moles of PCl3 obtained =  0.07051 Moles

Theoretical mass of PCl3 obtained = 0.07051 x 137.33 = 9.684 gm

Percentage yield of the reaction = 6.8 x 100 % / 9.684 = 70.21 %