Chemistry - Balancing Equations

Question

If 10.5 g of P4 is reacted with 25.0 g of chlorine to produce phosphorus trichloride (PCl3). Write a balanced chemical reaction. Identify which of the reactant is the limiting reagent. How much phosphorus trichloride can be produced?

Answer 1

Balanced equation:

P₄ + 6Cl₂ ===> 4PCl₃

Limiting reactant: (note: there are various ways to find the limiting reactant. For me the easiest is to find moles of each, then divide that value by the coefficient in the balanced equation and the lower value is limiting.)

moles P₄ present = 10.5 g x 1 mol/123.9 g = 0.08475 moles P₄. Divide this by 1 = 0.08475

moles Cl₂ present = 25.0 g x 1 mol/70.9 g = 0.3526 moles Cl₂. Divide this by 6 = 0.0588 -> Limiting

How much PCl₃ is formed?

The amount of PCl₃ formed will be dictated by the amount of limiting reactant, Cl₂.

0.3526 moles Cl₂ x 4 moles PCl₃/6 moles Cl₂ = 0.2351 moles PCl₃ formed

0.2351 moles PCl₃ x 137 g/mole = 32.2 g PCl₃ formed