04.05 mol
The reaction of chlorine gas with solid phosphorus (P4) produces solid
phosphorus pentachloride. When 32.0 g of chlorine reacts with 46.0 g of P4.
What is the mass in excess of the excess reactantt?

34.8 g

Explanation:

We have the masses of two reactants, so this is a limiting reactant problem.

We will need a balanced equation with masses, moles, and molar masses of the compounds involved.

1. Gather all the information in one place with molar masses above the formulas and masses below them.  

Mᵣ:         123.90    70.91      208.24

                 P₄   +   20Cl₂ ⟶ 4PCl₅

Mass/g:   46.0       32.0

2. Calculate the moles of each reactant  

3. Calculate the moles of PCl₅ we can obtain from each reactant

From P₄:

The molar ratio is 4 mol PCl₅:4 mol P₄

From Cl₂:

The molar ratio is 4 mol PCl₅:20 mol Cl₂

4. Identify the limiting and excess reactants

The limiting reactant is chlorine, because it gives the smaller amount of PCl₅.

The excess reactant is phosphorus.

5. Mass of excess reactant

(a) Moles of P₄ reacted

The molar ratio is 1 mol P₄:20 mol Cl₂

(b) Mass of P₄ reacted

(c) Mass of P₄ remaining

Mass remaining = original mass – mass reacted = (46.0 - 11.18) g = 34.8 g P₄