Chemistry Stoich

Question

How many moles of As₂O₅ are produced when 5.62 mol of As react with 7.50 mol of O₂?

As (s) +  O₂ (g)  ⟶   As₂O₅ (s) 

Answer 1

The first thing we must do is to BALANCE the equation:

4As (s) +  5O₂ (g)  ⟶   2As₂O₅ (s)  .. balanced equation

Find limiting reactant. Divide moles of each reactant by the corresponding coefficient in the balanced equation. Whichever value is less, represents the limiting reactant.

For As: 5.62 mol ÷ 4 = 1.4

For O₂: 7.50 mol ÷ 5 = 1.5

Since 1.4 is less than 1.5, As is the limiting reactant. Next, we use the moles of the limiting reactant (5.62), and the stoichiometry of the balanced equation to find the moles of As₂O₅ produced:

5.62 mol As x 2 mol As₂O₅ / 4 mol As = 2.81 mol As₂O₅