Question

Given the unbalanced reaction of Al(s) + O2 (g) ---> Al2O3 (s), determine which reagent, and how much will be left over after the reaction of 5.0 mol of Al (s) with 4.0 mol of O2 (g).

Answer 1

Balanced equation 4Al+3O2----------> 2Al2O3

Here, 4 moles of aluminum require 3moles of oxygen to make a 2moles of Al2O3.

4moles of Al -------- 3 moles of O2

5moles of Al ----------? moles of O2

Moles of O2 = (5*3)/4 = 3.75 moles of O2

But given moles of O2 is 4

Left over reagent is oxygen O2.

0.5 moles or 16grams of O2 is leftover.