Question

A `10*g` mass of aluminum reacts with a `19*g` mass of oxygen gas. Which is the reagent in deficiency?

Answer 1

`2Al + 3/2O_2 rarr Al_2O_3`

Explanation:

You have done the hard part, the balanced chemical equation, the which is absolutely necessary for these sorts of reactions.

Moles of aluminum, `(10*g)/(26.98*g*mol^(-1)`; versus moles of dioxygen, `(19*g)/(32.00*g*mol^(-1)`. Given a calculator it should be easy to see the reagent in deficiency. Remember you have to account for the reaction's stoichiometry: 4 moles of aluminum require 3 moles of oxygen for reaction.