Question

1. how many moles of oxygen are needed to react with 5 moles of aluminum?

4 al + 3 o₂ → 2 al₂o₃

Explanation:

Step1: Identify mole ratio

From the balanced equation, the mole ratio of $\text{Al}$ to $\text{O}_2$ is $\frac{3\ \text{mol}\ \text{O}_2}{4\ \text{mol}\ \text{Al}}$.

Step2: Calculate moles of $\text{O}_2$

Multiply given Al moles by the ratio.
$\text{Moles of O}_2 = 7.5\ \text{mol Al} \times \frac{3\ \text{mol O}_2}{4\ \text{mol Al}}$

Step3: Compute the result

Simplify the expression.
$\text{Moles of O}_2 = \frac{7.5 \times 3}{4} = 5.625$

Answer:

5.625 moles of oxygen