Question

how many moles of bromine are needed to create 5.0 moles of phosphorus tribromide?\\(2p + 3br_2 \
ightarrow 2pbr_3\\)\\(\bigcirc\\) 7.5 mol\\(\bigcirc\\) 15.0 mol\\(\bigcirc\\) 3.3 mol\\(\bigcirc\\) 2.5 mol

Explanation:

Step1: Identify mole ratio

From reaction: $\frac{n(\text{Br}_2)}{n(\text{PBr}_3)} = \frac{3}{2}$

Step2: Solve for $n(\text{Br}_2)$

$n(\text{Br}_2) = \frac{3}{2} \times n(\text{PBr}_3)$
Substitute $n(\text{PBr}_3)=5.0\ \text{mol}$:
$n(\text{Br}_2) = \frac{3}{2} \times 5.0\ \text{mol} = 7.5\ \text{mol}$

Answer:

7.5 mol