Question

question 12 (5 points)
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whats the empirical formula of a compound composed of 22.55% p and 77.45% cl?
a) pcl₅
b) pcl₂
c) pcl₄
d) pcl₃

Explanation:

Step1: Assume 100g of the compound

We assume we have 100g of the compound, so we have 22.55g of P and 77.45g of Cl.

Step2: Calculate moles of P

Molar mass of P is 30.97 g/mol. Moles of P = $\frac{22.55\mathrm{g}}{30.97\mathrm{g/mol}} \approx 0.728\mathrm{mol}$

Step3: Calculate moles of Cl

Molar mass of Cl is 35.45 g/mol. Moles of Cl = $\frac{77.45\mathrm{g}}{35.45\mathrm{g/mol}} \approx 2.185\mathrm{mol}$

Step4: Find the mole ratio

Divide moles of each by the smallest number of moles (0.728 mol for P).
Ratio of P: $\frac{0.728}{0.728} = 1$
Ratio of Cl: $\frac{2.185}{0.728} \approx 3$
So the empirical formula is $PCl_3$.

Answer:

D) $PCl_3$