Read the following chemical equation.

Al + Cl2 → AlCl3

Which of the following fractions can be used for the mole ratio to determine the mass of Al from a known mass of AlCl3?

A. 2/1

B. 3/2

C. 2/2

D. 2/3

C. 2/2

Explanation:

I just took the test and got it right.; )

C. 2/2

a) Balance the chemical equation

2Al + 3Cl2 → 2AlCl3

b) We want to convert moles of AlCl3 to moles of Al

The conversion factor is either 2 mol Al/2 mol AlCl3 or 2 mol AlCl3/2 mol Al.

We choose the one that makes the units cancel:

x mol AlCl3 x (2 mol Al) / (2mol AlCl3) = x mol Al

The fraction for the molar ratio is 2/2.