Question

How many moles of chloride ions are in 0.2550 g of aluminum chloride using AlCl3 's molar mass of 133.34 g / mol:?

Answer 1

I got 0.001912 using dimensional analysis. See the picture for work.

Answer 2

Explanation:

It is known that number of moles is the amount of mass present in a given molar mass of the substance.

Mathematically,   No. of moles = $\frac{mass}{\text{molar mass}}$

We are given that mass of $AlCl_{3}$ is 0.255 g and molar mass of $AlCl_{3}$ is 133.34 g/mol.

Therefore, number of moles of $AlCl_{3}$ is calculated as follows.

        No. of moles = $\frac{mass}{\text{molar mass}}$

                              = $\frac{0.255 g}{133.34 g/mol}$  

                              = $1.912 \times 10^{-3}$ mol

Since, there are three chlorine atoms present in one mole of $AlCl_{3}$. Therefore, moles of chlorine ions present in given 0.255 g will be calculated as follows.

             $3 \times 1.912 \times 10^{-3}$ mol

            = $5.736 \times 10^{-3} mol$

Thus, we can conclude that $5.736 \times 10^{-3} mol$ chloride ions are in 0.2550 g of aluminum chloride using $AlCl_{3}$'s molar mass of 133.34 g/mol.