A 12.00g sample of MgCl2 was dissolved in water. The solution was then treated with 0.2500mol of AgNO3 to precipitate all the chloride ions from the solution. Calculate the purity (as a mass percentage) of MgCl2 in the sample?

The percentage purity of magnesium chloride in the sample is 96.04 %

Explanation:

The chemical equation for the reaction of silver nitrate and magnesium chloride follows:

By Stoichiometry of the reaction:

2 moles of silver nitrate reacts with 1 mole of magnesium chloride

So, 0.2500 moles of silver nitrate will react with = of magnesium chloride

To calculate the mass for given number of moles, we use the equation:

Moles of magnesium chloride = 0.125 moles

Molar mass of magnesium chloride = 92.2 g/mol

Putting values in above equation, we get:

To calculate the percentage purity of sample, we use the equation:

Mass of pure magnesium chloride = 11.525 grams

Mass of impure magnesium chloride = 12.00 grams

Putting values in above equation, we get:

Hence, the percentage purity of magnesium chloride in the sample is 96.04 %