Question

A student would like to use gravimetric analysis to determine the percent by mass of magnesium chloride in a contaminated mixture containing magnesium chloride.
Which of the following compounds would be the BEST substance to react the contaminated mixture with to determine the mass percent?

• A. silver nitrate.
• B. Potassium chloride.
• C. Sodium acetate.
• D. Lithium sulfate.

Answer 1

The correct option is A silver nitrate.

The student needs to form a precipitate that they can weigh to determine the amount of magnesium or chlorine in the contaminated sample. Knowledge of the solubility rules is necessary for this question. Group 1 elements, nitrates, and acetates always form soluble compounds. Halogens are usually soluble except with silver, lead and mercury. Silver nitrate will be the only substance to form a precipitate. Magnesium chloride and silver nitrate will react to form a silver chloride precipitate.