Determine the amount of potassium chloride in each solution.

Question

40 mg of a solution containing 14 % KCl by mass

24.2 kg of a solution containing 20.7 % KCl by mass

Express your answer using three significant figures.

Answer 1

40 mg of a solution containing 14% KCl by mass

• 14% by mass = 14 g KCl/100 g solution = 0.14 g KCl/g solution
• 40 mg solution x 1 g/1000 mg = 0.04 g solution
• 0.04 g solution x 0.14 g KCl/g solution = 0.0056 g KCl = 5.60 mg KCl (expressing to 3 significant figures is incorrect since 40 mg has only 1 significant figure)

 

24.2 kg of a solution containing 20.7% KCl by mass

• 20.7% by mass = 20.7 g KCl/100 g solution = 0.207 g KCl/g solution
• 24.2 kg solution x 1000 g/kg = 24,200 g solution
• 24,200 g solution x 0.207 g KCl/g solution = 5,009.4 g KCl = 5.01 kg KCl (to 3 significant figures)