A concentrated aqueous ammonia solution has a density of 0.90 g/mL and is 28.0% ammonia by mass. Determine the molar concentration of this solution.
A)15 M
B)1.5 M
C)0.032 M
D)31 M
E)3.0 M

Question

Quizplus · Accepted Answer

To find the molar concentration (molarity, M), we first calculate the mass of ammonia in 1 liter (1000 mL) of solution. Given the density (0.90 g/mL) and the mass percentage of ammonia (28.0%), the mass of ammonia in 1000 mL is 0.90 g/mL * 1000 mL * 0.28 = 252 g. The molar mass of ammonia (NH3) is approximately 17.03 g/mol. Therefore, the molarity is 252 g / 17.03 g/mol = 14.8 M, which rounds to 15 M, making choice A correct.

A Concentrated Aqueous Ammonia Solution Has a Density of 0