A concentrated sodium hydroxide solution is 50.5% NaOH by mass and has a density of 1.53 g/mL at 25°C.What is the molarity of NaOH?
A)19.3 M
B)0.0612 M
C)8.25 M
D)12.1 M
E)0.0825 M

Question

Quizplus · Accepted Answer

The molarity of a solution is calculated using the formula: Molarity (M) = (mass of solute in grams / molar mass of solute) / volume of solution in liters. For a 50.5% NaOH solution by mass, this means 50.5 grams of NaOH per 100 grams of solution. Given the density of the solution is 1.53 g/mL, 100 grams of solution corresponds to 100 g / 1.53 g/mL = 65.36 mL = 0.06536 L. The molar mass of NaOH is approximately 40 g/mol. Thus, the moles of NaOH in 100 grams of solution are 50.5 g / 40 g/mol = 1.2625 mol. The molarity is then 1.2625 mol / 0.06536 L = 19.3 M.

A Concentrated Sodium Hydroxide Solution Is 50