Source: Extra Practice
What is the molarity of a solution prepared by dissolving 4.0 g of NaOH in enough water to form 250 mL of solution?
Options
Option A
0.1 M
Option B is correct
0.4 M
Option C
1.0 M
Option D
0.25 M
Explanation
Molarity (M) = Moles of solute / Volume of solution in Liters. Molar mass of NaOH = 23 + 16 + 1 = 40 g/mol. Moles of NaOH = 4.0 / 40 = 0.1 mol. Volume = 250 mL = 0.250 L. Molarity = 0.1 / 0.250 = 0.4 M. Option 0.1 M is the number of moles, not molarity. 1.0 M and 0.25 M are incorrect calculations.