Commercial grade fuming nitric acid contains about 90% HNO₃ by mass with a density of 1.50 g/mL, calculate the molarity of the HNO₃ solution.

Question

Quizplus · Accepted Answer

The molarity (M) of a solution is calculated using the formula M = (mass of solute in grams / molar mass of solute in grams per mole) / volume of solution in liters. For HNO3 (with a molar mass of approximately 63.01 g/mol), if we have a solution that is 90% HNO3 by mass and has a density of 1.50 g/mL, we first calculate the mass of HNO3 in 1 liter (1000 mL) of solution: 1.50 g/mL * 1000 mL = 1500 g of solution. 90% of this mass is HNO3, so (0.90 * 1500 g = 1350 g of HNO3). The number of moles of HNO3 is then 1350 g / 63.01 g/mol ≈ 21.42 moles. Since this is in 1 liter of solution, the molarity is approximately 21.4 M.

Commercial Grade Fuming Nitric Acid Contains About 90% HNO3 by Mass

Commercial Grade Fuming Nitric Acid Contains About 90% HNO₃ by Mass