Question

Concentrated nitric acid is 15.6M and has a density of 1.41g/mL. What is the weight percent of concentrated HNO3?

Answer 1

molarity= mol/ liters

since the molarity is given, we can assume that we have 1.0 Liters of solution

15.6 M= mol/ 1 liters---> this means that we have 15.6 moles of HNO3

we need to convert these moles to grams using the molar mass of HNO3

molar mass  HNO3= 1.01 + 14.0 + (3 X 16.0)= 63.01 g/mol

15.6 mol HNO3 (63.01 g/ mol)= 983 grams HNO3

now we have to determine the grams of solution using the assumption of 1 liters of solution and the density

1 liters= 1000 mL

1000 mL (1.41 g/ ml)= 1410 grams solution

mass percent= mass of solute/ mass of solution x 100

mass percent= 63.01/ 1410 x 100= 4.47 %