Question

The concentration of commercially available concentrated nitric acid is 70.0 percent by mass, or 15.9 M. Calculate the density and molality of the solution.

Answer 1

Answer:

Density = 1000 g/l

= 1.00 kg/l.

Molality = 0.037 mol/g

= 37 mol/kg.

Explanation:

Molar concentration of nitric acid = 15.9 M.

Mass of water in 100 g = 100 - 70

= 30 g

Mass of nitric acid = 70 g

Molar mass of HNO3 = 1 + 14 + (16*3)

= 63 g/mol

Number of moles = mass/molar mass

= 70/63

= 1.11 mol.

Molar concentration = number of moles/volume

Volume = 1.11/15.9

= 0.07 l

Density = mass/volume

Density =

= 70 * 0.07

= 1000 g/l

= 1.00 kg/l

Molality = number of moles of nitric acid/mass of solvent(water)

= 1.11/0.030

= 37 mol/kg