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 of solution = 1.43 g/mL

Molality → mol/kg = 37 m

Explanation:

The solute is HNO₃

Molar mass → 63 g/mol

70 % by mass → 70 g of solute / 100 g of solution

We convert the mass of HNO₃ to moles → 70 g / 63 g/mol = 1.11 moles

So let's apply molarity to find out the volume of our moles.

Molarity (M)  = mol/L →  mol / M  = L → 1.11  mol / 15.9 M = 0.070 L

This is the volume for solution. We can convert it from L to mL

0.070 L . 1000 mL / 1L = 70 mL

As the mass of solution = 100 g → Density = Mass/Volume

100g / 70 mL = 1.43 g/mL

Molality → mol of solute / kg of solvent

Solution mass = 100 g → Mass of solute + Mass of solvent

Mass of solvent = 30 g

We convert the mass of solvent from g to kg → 30 g . 1kg / 1000 g = 0.030 kg

Molality (mol/kg) → 1.11 mol / 0.030 kg = 37 m