Answer to Question #302105 in General Chemistry for Hutchii

Question

The concentrated sulfuric acid that we use in the laboratory is 98.0 % H2SO4 by mass. Calculate the molality and molarity of the solution. The density of the solution is 1.83 g/mL.

Answer 1

Mass of H2 SO4 = 98%

Means 98gm of H2 SO4 solute are present per 100gm of solution.

Hence mass of H2SO4 solute = 98gm.

Molar mass of H2SO4 solute =molar mass = (1.008 g/mol × 2) + (32.07 g/mol × 1) + (16.00 g/mol × 4)

Molar mass = 98.086 g/mol

Mass of solution = volume x density

= 1000 x 1.83 = 1830 g

Mass of H2SO4 = 98.0/100 x 1830 = 1793.4 g

Moles of H2SO4 = mass/molar mass of H2SO4

= 1793.4/98.08

= 18.3 mol

Molarity = No. Of moles of H2SO4 solute / Volume of solution in l

=18.3/1

=18.3M

Therefore, the molarity of

solution H2SO4 is 18.3 M

Molality = moles of H2SO4/mass of water in kg

= 18.3/0.0366

= 500 mol/kg = 500m