Question

Oxalic Acid, H2C2O4, occurs at the potassium or calcium salt in many plants. An aqueous solution of oxalic acid is 0.580 m. The density of the solution is 1.022 g/ml. What is the molar concentration?

Answer 1

Let mass of solvent be 1 Kg

use:

molality = number of mol of H2C2O4 / mass of solvent in Kg

0.580 = number of mol of H2C2O4 / 1 Kg

number of mol of H2C2O4 = 0.580 mol

Molar mass of H2C2O4,

MM = 2*MM(H) + 2*MM(C) + 4*MM(O)

= 2*1 + 2*12 + 4*16

= 90 g/mol

mass of H2C2O4,

m = number of mol * molar mass

= 0.580*90

= 52.2 g

So,

mass os solution = mass of solvent + mass of H2C2O4

= 1000 g + 52.2 g

= 1052.2 g

density of solution = 1.022 g/mL

So,

mass of solution = density * volume

1052.2 g = 1.022 g/mL * volume

volume = 1029.5 mL

volume = 1.0295 L

now use:

molarity = number of mol of H2C2O4 / volume

= 0.580 mol / 1.0295 L

= 0.563 M

Answer: 0.563 M