Question

The enthalpy of solution of nitrous oxide (N₂O) in water is -12 kJ/mol and its solubility at 20 ^oC and 1.00 atm is 0.121 g per 100. g of water. Calculate the molal solubility of nitrous oxide in water at 1.100 atm and 20 ^oC. Hint, first find Henry's law constant at 20 ^oC and 1.00 atm.

Answer 1

we know that

according to henry law

c= K x P

now

we know that

moles = mass / molar mass

so

moles of N20 = 0.121 / 44

moles of N20 = 2.75 x 10-3

now

we know that

molal solubility   = moles of N20 / mass of water (kg)

so

molal solubility of N20 = 2.75 x 10-3 / 0.1

molal solubility of N20 = 0.0275

now

for initial conditions

S = K x P

so

0.0275 = K x 1

K = 0.0275

so

the henry law constant is K

now

for final conditions

S = K x P

S = 0.0275 x 1.1

S = 0.03025

so

the molal solubility at 1.1 atm and 20 C is 0.03025