Question

A 10 mL of 120 mg/L solution of Styrene in water is injected into a 125 mL vial at 20°C.

What will be the gas phase concentration at equilibrium?

The Henry's Constant for Styrene is K_H= 2.60 atm•L/mol

The molar mass of Styrene is 104 g/mol

Other Info:

R= 0.08206 atm•L/mole•K = 1.987 cal/mole•K = 8.314 J/mole•K

1 Joule = Newton • Meter

1 atm = 1.013 X 10⁵ N/m² = 1.013 X 10⁵ Pa

1 gallon = 3.785 L

Answer 1

Molar mass of Styrene = 104g/mol

mass of Styrene = 0.120g

mole of Styrene = 0.120g/104g= 0.001154

Molarity of Styrene = 0.001154M

Henry's law is

p =K_H C

where, p = partial pressure of the solute

C = Concentration of solute , 0.001154M

K_{H = Henry's law constant for styrene , 2.60atm mol /L}

p = 2.60(atm L/mol ) × 0.001154 (mol/L)

= 0.0030atm

Ideal gas equation is

PV = nRT

n/V = P/RT

= 0.0030atm / (0.082057(L atm /mol K) × 293.15K)

= 0.000125M

Therefore, gas phase Concentration of Styrene is 0.000125M