Henry’s law constant for the molality of methane in benzene at 298 K is 4.27 × 105 mm Hg. The solubility of methane in benzene at 298 K under 760 mm Hg is -

1. 1.78 x 10-3

2. 1.78 x 10-5

3. 2.98 x 10-4

4. 3.78 x 10-3

Hint: Formula of Henry's law; P=kHXsolute
Step 1:
The given values are as follows:

Here, p = 760 mm Hg

kH = 4.27 × 10mm Hg

According to Henry’s law,

p=kHx

Step 2:

Calculate the mole fraction of solute as follows:
x=pkH
=760 mm Hg4.27×105 mm Hg
=177.99×10-5  
=1.78×10-3 (approximately)

Hence, the mole fraction of methane in benzene is 1.78 × 10−3.