Question

The partial pressure of ethane over a solution containing 6.56 × 10⁻³ g of ethane is 1 bar. If the solution contains 5.00 × 10⁻² g of ethane, then what shall be the partial pressure of the gas?

Answer 1

Molar mass of ethane (C₂H₆) = 2 × 12 + 6 × 1

= 30 g mol⁻¹

Number of moles present in 6.56 × 10⁻² g of ethane

= 2.187 × 10⁻³ mol

Let the number of moles of the solvent be x.

According to Henry’s law,

p = K_Hx

(Since x >> 2.187 × 10⁻³)

Number of moles present in 5.00 × 10⁻² g of ethane

= 1.67 × 10⁻³ mol

According to Henry’s law,

p = K_Hx

(Since, x >> 1.67 × 10⁻³)

= 0.764 bar

Hence, partial pressure of the gas shall be 0.764 bar.