Question

The partial pressure of ethane over a saturated solution containing 0.0656g of ethane is 1 bar. If the solution contains 0.0500g of ethane, then what should be the partial pressure of the gas?

• A. 0.762 bar
  
• B. 0.755 bar
  
• C. 0.764 bar
  
• D. 0.772 bar

Answer 1

Answer: (A)

The explanation for the correct option

Option(A). 0.762 bar

• According to Henry's law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas.
• The solubility is given as: $X=K_h\times Pwhere,X=molefraction,P=partialpressure,K_h=henr{y}^{\prime }sconstant$
• Mole fraction is proportional to the mass of the gas.
• For a gas that has a very high solubility, we may assume that the partial pressure of the gas is directly proportional to its mass.
  Here, $P\propto m$
  
  $\Rightarrow \frac{P_2}{P_1}=\frac{m_2}{m_1}$
  
  $\Rightarrow P_2=P_1\times \frac{m_2}{m_1}$
  
  $=1\times \frac{0.05}{0.0656}=0.762$ bar

Hence, Option(A). 0.762 bar is the partial pressure of the gas