Determine the vapour pressure of a solution at 55 °C that contains 34.2 g NaCl in 375 mL of water. The vapour pressure of pure water at 55 °C is 0.1574 bar.
A) 0.153 bar
B) 0.127 bar
C) 0.0967 bar
D) 0.108 bar
E) 0.0907 bar

Question

Quizplus · Accepted Answer

The vapor pressure of the solution can be calculated using Raoult's Law. First, calculate the mole fraction of water in the solution. NaCl dissociates into 2 ions (Na+ and Cl-), so the number of moles of ions is doubled. Calculate the moles of NaCl and water, then find the mole fraction of water. Use Raoult's Law to find the vapor pressure: P_solution = X_water * P_pure_water. The closest answer is 0.153 bar.

Determine the Vapour Pressure of a Solution at 55 °C