Answer to Question #346412 in General Chemistry for Ne Ne

Question

calculate the vapour pressure of solution at 25°C containing 26.9g of urea CO(NH2)2 in 712g H2O.( Vapour pressure of water at 25°C is 23.8mmHg)

Answer 1

Solution:

The vapour pressure of pure water at 25°C is 23.8 mmHg

The molar mass of water (H₂O) is 18.0153 g/mol

The molar mass of urea (CO(NH₂)₂) is 60.06 g/mol

Determine moles of water and urea:

Moles of water = (712 g water) × (1 mol water / 18.0153 g water) = 39.522 mol water

Moles of urea = (26.9 g urea) × (1 mol urea / 60.06 g urea) = 0.448 mol urea

Determine the mole fraction of the solvent (H₂O):

χ_solvent = (Moles of water) / (Moles of water + Moles of urea)

χ_solvent = (39.522 mol) / (39.522 mol + 0.448 mol) = 0.9888

χ_solvent = 0.9888

Using Raoult's Law, determine the vapour pressure of solution:

P_solution = χ_solvent × P°_solvent

P_solution = (0.9888) × (23.8 mmHg) = 23.53 mmHg

P_solution = 23.53 mmHg

Answer: The vapour pressure of solution is 23.53 mmHg