What is the vapor pressure at 75°C of an aqueous solution prepared by the addition of 58.4 g of the nonvolatile solute urea,CO(NH₂)₂,to 172 g of water? The vapor pressure of pure water at 75°C is 290.mmHg. A)136 mmHg B)26.8 mmHg C)153 mmHg D)263 mmHg E)216 mmHg

Question

Quizplus · Accepted Answer

To find the vapor pressure of the solution, we use Raoult's law, which states that the vapor pressure of a solution is directly proportional to the mole fraction of the solvent. First, calculate the moles of urea and water. Urea (CO(NH2)2) has a molar mass of approximately 60 g/mol, so 58.4 g of urea is 58.4 g / 60 g/mol = 0.974 moles. Water has a molar mass of 18 g/mol, so 172 g of water is 172 g / 18 g/mol = 9.556 moles. The mole fraction of water is then 9.556 / (9.556 + 0.974) = 0.907. The vapor pressure of the solution is the mole fraction of water times the vapor pressure of pure water, so 0.907 * 290 mmHg = 263 mmHg.

What Is the Vapor Pressure at 75°C of an Aqueous