When a certain amount of solid A is dissolved in 100 g of water at 25°C to make a dilute solution, the vapour pressure of the solution is reduced to one-half of that of pure water. The vapour pressure

Question

When a certain amount of solid A is dissolved in 100 g of water at 25°C to make a dilute solution, the vapour pressure of the solution is reduced to one-half of that of pure water. The vapour pressure of pure water is 23.76 mmHg. The number of moles of solute A added is

Canvas Classes · Accepted Answer

Strategy:
 According to Raoult's Law (), find the required mole fraction of the solute and then determine the moles needed.

Step 1: Determine the required mole fraction ()
The vapour pressure is reduced to one-half: .

Step 2: Calculate moles of water
Mass = 100 g. Molar mass = 18 g/mol.

Step 3: Solve for moles of solute ()

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