The vapor pressure of chloroform is 173.11 mmHg at 25 ∘C. How many grams of aspirin,C2H8O4, a nonvolatile, nonelectrolyte (MW=180.1 g/mol), must be added to 238.0grams of chloroform to reduce the vapor pressure to 168.73 mmHg? chloroform=CHCl3=119.40 g/mol
Question
The vapor pressure of chloroform is 173.11 mmHg at 25 ∘C. How many grams of aspirin,C2H8O4, a nonvolatile, nonelectrolyte (MW=180.1 g/mol), must be added to 238.0grams of chloroform to reduce the vapor pressure to 168.73 mmHg? chloroform=CHCl3=119.40 g/mol
Solution
This problem can be solved using Raoult's Law, which states that the vapor pressure of a solution is equal to the mole fraction of the solvent times the vapor pressure of the pure solvent.
First, we need to calculate the mole fraction of chloroform in the final solution. The mole fraction is equal to the moles of chloroform divided by the total moles in the solution.
The vapor pressure of the solution is given as 168.73 mmHg, and the vapor pressure of pure chloroform is given as 173.11 mmHg. Therefore, the mole fraction of chloroform in the solution is 168.73/173.11 = 0.9747.
Next, we need to calculate the moles of chloroform in the solution. The mass of chloroform is given as 238.0 g, and the molar mass of chloroform is given as 119.40 g/mol. Therefore, the moles of chloroform is 238.0 g / 119.40 g/mol = 1.993 moles.
Now we can calculate the total moles in the solution. The total moles is equal to the moles of chloroform divided by the mole fraction of chloroform, which is 1.993 moles / 0.9747 = 2.045 moles.
Finally, we can calculate the moles of aspirin in the solution. The moles of aspirin is equal to the total moles minus the moles of chloroform, which is 2.045 moles - 1.993 moles = 0.052 moles.
To find the mass of aspirin, we multiply the moles of aspirin by the molar mass of aspirin. The molar mass of aspirin is given as 180.1 g/mol, so the mass of aspirin is 0.052 moles * 180.1 g/mol = 9.37 g.
Therefore, 9.37 grams of aspirin must be added to the chloroform to reduce the vapor pressure to 168.73 mmHg.
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