Question

Biphenyl, C12H10, is a nonvolatile, non ionizing solute that is soluble in benzene, C6H6. At 25 C, the vapor pressure of pure benzene is 100.84 Torr. What is the vapor pressure of a solution made from dissolving 15.7 g of biphenyl in 29.3 g of benzene?

Answer 1

The vapor pressure of the solution, made from dissolving 15.7 g of biphenyl in 29.3 g of benzene, is 92.03 Torr.

Step-by-step explanation:

To calculate the vapor pressure of the solution, we can use Raoult's Law, which states that the vapor pressure of a solution is proportional to the mole fraction of each component in the solution. First, calculate the mole fraction of benzene and biphenyl. Next, use these mole fractions to determine the partial pressures of each component and then sum them to find the total vapor pressure of the solution.

Given the molecular weights of benzene and biphenyl, we can convert the masses of each into moles. The mole fraction of benzene is then calculated as the moles of benzene divided by the total moles in the solution, and similarly for biphenyl. Using Raoult's Law, the partial pressures of each component are found, and their sum gives the total vapor pressure of the solution.

The final result indicates the vapor pressure of the solution at 25°C, taking into account the presence of both benzene and biphenyl. This approach enables the determination of how the vapor pressure of the solution differs from that of pure benzene, providing insights into the colligative properties of the solution.

Answer 2

The vapor pressure of a solution of biphenyl in benzene at 25 C is calculated using Raoult's Law and is found to be 79.26 Torr.

Step-by-step explanation:

To calculate the vapor pressure of a solution of biphenyl in benzene, we need to apply Raoult's Law, which states that the vapor pressure of a solution is directly proportional to the mole fraction of the solvent.

1. 
   
3. First, we need to calculate the molar mass of biphenyl (C12H10). This is 12(12) + 10(1) = 154 g/mol.
4. 
   
6. Next, we find the moles of biphenyl by dividing the mass by the molar mass, 15.7 g / 154 g/mol = 0.102 moles of biphenyl.
7. 
   
9. For benzene (C6H6), the molar mass is 6(12) + 6(1) = 78 g/mol.
10. 
    
12. We calculate the moles of benzene: 29.3 g / 78 g/mol = 0.375 moles of benzene.
13. 
    
15. The mole fraction of benzene in the solution is the moles of benzene divided by the total moles: 0.375 / (0.375 + 0.102) = 0.786.
16. 
    
18. Finally, we multiply the mole fraction of benzene by the vapor pressure of pure benzene to find the vapor pressure of the solution: 0.786 * 100.84 Torr = 79.26 Torr.

The vapor pressure of the solution at 25 C is 79.26 Torr.