Final answer:
Without the mole fraction of biphenyl in the solution, the exact vapor pressure cannot be determined, but it will be lower than 100 torr, the vapor pressure of pure benzene at 25°C.
Step-by-step explanation:
The vapor pressure of a solution containing a nonvolatile solute like biphenyl in a solvent such as benzene can be determined using Raoult's Law, which states that the vapor pressure of a solvent over a solution is proportional to the mole fraction of the solvent in the solution. For an ideal solution, the total vapor pressure of the solution is the sum of the vapor pressures of the components multiplied by their respective mole fractions. If biphenyl is nonvolatile, it means that it doesn't contribute to the vapor pressure of the solution. Therefore, the vapor pressure of benzene would decrease proportionally to the amount (mole fraction) of biphenyl present. It's important to know the mole fraction of benzene in the solution to calculate the decrease in vapor pressure compared to the pure solvent. Without further information, the exact vapor pressure cannot be stated, but it would be lower than the vapor pressure of pure benzene, which is given to be 100 torr at 25°C.