Final answer:
The partial pressure of N2 is calculated by multiplying the total pressure (785 torr) by the approximate mole fraction (0.78), yielding about 612.3 torr. However, this value is not given in the options, suggesting there may be a discrepancy in the presented values or question details.
Step-by-step explanation:
To calculate the partial pressure and mole fraction of N2, we'll use the given information that the sample of dry air at 785 torr and 25 degrees Celsius contains 0.925 moles of N2. The partial pressure of N2 can be calculated by multiplying the mole fraction of N2 by the total pressure of the air sample.
The mole fraction of N2 is given as the ratio of moles of N2 to the total moles of air. Since air is approximately 78% nitrogen, we can assume that the mole fraction is close to 0.78 for nitrogen in air. However, since we are provided the moles of N2 explicitly, we'll use that value:
Mole fraction of N2 = moles of N2 / total moles of air = 0.925 / (0.925 + other gases)
To find the other gases, we can apply the ideal gas law to find total moles given the conditions, but since this isn't provided, we'll assume air is mostly N2, and because its 0.925 moles, we can use the approximate mole fraction of 0.78, derived from the typical composition of air.
Partial pressure of N2 = total pressure * mole fraction of N2 = 785 torr * 0.78 ≈ 612.3 torr (which is not among the given options, indicating a possible misconception in the question or provided values).