# Problem: At 20 oC the vapor pressure of benzene C6H6 is 75 torr and that of toluene C7H8 is 22 torr. Assume that benzene and toluene form an ideal solution.In a solution composed of benzene and toluene that has a vapor pressure of 36  torr at 20 oC, what is the mole fraction of toluene?

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###### FREE Expert Solution

Recall that the partial pressure of a gas (PGas)in a mixture is given by:

$\overline{){{\mathbf{P}}}_{{\mathbf{gas}}}{\mathbf{=}}{{\mathbf{\chi }}}_{{\mathbf{gas}}}{{\mathbf{P}}}_{{\mathbf{total}}}}$

where χGas = mole fraction of the gas and Ptotal = total pressure of the gas mixture

Isolating the mole fraction of the gas:

$\frac{{\mathbf{P}}_{\mathbf{gas}}}{{\mathbf{P}}_{\mathbf{total}}}\mathbf{=}\frac{{\mathbf{\chi }}_{\mathbf{gas}}\overline{){\mathbf{P}}_{\mathbf{total}}}}{\overline{){\mathbf{P}}_{\mathbf{total}}}}\phantom{\rule{0ex}{0ex}}\overline{){{\mathbf{\chi }}}_{{\mathbf{gas}}}{\mathbf{=}}\frac{{\mathbf{P}}_{\mathbf{gas}}}{{\mathbf{P}}_{\mathbf{total}}}}$

###### Problem Details

At 20 oC the vapor pressure of benzene C6H6 is 75 torr and that of toluene C7H8 is 22 torr. Assume that benzene and toluene form an ideal solution.

In a solution composed of benzene and toluene that has a vapor pressure of 36  torr at 20 oC, what is the mole fraction of toluene?

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Partial Pressure concept. You can view video lessons to learn Partial Pressure. Or if you need more Partial Pressure practice, you can also practice Partial Pressure practice problems.

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Our tutors rated the difficulty ofAt 20 oC the vapor pressure of benzene C6H6 is 75 torr and t...as medium difficulty.

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What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Singh's class at HCC.