The vapour pressure of benzene at a certain temperature is $640$ mm of Hg. A non-volatile and non-electrolytic solid, weighing $2.175$ g, is added to $39.08$ g of benzene. The vapour pressure of the solution is $600$ mm of Hg. What is the molecular mass (in AMU) of the solid substance?

49.5

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59.6

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69.5

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79.8

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Solution

The correct option is A 69.5
we have,
$\frac{P_{A}^{0} - P_{A}}{P_{A}^{0}} = x_{A} = \frac{n_{A}}{n_{A} + n_{B}}$
$n_{A} << n_{B}$

$\frac{P_{A}^{0} - P_{A}}{P_{A}^{0}} = x_{A} = \frac{n_{A}}{n_{B}}$

$\frac{640 - 600}{640}$ = $\frac{2.175 / M}{39 / 78}$

we get, $M = 69.5$

Hence, option (C) is correct.

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Similar questions

Q. The vapour pressure of benzene at a certain temperature is 640 mm. of Hg. A non-volatile and non-electrolyte solid, weighing 2.175 g is added to 39.08 g of benzene. If the vapour pressure of the solution is 600 mm of Hg. What is the molecular weight of solid substance?

Q. The vapour pressure of pure benzene at a certain temperature is 640 mm Hg. A non-volatile solid weighing 2.175 g is added to 39.0 g of benzene. The vapour pressure of the solution is 600 mm Hg. What is the molecular mass of the solid substance?

The vapour pressure of benzene at a certain temperature is 640mm of Hg. A non volatile and non electrolyte solid weighing 2.175 g is added to 39.08 g of benzene. The vapour pressure of the solution is 600mm of Hg. What is the molecular mass of the solid substance?

Q. The vapour pressure of pure benzene at a certain temperature is 640 mm Hg. A non-volatile non-electrolyte solid weighing 2.175 g is added to 39 g of benzene. The vapour pressure of the solution is 600 mm Hg. What is the molecular weight of the solid substance?

Q. The vapour pressure of pure benzene and at a certain temperature is

640 m m

H g

. A non-volatile, non-electrolyte solid weighing

2.175 g

is added to

39.0 g

of benzene. The vapour pressure of the solution is

600 m m

H g

What is the molecular weight of the solid substance?

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The vapour pressure of benzene at a certain temperature is 640 mm of Hg. A non-volatile and non-electrolytic solid, weighing 2.175 g, is added to 39.08 g of benzene. The vapour pressure of the solution is 600 mm of Hg. What is the molecular mass (in AMU) of the solid substance?

The correct option is A 69.5we have,P0A−PAP0A=xA=nAnA+nBnA<<nBP0A−PAP0A=xA=nAnB640−600640=2.175/M39/78we get, M=69.5 Hence, option (C) is correct.

The vapour pressure of benzene at a certain temperature is $640$ mm of Hg. A non-volatile and non-electrolytic solid, weighing $2.175$ g, is added to $39.08$ g of benzene. The vapour pressure of the solution is $600$ mm of Hg. What is the molecular mass (in AMU) of the solid substance?