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Topic: Mass required to raise the boiling point of 44.6 mL of benzene to 81.2ºC?  (Read 2747 times)

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Offline webassignbuddy

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The boiling point of benzene (Mm = 78.0 g/mol; kb = 2.53ºC/m; ρ = 0.877 g/mL) is 80.1ºC. What mass of vanillin (mm = 152.1 g/mol; non-electrolyte) is required as a solute to raise the boiling point of 44.6 mL of benzene to 81.2ºC?

Solvent (benzene)
b  = 80.1ºC
kb  = 2.53ºC/m
ΔTb = 81.2ºC
Mm = 78.9 g/mol
ρ = 0.877 g/mL
V = 44.6 mL

Solute (vanillin)
Mm = 152.1 g/mol
i = 1 (non-electrolyte)

ΔTb = kbmc
ΔTb = kb(1 * m)
ΔTb = kb(1 * mol solute/mass kg solvent)
81.2 = (2.53)(mol solute/___ mass kg solvent)

Solve for mass kg solvent (benzene)
44.6 mL x 0.877 g/mL = 39.1142 g = 0.039 kg solvent, right?

Am I on the right track??

Offline Borek

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Re: Mass required to raise the boiling point of 44.6 mL of benzene to 81.2ºC?
« Reply #1 on: December 09, 2013, 04:09:51 PM »
81.2 = (2.53)(mol solute/___ mass kg solvent)

Think it over.
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Offline webassignbuddy

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Re: Mass required to raise the boiling point of 44.6 mL of benzene to 81.2ºC?
« Reply #2 on: December 09, 2013, 04:11:20 PM »
81.2 = (2.53)(mol solute/___ mass kg solvent)

Think it over.

I did and I can't figure out how I got marked wrong up to here.
The final is tomorrow and I'm stressing out trying to figure out how to solve this one :(
I have no idea why they gave my Mm of benzene also!

Offline webassignbuddy

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Re: Mass required to raise the boiling point of 44.6 mL of benzene to 81.2ºC?
« Reply #3 on: December 09, 2013, 04:39:00 PM »
81.2 = (2.53)(mol solute/___ mass kg solvent)

Think it over.

Oh wait nvm I figured it out.

1.1 = (2.53)(mol solute/0.039)

And then I just multiply mol solute by 152.1 g vanillin.

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