[diablo]

Hi,

anyone got an idea how to solve this ?^^

vapour pressure of pure propanone is given and that 10 g of an involatile substance are dissolved in 75 g of propone. Determine relative molecular mass of involatile substance.

I think it's simple but i dont get it

thx,

Diablooo

[Yggdrasil]

Start with Raoult's law

http://en.wikipedia.org/wiki/Raoult%27s_law

[diablo]

Hey,

thx for u help, i gave some thoughts about it, maybe this one right:

Pi=Pixi  and xi... molefraction ( this for propane)

let's say Pi of propane = 366 ( for example) then the equation looks like this:

366 = 366x npropane/(n propane+n involatile)
since n = m/M, i just have to transform the equation to the M of the involatile substance, right ?^^

thx,

diablooo

[Yggdrasil]

Yup, exactly.

[DevilsDaughter]

And how can I get the M of propane?

[Borek]

I find it hard to believe you were asked to use Raoult's law without being first taught how to calculate molar mass of a compound...

[DevilsDaughter]

there is some basic knowlegde I'm missing..
the problem is that the level of our knowlegde in class is really different....

to the problem:
there is only m of propane....so I'm a little bit confused

[diablo]

hallo ^^

--> hast mail^^

thx for help !