A level chemistry help with a question :)

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xAshley_
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Hi all!

I just wanted an explanation on how to tackle this question, I got 174.64 for the molar mass of A but im unsure if this is right? any help would be appreciated

Bromine reacts with fluorine to form compound A. compound A is a liquid at room temperature and pressure but can easily be vaporised. When vaporised, 0.428g of A produces 76cm^3 of gas at 1.00x10^5 Pa and 373K. Determine the molar mass in gmol^-1 and the molecular formula of A.
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bridiethomas
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I'm not in a position to work it out myself right now but I'm pretty sure it's the ideal gas equation pV=nRT and then rearrange for n which i think is n=pV/RT substitute the values in remembering to convert 76cm3 into m3 and then once you have n (number of moles) then do Mr=mass/moles using the 0.428g and moles you just worked out to get the Mr for A.
Hard to tell if I'm right without actually working it out myself but give it a go.
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5hyl33n
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(Original post by xAshley_)
Hi all!

I just wanted an explanation on how to tackle this question, I got 174.64 for the molar mass of A but im unsure if this is right? any help would be appreciated

Bromine reacts with fluorine to form compound A. compound A is a liquid at room temperature and pressure but can easily be vaporised. When vaporised, 0.428g of A produces 76cm^3 of gas at 1.00x10^5 Pa and 373K. Determine the molar mass in gmol^-1 and the molecular formula of A.
I'm getting a different answer. According to my calculations, the answer is 174.56. :erm:

Did you use the method provided by bridiethomas?
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scimus63
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is it;

Mr = mRT/pV
= (0.428 X 8.31 X 373) / (100 000 X 76 X 10-6)
= 1326.64/7.6
= 174.56
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xAshley_
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(Original post by 5hyl33n)
I'm getting a different answer. According to my calculations, the answer is 174.56. :erm:

Did you use the method provided by bridiethomas?
(Original post by bridiethomas)
I'm not in a position to work it out myself right now but I'm pretty sure it's the ideal gas equation pV=nRT and then rearrange for n which i think is n=pV/RT substitute the values in remembering to convert 76cm3 into m3 and then once you have n (number of moles) then do Mr=mass/moles using the 0.428g and moles you just worked out to get the Mr for A.
Hard to tell if I'm right without actually working it out myself but give it a go.
Thank you both, I think I got slightly confused with converting cm3 into m3 but I see what I did wrong + I got the right answer this time!
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