Join TSR now and get all your revision questions answeredSign up now

Density of ethanoic acid question

    • Thread Starter
    Offline

    2
    ReputationRep:
    Hi guys,

    Doing a bit of AS-level chemistry for revision and I came across this question. I'm not sure whether it's a typo or I'm just looking at it from the wrong angle.

    The question says:

    Calculate the Mr of ethanoic acid and use it to find the concentration of ethanoic acid in g dm^-3.

    So I got the Mr to be approximately 60 and then I used Mr*moles to get the mass so I did 60 * 2.257*10^-3 which gave me 0.13542g in 0.025dm^-3

    0.025 needs to be multiplied by 40 to get 1dm^3 so 0.13542*40=5.4168g dm^-3

    The next part then says:

    The density of pure ethanoic acid is 1.049g cm^-3 Use this value to calculate the concentration of ethanoic acid in vinegar as a volume percentage.

    So I worked out that 1.049g cm^-3 = 1049g dm^-3 but this already doesn't seem right. Can anyone see where I've gone wrong? JN17 ?

    Thanks
    Blake
    Offline

    3
    ReputationRep:
    Could you send the full question please, some numbers from the first part don't make much sense without the question
    What you've done for the second part is correct (the conversion) but again the question doesn't make too much sense
    Offline

    0
    ReputationRep:
    Hi,
    I've come across this question and that is not the correct conversion.

    To get from cm^3 to dm^3 you have to divide by 1000

    So I spoke with another teacher and it's to do with the idea of density!

    The value in the question given is the density of pure ethanoic acid- 1.049 gcm^3. Which is not not mixed with water so you have no concentration. Where as the value we have is derived from a solution of ethanoic acid which Is x1000 more than the value given.
 
 
 
Poll
Which party will you be voting for in the General Election 2017?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.