Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    4
    ReputationRep:
    How would I go about answering this question?

    A molecule has an empirical formula of C3H7O, and a relative molecular mass of 118.
    Deduce the molecular formula of the molecule.
    Offline

    11
    ReputationRep:
    Empirical formula is the simplified version of an compound's chemical formula, meaning that the ratios of the different elements in the compound are simplified to 3:7:1 (C : H : O). Given the RMM of the real compound, using the ratio you need to work out what the chemical formula of the real compound.

    So, firstly, find out the RMM of the empirical compound: [(12*3)+(1*7)+(16*1)] = 36+7+16= 59 = RMM of C3H7O.
    To get the mass from 59 to 118, you multiply 59 by 2, meaning that essentially the real compound is 2 times the simplified empirical formula, so = 2*(C3H7O) = C6H14O2.

    I hope this makes sense. Sorry if it doesn't
    Offline

    12
    ReputationRep:
    I agree with above ^^ You find the empirical formula and divide it by the molar mass to get an integer number.
    • Thread Starter
    Offline

    4
    ReputationRep:
    (Original post by marniedavies03)
    Empirical formula is the simplified version of an compound's chemical formula, meaning that the ratios of the different elements in the compound are simplified to 3:7:1 (C : H : O). Given the RMM of the real compound, using the ratio you need to work out what the chemical formula of the real compound.

    So, firstly, find out the RMM of the empirical compound: [(12*3)+(1*7)+(16*1)] = 36+7+16= 59 = RMM of C3H7O.
    To get the mass from 59 to 118, you multiply 59 by 2, meaning that essentially the real compound is 2 times the simplified empirical formula, so = 2*(C3H7O) = C6H14O2.

    I hope this makes sense. Sorry if it doesn't
    Ah yes I think I've understood it now. Thank you for your help.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    What newspaper do you read/prefer?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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.