Hey there! Sign in to join this conversationNew here? Join for free

Amount of substance (concentration question)- help? Watch

    • Thread Starter
    Offline

    8
    ReputationRep:
    Good afternoon,

    I've been working through a booklet of example questions in addition to do doing past papers, I cam across this question and I was completely at a loss as to what to do.
    The original Q:
    Hydrogen chloride is a gas. 48dm3 of hydrogen chloride at room temperature and pressure were dissolved in water and the solution made up to 5dm3.
    Calculate the concentration of the solution of hydrochloric acid.

    Now, I'm not exactly versed in the art of getting 38dm3 in volume of one solution and "making it up (?) to 5dm3".
    So, I presume it should say "up to 50cm3"

    Regardless, how does one go about answering this question?

    Many thanks,
    Sam
    Offline

    17
    ReputationRep:
    48 dm3 of a gas.

    Use 24 dm3 mol-1.
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by Pigster)
    48 dm3 of a gas.

    Use 24 dm3 mol-1.
    Might I ask why you would use that value?
    Offline

    1
    ReputationRep:
    Any gas occupies 24dm3 per mole (under standard conditions) and thats just a fact you have to learn. So you've started off with 2 moles of HCl and dissolved it into 5 dm3, meaning your concentration in mol/dm3 is 2/5 (0.4).

    I hope this helps.
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by JoeT7)
    Any gas occupies 24dm3 per mole (under standard conditions) and thats just a fact you have to learn. So you've started off with 2 moles of HCl and dissolved it into 5 dm3, meaning your concentration in mol/dm3 is 2/5 (0.4).

    I hope this helps.
    Hi,
    Thank you very much for explaining that! I vaguely recall it when we did pv=nrt calculations but it was ever such a long time ago

    Once again, thanks,

    Sam
 
 
 
  • 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
    Did TEF Bronze Award affect your UCAS choices?
  • 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.