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Amount of substance (concentration question)- help? Watch

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    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
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    48 dm3 of a gas.

    Use 24 dm3 mol-1.
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    (Original post by Pigster)
    48 dm3 of a gas.

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