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

    20
    ReputationRep:
    Calculate the number of atoms present in 1kg of 226 88 Ra?

    So I did (88 x 1.00728)+(138 x 1.00867)= 227.8371 Amu/molar mass
    then 227.8371 x 6.02x10^23 (avogadro's constant) to get 1.37..x10^26 which was wrong.

    How do you do these types of question? Is there a better way to work out the number of atoms?
    Thanks
    Offline

    4
    ReputationRep:
    (Original post by Lay-Z)
    Calculate the number of atoms present in 1kg of 226 88 Ra?

    So I did (88 x 1.00728)+(138 x 1.00867)= 227.8371 Amu/molar mass
    then 227.8371 x 6.02x10^23 (avogadro's constant) to get 1.37..x10^26 which was wrong.

    How do you do these types of question? Is there a better way to work out the number of atoms?
    Thanks
    So the mass of an atom of 226 Ra is 227.8371u (assuming your calc is correct). That is 3.782*10^(-25) kg. (I have multiplied by u).

    So the number of atoms in 1kg is 1 /(3.782*10^(-25)) = 2.64*10^(24)

    Alternatively, the number of moles is 1000/(227.8371) (by moles = mass/ mr) (remember to work in grams) and then you can multiply this number by avogradro's constant
    • Thread Starter
    Offline

    20
    ReputationRep:
    thanks
 
 
 
  • 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
    Brexit voters: Do you stand by your vote?
  • 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

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