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

    16
    ReputationRep:
    Silver chloride has a more exothermic lattice enthalpy than sodium chloride. however it has a lower melting point. doesn't a more exothermic lattice enthalpy means you need more energy to overcome the bonding and so shouldn't it have a higher melting point?
    the text book says that the melting point supports the argument that silver chloride has a greater degree of covalency but i fail to see how being slightly covalent means it is more exothermic.
    is it to do with the ratio of ions and not packing so well that it has a lower melting point?

    Thanks!
    • Community Assistant
    • Study Helper
    Offline

    14
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by Goods)
    Silver chloride has a more exothermic lattice enthalpy than sodium chloride. however it has a lower melting point. doesn't a more exothermic lattice enthalpy means you need more energy to overcome the bonding and so shouldn't it have a higher melting point?
    the text book says that the melting point supports the argument that silver chloride has a greater degree of covalency but i fail to see how being slightly covalent means it is more exothermic.
    is it to do with the ratio of ions and not packing so well that it has a lower melting point?

    Thanks!
    The only explanation I can think of for this is that when AgCl melts the lattice is not completely disrupted and molecular type species are formed, perhaps AgCl molecules ...?

    This would also fit with the discrepancy between the experimental and theoretical values for the lattice enthalpy. The fact that experimental is greater than theoretical suggests that there is a contribution from covalency.
    Offline

    2
    ReputationRep:
    (Original post by Goods)
    Silver chloride has a more exothermic lattice enthalpy than sodium chloride. however it has a lower melting point. doesn't a more exothermic lattice enthalpy means you need more energy to overcome the bonding and so shouldn't it have a higher melting point?
    the text book says that the melting point supports the argument that silver chloride has a greater degree of covalency but i fail to see how being slightly covalent means it is more exothermic.
    is it to do with the ratio of ions and not packing so well that it has a lower melting point?

    Thanks!
    Covalent bonds are stronger than ionic bonds (it's why diamond is so hard), so perhaps that is why it is more exothermic.
 
 
 
  • 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
    Would you like to hibernate through the winter months?
  • 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.