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    January 2005 Chemistry by design, just two quick questions:
    1) Nitric acid in the soil can be neutralised with calcium hydroxide, forming calcium nitrate. Use your understanding of structure and bonding to predict three properties of calcium nitrate

    2)
    Ion ----> radius/nm
    Na+ ----> 0.098
    Mg2+ ----> 0.078
    Al3+ ---->0.057

    Explain why the metals form ions with these charges. Say in terms of their atomic structure, what the ions have in common and explain the trend in ionic radium across the period from Na+ to Al3+
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    1) it's ionic so will have a high melting n boiling point. It will be hard but brittle. It will conduct electricity when molten or an electolyte. It will be soluble in water.
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    1. no idea.. i think this is to do with clay minerals which they took out of our syllabus for us.

    2. first part - to do with number of atoms in outershell
    second part - atomic radius becomes lower as u move across the period as you gain more protons and electrons, so theres a stronger force of attraction, so the atom is a little bit smaller

    not sure what they have in common, unless its just that the ions all have complete 2s and 2p orbitals
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    Cheers for hte help
    But i thought it was taken out acouple years ago, as this is the 2005 paper.
    But seriously, i dont see how question 2 is worth 6marks. there surely arent that many points or are they counting some things again?
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    2) They form those ions when they lose their outer electrons. All the element shave the same number of shells. as you go across the period the atomic radius decreases as the number of protons increase giving a greater attraction to the electrons pulling them in more. The ions all have the same number of electrons. Hope thats right!!
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    geekypoo im not sure when they took it out, but i suppose ur right... but saying that threes not much in chemical ideas about nitrates, except that thyre soluble in water (pg255) and i refuse to look at chem storylines cos its just stupid

    so im not sure where it comes into the syllabus at all
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    Well it says in the question to look at teh structure and hte bonding, so i guess that the solubility would be one mark and you could put points about it being ionically bonded, i was thinking like white crystalline solid, dissolves in water, high melting point (dont know why i didnt put down high boiling point???? thanks kat_r for that )
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    just looked at syllabus and in aa, it says relate structure and bonding to properties so i guess the fact that its a nitrate has absolutely nothing to do with minerals im just stupid :/
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    *removes markscheme from bag*
    3di) and 4e right?

    Ok you have to say that
    - charge is determined by electrons in outer shell
    - each of these atoms loses electrons
    - until it has a full (or stable) outer shell
    - once each of these has lost electrons they all have the same number of electrons in the outer shell (a 2,8 arrangement)
    - As you go from Na --> Al there are more protons
    - The more protons there are the closer the electrons are held because the more attractive the nucleus is

    4e:
    It's ionic
    Therefore it will be soluble in water
    And the solution will conduct but the solid will not
    And it will be crystalline
    And it's also white
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    Bekaboo could you possibly send me the Jan05 markscheme? thanks
 
 
 
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