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    Why does the reaction of copper slowly forming copper oxide and then gradually becoming a layer containing copper sulfate involve oxidation?

    - i know the answer to it i just dont know how to write it


    The layer of copper sulfate forms the blue green patina seen on old copper roofs. Although the patina is only about 60um thick it does not easy cone away from the metal beneath. Explain how the patina protects an old copper roof from further corrosion?
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    Hi,

    Let me walk you through this: Try and remember these two sets of three basic facts (the first set (A = oxidation) of three facts are the opposite of the 2nd set (B = reduction) of three facts (trying to make it easy for you to understand and to remember!):-

    A. Oxidation occurs when any of these happen:
    1. Addition of oxygen
    2. Removal of hydrogen
    3. Loss of an electron

    B. Reduction occurs when any of these happen:
    1. Removal of oxygen
    2. Addition of hydrogen
    3. Gaining an electron

    NOW TO ANSWER YOUR Q.

    When copper is oxidised to copper oxide:

    2Cu + O2 -------> 2CuO

    Oxygen is added to copper, so from A(1) above oxidation of copper occurs. (Happy with this? Gd well done!)

    Also because copper is going from Cu (uncharged copper atom - if you touch your mum's copper saucepan, you do not get an electric shock, do you - no, so copper metal is uncharged, with me?) to Cu+ (one positive charge is present - how did that happen - yes, cool - the copper atom lost an electron (one minus) so it is left with one plus. The item in bold in the previous sentence (look at A(3) above again) tells us that oxidation has taken place.

    IF YOU GET THIS type of Q in exam, look at how many marks it is worth (they always tell you these days!) - if it is worth one mark, just say point A(1) - if it is worth 2 marks, say BOTH A(1) and A(3).

    Easy peasy lemon squeezy, correct?

    M
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    (Original post by macpatelgh)
    Hi,

    Let me walk you through this: Try and remember these two sets of three basic facts (the first set (A = oxidation) of three facts are the opposite of the 2nd set (B = reduction) of three facts (trying to make it easy for you to understand and to remember!):-

    A. Oxidation occurs when any of these happen:
    1. Addition of oxygen
    2. Removal of hydrogen
    3. Loss of an electron

    B. Reduction occurs when any of these happen:
    1. Removal of oxygen
    2. Addition of hydrogen
    3. Gaining an electron

    NOW TO ANSWER YOUR Q.

    When copper is oxidised to copper oxide:

    2Cu + O2 -------> 2CuO

    Oxygen is added to copper, so from A(1) above oxidation of copper occurs. (Happy with this? Gd well done!)

    Also because copper is going from Cu (uncharged copper atom - if you touch your mum's copper saucepan, you do not get an electric shock, do you - no, so copper metal is uncharged, with me?) to Cu+ (one positive charge is present - how did that happen - yes, cool - the copper atom lost an electron (one minus) so it is left with one plus. The item in bold in the previous sentence (look at A(3) above again) tells us that oxidation has taken place.

    IF YOU GET THIS type of Q in exam, look at how many marks it is worth (they always tell you these days!) - if it is worth one mark, just say point A(1) - if it is worth 2 marks, say BOTH A(1) and A(3).

    Easy peasy lemon squeezy, correct?

    M
    Doesn't it go to Cu(2+) in CuO
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    (Original post by LLearnt)
    Doesn't it go to Cu(2+) in CuO
    Yes of course it does - apologies to all who read my post for my middle-age absent-mindedness!!

    So, correction particularly for OP: still oxidation, but looking at point A(3), there is a loss of two electrons not one (leading to production of cupric oxide (having Cu2+ ion[as LLearnt has correctly pointed out) , although copper can also produce a cuprous ion (Cu+) under different conditions.

    Apologies once again and thanks to LLearnt!

    M
 
 
 
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