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Higher 2010

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  • Message 1. 

    Posted by James (U15527186) on Thursday, 30th May 2013

    Hi there, I was wondering if you could explain to me how to questions 34, 35 and 37 from the 2010 higher past paper?

    Thanks

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  • Message 2

    , in reply to message 1.

    Posted by MissChemTeacher_Bitesize (U15172316) on Thursday, 30th May 2013

    2010 Q34

    Hey James!

    When acid is added to the equilibrium mixture the deep blue complex Cu(NH₃)₄(OH)₂ is broken down as the hydroxide ions react with the hydrogen ions in the acid.

    This in turn will increase the concentration of the substances on the reactants side.

    smiley - cool

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  • Message 3

    , in reply to message 2.

    Posted by MissChemTeacher_Bitesize (U15172316) on Thursday, 30th May 2013

    2010 Q35

    Which of the following is the best description of a 0·1 mol l–1 solution of hydrochloric acid?

    A Dilute solution of a weak acid
    B Dilute solution of a strong acid
    C Concentrated solution of a weak acid
    D Concentrated solution of a strong acid

    Hydrochloric acid is described as being a strong acid because it can fully dissociate (break down) into H+ and Cl- ions when in solution.

    The concentration of the solution is 0.1 mol/l which is considered to be a fairly dilute solution - only 3.65g of HCl in 1 litre of water.

    The answer here would have to be C

    Hope this helps

    Miss_Chem smiley - cool

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  • Message 4

    , in reply to message 3.

    Posted by MissChemTeacher_Bitesize (U15172316) on Thursday, 30th May 2013

    2010 Q37

    When a certain aqueous solution is diluted, its conductivity decreases but its pH remains constant.

    It could be:

    A ethanoic acid
    B sodium chloride
    C sodium hydroxide
    D nitric acid.

    If you dilute an acid or a base the pH of the solution would move towards pH7.

    Sodium chloride is an ionic solution which will conduct electricity., the number of ions in the solution will decrease when diluted reducing how effectively it conducts. It is neutral when dissolved in water so it's pH will not be effected by dilution.

    The answer here would have to be B.

    Hope these explanations are clear. All the best for tomorrow James!

    Miss_Chem smiley - cool

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  • Message 5

    , in reply to message 3.

    Posted by James (U15527186) on Thursday, 30th May 2013

    Thanks, the answer is actually B but I understand smiley - smiley

    Report message5

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