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    "give the ionic equation including state symbols for the reaction between solid magnesium oxide and hydrochloric acid. This reaction is of metal oxide + acid -----> salt + water

    MgO(s) + 2H+ -----> Mg2+ + H2O

    Is that right?
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    yes
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    (Original post by shengoc)
    A question like this can come up,

    1) Why is no indicator used for the reaction?

    or

    2) How would you determine the end point of titration/reaction?

    Then obviously, knowing that there is a colour change is going to answer those questions!
    Yeah, i get there will be a colour change now but is there any other colour changes i need to know about? thanks for your reply mate
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    (Original post by boromir9111)
    Yeah, i get there will be a colour change now but is there any other colour changes i need to know about? thanks for your reply mate
    other reactions that are sort of self indicating include titration with KMnO4 with Fe2+, it goes from purple to ?

    These are the most common ones i know of.
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    (Original post by shengoc)
    other reactions that are sort of self indicating include titration with KMnO4 with Fe2+, it goes from purple to ?

    These are the most common ones i know of.
    it goes from purple to pink. Ahh, that of course as well. Thanks mate
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    for NMR the splitting patterns, i only need to be aware of pascal's triangle right?
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    (Original post by boromir9111)
    for NMR the splitting patterns, i only need to be aware of pascal's triangle right?
    ermm, why don't you look up in your exam board syllabus?
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    (Original post by shengoc)
    ermm, why don't you look up in your exam board syllabus?
    Well i only knew that splitting pattern was related to pascal's triangle on TSR and that was after looking at my syllabus and reading the materials..... pointless info they gave. If they give you the info you need, you can retrace back to the source and that increases your knowledge. But i just wanted to be sure that's all i needed to know.

    Also, this is a query on weak acid/strong acids and bases etc. The difference between them of course is proton partially dissociates or fully dissociates.... what does that exactly mean tbh?
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    (Original post by boromir9111)
    Well i only knew that splitting pattern was related to pascal's triangle on TSR and that was after looking at my syllabus and reading the materials..... pointless info they gave. If they give you the info you need, you can retrace back to the source and that increases your knowledge. But i just wanted to be sure that's all i needed to know.

    Also, this is a query on weak acid/strong acids and bases etc. The difference between them of course is proton partially dissociates or fully dissociates.... what does that exactly mean tbh?
    Well, different exam boards/schools would use the appropriate textbooks, surely what is in your textbooks could be asked in the exams, so learn them well.

    Acid dissociation, hmm, let say
    HX ----> H+ + X-

    For strong acid, the eqm lies very much to the right, that the acid dissociation constant(similar to eqm constant) is therefore much greater than 1. 1 is the eqm point(dynamic eqm).

    For weak acid, the eqm lies very much to the left, not much dissociation, because the conjugate base is not stabilised enough(well any value of Ka below 1 would result in LHS being favoured).
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    (Original post by shengoc)
    Well, different exam boards/schools would use the appropriate textbooks, surely what is in your textbooks could be asked in the exams, so learn them well.

    Acid dissociation, hmm, let say
    HX ----> H+ + X-

    For strong acid, the eqm lies very much to the right, that the acid dissociation constant(similar to eqm constant) is therefore much greater than 1. 1 is the eqm point(dynamic eqm).

    For weak acid, the eqm lies very much to the left, not much dissociation, because the conjugate base is not stabilised enough(well any value of Ka below 1 would result in LHS being favoured).
    Ahh, yes of course now it's coming back to me..... thanks for that mate
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    http://www.thepaperbank.co.uk/papers...2007_jan_w.pdf

    question 2 (b)..... it's only worth one mark, am i missing something here?

    edit - is it to the equilibrium itself? since it's a forward reaction there will be a lot of PCl3 and Cl2 and not a lot of PCl5. Since Kc is proportional to PCl5..... do we just sub in the numbers???
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    (Original post by boromir9111)
    http://www.thepaperbank.co.uk/papers...2007_jan_w.pdf

    question 2 (b)..... it's only worth one mark, am i missing something here?

    edit - is it to the equilibrium itself? since it's a forward reaction there will be a lot of PCl3 and Cl2 and not a lot of PCl5. Since Kc is proportional to PCl5..... do we just sub in the numbers???
    It is just qualitative, either an increase or decrease.

    Alright, Kc is less than one meaning LHS is favoured.
    So, we would expect to get more of the reactants(LHS), therefore PC5 would increase to more than its starting amount.

    As LHS is being favoured and more PCl5 is being produced, the RHS yields drop. Both are involved in making up PCl5 so both would decrease.
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    (Original post by shengoc)
    It is just qualitative, either an increase or decrease.

    Alright, Kc is less than one meaning LHS is favoured.
    So, we would expect to get more of the reactants(LHS), therefore PC5 would increase to more than its starting amount.

    As LHS is being favoured and more PCl5 is being produced, the RHS yields drop. Both are involved in making up PCl5 so both would decrease.
    Ahhh, of course always relate to Kc. Since Kc is low(low meaning less than 1) then reaction is very much to the left hence it increases and therefore RHS as you said would drop. Thanks mate for that, i have given you +rep
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    what is the molecular formula of ibuprofen?......
    http://www.thepaperbank.co.uk/papers...2006_jan_w.pdf

    I am getting this basic 1 marker wrong..... someone please explain!!!

    question 4 b (i)

    edit - lol, i got it, it's C13H18O2, i just couldn't get the H part right but realised where i was going wrong.
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    http://www.thepaperbank.co.uk/papers...2006_jan_w.pdf

    More importantly the two step reaction i am concerned with...... how do i go about doing this?

    Also, the last question has me confused.... do i do the ratio of C:O or CO2: H2O or both??????

    actually i get the following : moles of CO2 = 3.74/44 = 0.085, moles of H2O = 0.051
    mass of C = (12/44) * 3.74 = 1.02g, mass of H = (2/18) * 0.918 = 0.102g

    therefore mass of O = 1.394 - (0.102+1.02) = 0.272g

    moles of Eugenol = 1.394/164 = 0.0085 moles but how do i get moles of O when it's part of CO2 and H2O?

    edit - problem solved!!!!!
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    anyone?
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    http://www.thepaperbank.co.uk/papers...2007_jan_w.pdf

    question 3 d please
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