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    (Original post by Freddy12345)
    I don't understand these questions and exams are just around the corner:
    Question 1:

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    Investigation of the rate of reaction between HCl acid and pure Magnesium, in which the following curve (Above is obtained)

    The reaction is exothermic:

    Explain why, using your understanding of collision theory to express why the line is curved and not straight?
    As the reaction proceeds the hydrogen ions are used up and there are less collisions. The rate consequentially decreases.
    Next part is of a different reaction:

    Two reasons for why the hazard associated with he formation of sulfur dioxide in this investigation might be considered to be low:

    Na(2)S(2)O(3) (aq) + 2HCl (aq) = 2NaCl (aq) + S (s) SO(2) (aq) + H(2)O (l)
    It is a very soluble gas. Little of it is released from solution.
    Question:

    Pure magnesium reacts completely with excess dilute sulfuric acid. The reaction of pure Calcium with excess dilute sulfuric acid is very rapid initially. The reaction then slows down and stops before all the calcium has reacted.

    Use you knowledge of group 2 sulfates and solubility of group 2 sulfates to express why the reactions of magnesium and calcium differ?
    Calcium sulphate is insoluble and the formation of an insoluble layer on the surface of the calcium prevents access by the hydrogen ions of the sulphuric acid. The reaction cannot continue.

    Question:

    Iron (ll) Ethanedioate is an insoluble solid used as a pigment in paints and glass it occurs as a dihydrate (FeC(2)O(4) . 2H(2)O)

    One way of preparing Iron (ll) ethanedioate is outlined below:

    Procedure:

    6.95g of sample hydrated iron(ll) Sulfate (FeSO(4) . 7H2O) was added to 100 cm3 of water in a beaker.

    150cm3 volume of 0.20 mol dm-3 sodium ethanedioate solution was added to the beaker. the mixture was stirred until precipitation was complete. After filtration, 3.51g of the dihydrate (FeC(2)O(4).2H(2)O ) were collected.

    It then asks to calculate percentage yield Mr of iron(ll) ethandioate = 179.8

    It then goes on to ask why the yield is less than 100%, but the experiment had no side reactions the reagents were pure and the reaction goes to completion.
    Nothing is 100% insoluble. Some may be left in solution or stuck to the filter paper or not rinsed out of the flask. Any experiment loses product.


    Then there is a titration question which I am lost at:

    When dissolved in dilute sulfuric acid, the number of moles of ethanedioate ions in a pigment can be determined by titration with acidified potassium Manganate (VII)

    Explain why titration of a sample of Iron (ll) Ethanedioate would require a different amount of Potassium Manganate (VII) than a titration of equimolar amount of copper (ll) ethanedioate.

    What does it mean by equimolar?
    Equimolar = same number of moles

    Different amount are needed because in the iron(II) ethandioate both of the ions can be oxidised by the manganate(VII) ions

    Also:

    How does a precipitate become dry in a dissicator?
    It's a DESSICATOR.

    The drying agent in the dessicator removes the water vapour from the air, stimulating the precipitate to lose water as vapour, as the equilibrium water(l) <==> water(g) ratio must remain constant.
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    (Original post by charco)
    As the reaction proceeds the hydrogen ions are used up and there are less collisions. The rate consequentially decreases.

    It is a very soluble gas. Little of it is released from solution.

    Calcium sulphate is insoluble and the formation of an insoluble layer on the surface of the calcium prevents access by the hydrogen ions of the sulphuric acid. The reaction cannot continue.

    Nothing is 100% insoluble. Some may be left in solution or stuck to the filter paper or not rinsed out of the flask. Any experiment loses product.

    Equimolar = same number of moles

    Different amount are needed because in the iron(II) ethandioate both of the ions can be oxidised by the manganate(VII) ions


    It's a DESSICATOR.

    The drying agent in the dessicator removes the water vapour from the air, stimulating the precipitate to lose water as vapour, as the equilibrium water(l) <==> water(g) ratio must remain constant.
    I don't understand your answer for the graph as it asks why the line is curved.

    and for the equimolar question, what do you mean by both can be oxidised and would it need more or less?

    Are you sure that the calcium is insoluble or is it less soluble?
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    part 1
    the rate is increasing BECAUSE it's exothermic, any successful collision will release heat energy, and provide more energy to unreacted particles
    This was posted from The Student Room's Android App on my GT-S5830i
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    (Original post by PKMN TRN JAM)
    part 1
    the rate is increasing BECAUSE it's exothermic, any successful collision will release heat energy, and provide more energy to unreacted particles
    This was posted from The Student Room's Android App on my GT-S5830i
    So what does this have to do with the line being a curve?
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    Why has it given me the Mr to work out percentage yield, I don't understand..
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    (Original post by Freddy12345)
    So what does this have to do with the line being a curve?
    The curve shows the rate of reaction increasing, which can be explained because it is exothermic
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    Ok but why did it give me the Mr for percentage yield..
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    (Original post by Freddy12345)
    rrr
    You need it to find out how many moles of iron(II) ethandioate have been formed....
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    (Original post by charco)
    You need it to find out how many moles of iron(II) ethandioate have been formed....
    Why
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    (Original post by charco)
    You need it to find out how many moles of iron(II) ethandioate have been formed....
    Can you how me how please??/
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    aren't these the chemistry ISA exam questions?
 
 
 
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