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GCSE AQA C3 CHEMISTRY UNIT 3 OFFICIAL UNOFFICIAL MARK SCHEME. Weds 14th June 2017 watch

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    Hello. Here's the C3 mark scheme for all you that been waiting for it. Please don't forget to follow me for future mark schemes. (and don't forget to give reps). Enjoy!

    1ai) Rainwater is soft How does rainwater become hard? [2]
    falls onto rocks such as limestone and gysum/epsom, dissolving Mg2+ ions and Ca2+ ions. This makes the water hard

    1aii) Graph shows Magnesium solubility. What conclusions can be made from the graph? [2]
    more magnesium dissolves upto a temperature of 68 degrees, and then decreases after that. The rate of solubility increase is faster than rate of decrease

    1aii) give one advantage and one disadvantage of hard water [2]
    advantage: aids development of teeth/bones(many others but this is what i put)
    disadvantage: lots more soap needed to make lather so expensive(many more....)


    1b) How do ion exchange columns remove hardness of water [3]
    contains resins which have Na+ or H+ ions in them, as the hard water flows through them, these ions replace the Mg2+ and Ca2+ in the water, thus meaning it now contains sodium or hydrogen ions, and no calcium/magnesium ions. This means it's now soft.

    2a) Draw the displayed structure of ethanoic acid [1]
    you add two hydrogens to the second C and add the functional group '-COOH-'.

    2b) tick the box which shows the correct formula for methanol [1]
    top one (CH3OH)

    2bii) (tickbox) Which Graph shows the overall energy change during combustion of alcohol? [1]
    i ticked the third one


    2c) Describe how the student could use the apparatus shown to compare the energy released from burning ethanol and methanol.
    In your answer you should
    include any measurements the student should make
    not include any reference to calculations
    not include any improvements to apparatus [6]
    i really cannot be asked to be honest

    2d) The energy released was less than what it was stated in the book. Suggest one improvement to the apparatus to make results more accurate. [2]
    lid - reduces any energy loss by evaporation
    OR
    Metal calorimeter - no energy lost in heating the container, as metal is a better conductor (There are plenty of mark schemes which havemore improvements - cba rn)


    4ai) Why did Mendeleev leeve(pun intended ) gaps? [1]
    for undiscovered elements


    4aii) Dimitri Mendeleev organised the elements in the periodic table. Suggest reason why Ti, V and Cr are not in the right place [1]
    they are all metals and their groups contain non metals, so incorrect


    4bi) explain, In terms of electrons, why bromine is in group 7. [1]
    has 7 electrons in outer shell, same as chlorine and fluorine

    4bii) The equation above shows that Bromine is more reactive than Iodine. Explain why, in terms of electrons [3]
    Bromine can attract an electron easier than Iodine, because the distance it has less shells, and so the distance between the nucleus and the outermost electrons, thus meaning a stronger force of attraction. Iodine has weaker force of attraction, so can gain electron less easily...etc etc. Thus by being able to gain electron easier, bromine is more reactive


    5ai) Complete and balance the equation for the reaction of Potassium
    with water [2]
    ...2...K + ...2...H20 => ...2...KOH + H2

    5aii) suggest two differences between reaction of water with lithium and reaction of water with potassium [2]
    potassium - bubbling much more vigorously and produces lilac flame


    5b) Describe how the student could use the apparatus to find out the volume of KOH solution need to neutralise 25.00cm cubed of nitric acid [5]
    CBA


    5c) during the titration 26.25cm cubed of 0.2 molar Potassium hydroxide solution was needed to neutralise 25cm cubed of nitric acid. Work out the concentration of the Nitric acid [3]
    0.0265 x 0.2 = 0.025 x C
    C = 0.21 Moles

    5d) Explain why ethanoic acid has a higher pH than Hydrochloric acid in solution [2]
    Hcl ionises completely and not reversible reaction and so higher H+ ion concentration. Ethanoic acid doesn't fully ionise as ions react again to form ethanoic acid. thus weaker pH for ethanoic acid



    5ei) Ion testing, write down the colour of the precipitate when AgNO3 solution is added to something iodide [1]
    yellow

    5eii) What is the colour of the precipitate when NaOH solution is added to Iron(II)Chloride? [1]
    Green

    5eiii) Explain why a flame test would not show potassium and sodium in the salt [1]
    flames will be masked/mix with each other/lilac masks yellow

    5f) Explain how someone and tell magnesium chloride aluminium chloride apart using NaOH solution [2]
    adding excess causes Al3+ ions to dissolve, but excess to magnesium will not make it dissolve, so you can tell them apart



    6a) Below is an equation for the use of sulphur in industry . Explain why a moderately high temperature is used for this reaction [3]
    a lower temperature means slow rate of reaction but higher exothermic yield. A higher temperature means endothermic reaction favoured but faster rate, thus a compromise is reached where the moderate high temperature means fast rate a good exothermic yield


    6b) Explain why you might expect this reaction to be conducted under high pressure [2]
    higher pressure favours the reaction with least number molecules, so favours forward reaction(use given equation) thus more yield


    6c) The reaction is done at atmospheric pressure, not high pressure. Suggest one reason for this [1]
    SO3 is a gas so dangerous at high pressure


    6di) THIS QUESTION WAS ********
    What is the relationship between wealth of a country and the amount of Ethene and Sulfur acid [2]
    greater wealth means more production of ethene, so a positive relationship. Sulfuric acid production doesn't show clear relationship, as it increased from country D onwards, but decreased from country A to country D, so indistinct relation


    6dii) Suggest one reason for increase in ethene production for a country [1]
    Needed to produce ethanol for fuel

    7a) name the source of hydrogen gas for haber bosch [1]
    natural gas

    7b) describe how ammonia is separated from unreacted Nitrogen and hydrogen[2]
    has highest boiling point out of all 3 gases, so cooled to -33 degrees and it condenses easily, due to the other gases' boiling point being significantly lower


    7c) calculate the energy change for the decomposition of hydrazine [2]
    1724 - 1805 = (-)81kJ




    7d) the reaction in part (a) is exothermic, Explain this in terms of bonds forming and breaking [2]
    energy needed to break bonds is less than energy released by forming bonds, so overall more energy released, thus exothermic




    Once again guys, remember to share and give a thumbs up!
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    (Original post by mahmed69)
    Hello. Here's the C3 mark scheme for all you that been waiting for it. Please don't forget to follow me for future mark schemes. (and don't forget to give reps). Enjoy!

    1ai) Rainwater is soft How does rainwater become hard? [2]
    falls onto rocks such as limestone and gysum/epsom, dissolving Mg2+ ions and Ca2+ ions. This makes the water hard

    1aii) Graph shows Magnesium solubility. What conclusions can be made from the graph? [3]
    more magnesium dissolves upto a temperature of 68 degrees, and then decreases after that. The rate of solubility increase is faster than rate of decrease

    1aii) give one advantage and one disadvantage of hard water [2]
    advantage: aids development of teeth/bones(many others but this is what i put)
    disadvantage: lots more soap needed to make lather so expensive(many more....)


    1b) How do ion exchange columns remove hardness of water [3]
    contains resins which have Na+ or H+ ions in them, as the hard water flows through them, these ions replace the Mg2+ and Ca2+ in the water, thus meaning it now contains sodium or hydrogen ions, and no calcium/magnesium ions. This means it's now soft.

    2a) Draw the displayed structure of ethanoic acid [1]
    you add two hydrogens to the second C and add the functional group '-COOH-'.

    2b) tick the box which shows the correct formula for methanol [1]
    top one (CH3OH)

    2bii) (tickbox) Which Graph shows the overall energy change during combustion of alcohol? [1]
    i ticked the third one


    2c) Describe how the student could use the apparatus shown to compare the energy released from burning ethanol and methanol.
    In your answer you should
    include any measurements the student should make
    not include any reference to calculations
    not include any improvements to apparatus [6]
    i really cannot be asked to be honest

    2d) The energy released was less than what it was stated in the book. Suggest one improvement to the apparatus to make results more accurate. [2]
    lid - reduces any energy loss by evaporation
    OR
    Metal calorimeter - no energy lost in heating the container, as metal is a better conductor (There are plenty of mark schemes which havemore improvements - cba rn)


    4ai) Why did Mendeleev leeve(pun intended ) gaps? [1]
    for undiscovered elements


    4aii) Dimitri Mendeleev organised the elements in the periodic table. Suggest reason why Ti, V and Cr are not in the right place [1]
    they are all metals and their groups contain non metals, so incorrect


    4bi) explain, In terms of electrons, why bromine is in group 7. [1]
    has 7 electrons in outer shell, same as chlorine and fluorine

    4bii) The equation above shows that Bromine is more reactive than Iodine. Explain why, in terms of electrons [3]
    Bromine can attract an electron easier than Iodine, because the distance it has less shells, and so the distance between the nucleus and the outermost electrons, thus meaning a stronger force of attraction. Iodine has weaker force of attraction, so can gain electron less easily...etc etc. Thus by being able to gain electron easier, bromine is more reactive


    5ai) Complete and balance the equation for the reaction of Potassium
    with water [2]
    ...2...K + ...2...H20 => ...2...KOH + H2

    5aii) suggest two differences between reaction of water with lithium and reaction of water with potassium [2]
    potassium - bubbling much more vigorously and produces lilac flame


    5b) Describe how the student could use the apparatus to find out the volume of KOH solution need to neutralise 25.00cm cubed of nitric acid [5]
    CBA


    5c) during the titration 26.25cm cubed of 0.2 molar Potassium hydroxide solution was needed to neutralise 25cm cubed of nitric acid. Work out the concentration of the Nitric acid [3]
    0.0265 x 0.2 = 0.025 x C
    C = 0.21 Moles

    5d) Explain why ethanoic acid has a higher pH than Hydrochloric acid in solution [2]
    Hcl ionises completely and not reversible reaction and so higher H+ ion concentration. Ethanoic acid doesn't fully ionise as ions react again to form ethanoic acid. thus weaker pH for ethanoic acid



    5ei) Ion testing, write down the colour of the precipitate when AgNO3 solution is added to something iodide [1]
    yellow

    5eii) What is the colour of the precipitate when NaOH solution is added to Iron(II)Chloride? [1]
    Green

    5eiii) Explain how someone and tell magnesium chloride aluminium chloride apart using NaOH solution [2]
    adding excess causes Al3+ ions to dissolve, but excess to magnesium will not make it dissolve, so you can tell them apart



    6a) Below is an equation for the use of sulphur in industry . Explain why a moderately high temperature is used for this reaction [3]
    a lower temperature means slow rate of reaction but higher exothermic yield. A higher temperature means endothermic reaction favoured but faster rate, thus a compromise is reached where the moderate high temperature means fast rate a good exothermic yield


    6b) Explain why you might expect this reaction to be conducted under high pressure [2]
    higher pressure favours the reaction with least number molecules, so favours forward reaction(use given equation) thus more yield


    6c) The reaction is done at atmospheric pressure, not high pressure. Suggest one reason for this [1]
    SO3 is a gas so dangerous at high pressure


    6di) THIS QUESTION WAS ********
    What is the relationship between wealth of a country and the amount of Ethene and Sulfur acid [2]
    greater wealth means more production of ethene, so a positive relationship. Sulfuric acid production doesn't show clear relationship, as it increased from country D onwards, but decreased from country A to country D, so indistinct relation


    6dii) Suggest one reason for increase in ethene production for a country [1]
    Needed to produce ethanol for fuel

    7a) calculate the energy change for the decomposition of hydrazine [3]
    1724 - 1805 = (-)81kJ




    7b) the reaction in part (a) is exothermic, Explain this in terms of bonds forming and breaking [2]
    energy needed to break bonds is less than energy released by forming bonds, so overall more energy released, thus exothermic




    Once again guys, remember to share and give a thumbs up!
    Wow!! Amazing mark scheme
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    6 di) was C2 wasn't it??
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    (Original post by mahmed69)
    Hello. Here's the C3 mark scheme for all you that been waiting for it. Please don't forget to follow me for future mark schemes. (and don't forget to give reps). Enjoy!

    1ai) Rainwater is soft How does rainwater become hard? [2]
    falls onto rocks such as limestone and gysum/epsom, dissolving Mg2+ ions and Ca2+ ions. This makes the water hard

    1aii) Graph shows Magnesium solubility. What conclusions can be made from the graph? [3]
    more magnesium dissolves upto a temperature of 68 degrees, and then decreases after that. The rate of solubility increase is faster than rate of decrease

    1aii) give one advantage and one disadvantage of hard water [2]
    advantage: aids development of teeth/bones(many others but this is what i put)
    disadvantage: lots more soap needed to make lather so expensive(many more....)


    1b) How do ion exchange columns remove hardness of water [3]
    contains resins which have Na+ or H+ ions in them, as the hard water flows through them, these ions replace the Mg2+ and Ca2+ in the water, thus meaning it now contains sodium or hydrogen ions, and no calcium/magnesium ions. This means it's now soft.

    2a) Draw the displayed structure of ethanoic acid [1]
    you add two hydrogens to the second C and add the functional group '-COOH-'.

    2b) tick the box which shows the correct formula for methanol [1]
    top one (CH3OH)

    2bii) (tickbox) Which Graph shows the overall energy change during combustion of alcohol? [1]
    i ticked the third one


    2c) Describe how the student could use the apparatus shown to compare the energy released from burning ethanol and methanol.
    In your answer you should
    include any measurements the student should make
    not include any reference to calculations
    not include any improvements to apparatus [6]
    i really cannot be asked to be honest

    2d) The energy released was less than what it was stated in the book. Suggest one improvement to the apparatus to make results more accurate. [2]
    lid - reduces any energy loss by evaporation
    OR
    Metal calorimeter - no energy lost in heating the container, as metal is a better conductor (There are plenty of mark schemes which havemore improvements - cba rn)


    4ai) Why did Mendeleev leeve(pun intended ) gaps? [1]
    for undiscovered elements


    4aii) Dimitri Mendeleev organised the elements in the periodic table. Suggest reason why Ti, V and Cr are not in the right place [1]
    they are all metals and their groups contain non metals, so incorrect


    4bi) explain, In terms of electrons, why bromine is in group 7. [1]
    has 7 electrons in outer shell, same as chlorine and fluorine

    4bii) The equation above shows that Bromine is more reactive than Iodine. Explain why, in terms of electrons [3]
    Bromine can attract an electron easier than Iodine, because the distance it has less shells, and so the distance between the nucleus and the outermost electrons, thus meaning a stronger force of attraction. Iodine has weaker force of attraction, so can gain electron less easily...etc etc. Thus by being able to gain electron easier, bromine is more reactive


    5ai) Complete and balance the equation for the reaction of Potassium
    with water [2]
    ...2...K + ...2...H20 => ...2...KOH + H2

    5aii) suggest two differences between reaction of water with lithium and reaction of water with potassium [2]
    potassium - bubbling much more vigorously and produces lilac flame


    5b) Describe how the student could use the apparatus to find out the volume of KOH solution need to neutralise 25.00cm cubed of nitric acid [5]
    CBA


    5c) during the titration 26.25cm cubed of 0.2 molar Potassium hydroxide solution was needed to neutralise 25cm cubed of nitric acid. Work out the concentration of the Nitric acid [3]
    0.0265 x 0.2 = 0.025 x C
    C = 0.21 Moles

    5d) Explain why ethanoic acid has a higher pH than Hydrochloric acid in solution [2]
    Hcl ionises completely and not reversible reaction and so higher H+ ion concentration. Ethanoic acid doesn't fully ionise as ions react again to form ethanoic acid. thus weaker pH for ethanoic acid



    5ei) Ion testing, write down the colour of the precipitate when AgNO3 solution is added to something iodide [1]
    yellow

    5eii) What is the colour of the precipitate when NaOH solution is added to Iron(II)Chloride? [1]
    Green

    5eiii) Explain how someone and tell magnesium chloride aluminium chloride apart using NaOH solution [2]
    adding excess causes Al3+ ions to dissolve, but excess to magnesium will not make it dissolve, so you can tell them apart



    6a) Below is an equation for the use of sulphur in industry . Explain why a moderately high temperature is used for this reaction [3]
    a lower temperature means slow rate of reaction but higher exothermic yield. A higher temperature means endothermic reaction favoured but faster rate, thus a compromise is reached where the moderate high temperature means fast rate a good exothermic yield


    6b) Explain why you might expect this reaction to be conducted under high pressure [2]
    higher pressure favours the reaction with least number molecules, so favours forward reaction(use given equation) thus more yield


    6c) The reaction is done at atmospheric pressure, not high pressure. Suggest one reason for this [1]
    SO3 is a gas so dangerous at high pressure


    6di) THIS QUESTION WAS ********
    What is the relationship between wealth of a country and the amount of Ethene and Sulfur acid [2]
    greater wealth means more production of ethene, so a positive relationship. Sulfuric acid production doesn't show clear relationship, as it increased from country D onwards, but decreased from country A to country D, so indistinct relation


    6dii) Suggest one reason for increase in ethene production for a country [1]
    Needed to produce ethanol for fuel

    7a) calculate the energy change for the decomposition of hydrazine [3]
    1724 - 1805 = (-)81kJ




    7b) the reaction in part (a) is exothermic, Explain this in terms of bonds forming and breaking [2]
    energy needed to break bonds is less than energy released by forming bonds, so overall more energy released, thus exothermic




    Once again guys, remember to share and give a thumbs up!
    can you do c2 please?
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    (Original post by Hahajsjsh1201)
    Jeez not even a please? Be more greatful in future u little s***
    i did say please?
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    OMG THANKYOU even though ik I already lost like 10 marks
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    What would the grade boundaries be like?
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    this mark scheme is obviously bull **** how can i get 54 cmon now mo...
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    and 2d didnt specify one improvement
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    and i said purple flame instead of lilac would i get the mark?
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    (Original post by mahmed69)
    Hello. Here's the C3 mark scheme for all you that been waiting for it. Please don't forget to follow me for future mark schemes. (and don't forget to give reps). Enjoy!

    1aii) Graph shows Magnesium solubility. What conclusions can be made from the graph? [3]
    more magnesium dissolves upto a temperature of 68 degrees, and then decreases after that. The rate of solubility increase is faster than rate of decrease
    I swear it was up to 64 degrees not 68, I might be wrong, just off the top of my head.
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    (Original post by shaan 101010)
    and i said purple flame instead of lilac would i get the mark?
    Yes im sure you would
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    (Original post by Darusmaka)
    I swear it was up to 64 degrees not 68, I might be wrong, just off the top of my head.
    I got 68.
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    what will the grade boundaries be like?
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    (Original post by EdexcelAreIdiots)
    I got 68.
    Reconsidering I think I put 68 also, just my mind was remembering it weirdly.
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    Hey, that's an amazing mark scheme. love the effort put into it. Will you be releasing a C2 mark scheme?
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    (Original post by shaan 101010)
    and i said purple flame instead of lilac would i get the mark?
    Yes, almost certainly
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    Why was it minus 81? I got plus 81 (
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    (Original post by RedRain)
    Yes, almost certainly
    I put pink flame :argh:
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    (Original post by SoughtJames)
    Hey, that's an amazing mark scheme. love the effort put into it. Will you be releasing a C2 mark scheme?
    Yes it is out, just click this : https://www.thestudentroom.co.uk/sho...4#post72156674

    there may be some marks not correctly allocated as i couldnt remember them as well as C3, due to it being first
 
 
 
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