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    (Original post by ThatMadClown)
    the best thing to do would be writing that answer in your notes. Im on AQA and we do the silver nitrate test.
    Cheers! It's an old paper so maybe it's not on the papers anymore but I might as well I think!
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    http://qualifications.pearson.com/co...e_20110113.pdf

    May someone explain to me why in Q6a) why Answer A can be completely ruled out?
    and I don't get Q11)

    thankyou
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    Out of curiosity to those of you doing the Empa on AQA, when are you doing this?
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    I am going over Hess' law cycles and I can't seem to remember why standard enthalpy change of formation always needs 1 mole of product on the right hand side and why combustion always has 1 mole of elements and compounds on the left side of the equation.

    All I know is that it does! But whyyy?

    Thanks
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    (Original post by Super199)
    Out of curiosity to those of you doing the Empa on AQA, when are you doing this?
    The week after easter

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    (Original post by TheonlyMrsHolmes)
    I am going over Hess' law cycles and I can't seem to remember why standard enthalpy change of formation always needs 1 mole of product on the right hand side and why combustion always has 1 mole of elements and compounds on the left side of the equation.

    All I know is that it does! But whyyy?

    Thanks
    Because that's the definition:
    " Energy change of formation is the energy change when 1 mole of a compound is formed from its constituent elements in their standard states under standard conditions(298K 1atm)

    Energy change of combustion is the energy when 1 mole of a substance is completely burned in an excess of oxygen under standard conditions " "

    May you look at my post and help me please? I forgot about those things


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    (Original post by frozo123)
    Because that's the definition:
    " Energy change of formation is the energy change when 1 mole of a compound is formed from its constituent elements in their standard states under standard conditions(298K 1atm)

    Energy change of combustion is the energy when 1 mole of a substance is completely burned in an excess of oxygen under standard conditions " "

    May you look at my post and help me please? I forgot about those things


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    Oh right thank you, thats be not bothering to look at my definitions lol and yeah sure one sec!
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    (Original post by frozo123)
    http://qualifications.pearson.com/co...e_20110113.pdf

    May someone explain to me why in Q6a) why Answer A can be completely ruled out?
    and I don't get Q11)

    thankyou
    For Question 6, successive ionisation energy is the energy required to remove each electron in turn. Each successive ionisation energy is larger than the last, as more there is one less electron, so there is less electron repulsion, therefore the outer shell electrons are a tiny bit closer to the nucleus (meaning more energy is required to remove it). However, there is an even bigger jump in ionisation energies between shells, as electrons in inner shells are much closer to the nucleus than those in outer shells, and this can be seen on the graph where there are larger jumps than usual.

    On the graph, there is at least 1 jump in energies which is between 3rd and 4th ionisation energies. Therefore, after the 3rd electron being removed, there is a new shell (I am ignoring the jump between 1st and 2nd ionisation energies, as that would imply that there would be 1 electron in the outer shell, then only 2 electrons in the next shell, which is not possible since it isn't the innermost shell)so it can't be in Group 1, as Group 1 elements only have 1 electron in the outer shell.

    Hope this helped!
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    (Original post by frozo123)
    http://qualifications.pearson.com/co...e_20110113.pdf

    May someone explain to me why in Q6a) why Answer A can be completely ruled out?
    and I don't get Q11)

    thankyou
    For 6a) Answer A can be completely rules out because group 1 has only 1 electron in it's outer shell, the graph shows 10 electrons being removed.

    Q11)It says that most compounds of lead are insoluble, basically inferring that if you add sulphuric acid to lead the lead will dissolve, but then it tells us that lead(II)nitrate is an exception to this. Then all the options but C include Lead(II) nitrate solution (1st clue) and all the others include adding sulphuric acid to other lead compounds (2nd clue ). There for the answer must be C.

    Hope that helped!
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    (Original post by lukejoshjames)
    For Question 6, successive ionisation energy is the energy required to remove each electron in turn. Each successive ionisation energy is larger than the last, as more there is one less electron, so there is less electron repulsion, therefore the outer shell electrons are a tiny bit closer to the nucleus (meaning more energy is required to remove it). However, there is an even bigger jump in ionisation energies between shells, as electrons in inner shells are much closer to the nucleus than those in outer shells, and this can be seen on the graph where there are larger jumps than usual.

    On the graph, there is at least 1 jump in energies which is between 3rd and 4th ionisation energies. Therefore, after the 3rd electron being removed, there is a new shell (I am ignoring the jump between 1st and 2nd ionisation energies, as that would imply that there would be 1 electron in the outer shell, then only 2 electrons in the next shell, which is not possible since it isn't the innermost shell)so it can't be in Group 1, as Group 1 elements only have 1 electron in the outer shell.

    Hope this helped!

    I really don't understand why there is a jump between 1st and 2nd ionisation energies? stupid graph!
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    Yeah, I think they've just done that to catch you out. I wouldn't be able to explain why that happens (maybe something to do with electron shielding?) xD As long as you think logically about how many electrons are in each shell, though, it shouldn't be to difficult.
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    (Original post by TheonlyMrsHolmes)
    For 6a) Answer A can be completely rules out because group 1 has only 1 electron in it's outer shell, the graph shows 10 electrons being removed.

    Q11)It says that most compounds of lead are insoluble, basically inferring that if you add sulphuric acid to lead the lead will dissolve, but then it tells us that lead(II)nitrate is an exception to this. Then all the options but C include Lead(II) nitrate solution (1st clue) and all the others include adding sulphuric acid to other lead compounds (2nd clue ). There for the answer must be C.

    Hope that helped!
    you mean soluble in the first line right?
    but yeah thankyou it made sense
    For your question about ionisation energies
    I think the graph is of aluminium as the first electron being removed is from the 3p subshell, the consequent electrons are being removed from the 3s subshell, hence the significant jump, as there is less shielding, and the effective nuclear charge is greater
    I'm an A2 student, just doing unit 1 papers to recall my knowledge haha which is slowly coming back
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    (Original post by lukejoshjames)
    For Question 6, successive ionisation energy is the energy required to remove each electron in turn. Each successive ionisation energy is larger than the last, as more there is one less electron, so there is less electron repulsion, therefore the outer shell electrons are a tiny bit closer to the nucleus (meaning more energy is required to remove it). However, there is an even bigger jump in ionisation energies between shells, as electrons in inner shells are much closer to the nucleus than those in outer shells, and this can be seen on the graph where there are larger jumps than usual.

    On the graph, there is at least 1 jump in energies which is between 3rd and 4th ionisation energies. Therefore, after the 3rd electron being removed, there is a new shell (I am ignoring the jump between 1st and 2nd ionisation energies, as that would imply that there would be 1 electron in the outer shell, then only 2 electrons in the next shell, which is not possible since it isn't the innermost shell)so it can't be in Group 1, as Group 1 elements only have 1 electron in the outer shell.

    Hope this helped!
    great answer thankyou
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    (Original post by lukejoshjames)
    Yeah, I think they've just done that to catch you out. I wouldn't be able to explain why that happens (maybe something to do with electron shielding?) xD As long as you think logically about how many electrons are in each shell, though, it shouldn't be to difficult.
    read above
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    (Original post by frozo123)
    you mean soluble in the first line right?
    but yeah thankyou it made sense
    For your question about ionisation energies
    I think the graph is of aluminium as the first electron being removed is from the 3p subshell, the consequent electrons are being removed from the 3s subshell, hence the significant jump, as there is less shielding, and the effective nuclear charge is greater
    I'm an A2 student, just doing unit 1 papers to recall my knowledge haha which is slowly coming back
    By bad :facepalm: Basically my explanation but flipped around!

    (I also can't take away the bold writing so excuse that please)

    Q11)It says that most compounds of lead are insoluble, basically inferring that if you add sulphuric acid to lead the lead will not dissolve, but then it tells us that lead(II)nitrate is an exception to this and it will dissolve. Then all the options but C include Lead(II) nitrate solution (
    1st clue) and all the others include adding sulphuric acid to other lead compounds (2nd clue ). There for the answer must be C.

    I had to write the correct explanation sorry if you already understood! haha

    and thanks for explaining the other bit!
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    (Original post by TheonlyMrsHolmes)
    I am going over Hess' law cycles and I can't seem to remember why standard enthalpy change of formation always needs 1 mole of product on the right hand side and why combustion always has 1 mole of elements and compounds on the left side of the equation.

    All I know is that it does! But whyyy?

    Thanks
    Becaue thats what the definition of standard enthalpy of formation is.. The amount of energgy needed for ONE mole of substance to be formed. If the moles of product on the right side of the reaction were different for every reaction, it would be hard to compare enthalpy changes, its just the standard for all reactions. Kinda like relative atomic mass is the mass of an element compared to carbon 12 which is seen as the standard.
    Obvioulsy the enthalpy change for three moles of a compound to be formed will be gfeater than one mole, but we just want to know the basic standard.
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    I'm doing OCR B Salters.

    I was just wondering, what would you say is the best way to revise chemistry?
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    (Original post by TheonlyMrsHolmes)
    By bad :facepalm: Basically my explanation but flipped around!

    (I also can't take away the bold writing so excuse that please)

    Q11)It says that most compounds of lead are insoluble, basically inferring that if you add sulphuric acid to lead the lead will not dissolve, but then it tells us that lead(II)nitrate is an exception to this and it will dissolve. Then all the options but C include Lead(II) nitrate solution (
    1st clue) and all the others include adding sulphuric acid to other lead compounds (2nd clue ). There for the answer must be C.

    I had to write the correct explanation sorry if you already understood! haha

    and thanks for explaining the other bit!
    If you have any questions, let me know as it helps with my revision
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    Anyone know the equations relating to moles, avogadro and number of atoms.
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    (Original post by chzm)
    Becaue thats what the definition of standard enthalpy of formation is.. The amount of energgy needed for ONE mole of substance to be formed. If the moles of product on the right side of the reaction were different for every reaction, it would be hard to compare enthalpy changes, its just the standard for all reactions. Kinda like relative atomic mass is the mass of an element compared to carbon 12 which is seen as the standard.
    Obvioulsy the enthalpy change for three moles of a compound to be formed will be gfeater than one mole, but we just want to know the basic standard.

    Not doing alevels however, doing Applied science.. haven't revised.. but could u ask me a random alevel chem q? and any alevel biology question e.g. topics such as: cell membrane, biological molecules, cells e.t.c..
 
 
 
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