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    Hello everyone.

    This is a thread for those people who are doing Higher Chemistry for the 2016/17 session.

    Discuss anything related to the course, and post some of your study resources here or ask questions whenever you need help etc etc

    How's everyone finding the course so far? We've been doing Unit 1 (Chemical Changes and Structures). I think it's been going fine so far, However there's a lot more to memorise as expected. We're close to finishing unit 1 already according to my teacher :O
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    Hey.
    We've started with Unit 3 Chemistry in Society to get all the calculations stuff out out the way first. It's alright, mostly just logic and maths so far but I'm more excited for the other parts of the course like the nature's chemistry unit which looks more interesting.


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    (Original post by Sherlock222)
    Hey.
    We've started with Unit 3 Chemistry in Society to get all the calculations stuff out out the way first. It's alright, mostly just logic and maths so far but I'm more excited for the other parts of the course like the nature's chemistry unit which looks more interesting.


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    Ohh cool Is there any new formulas in Unit 3? Or is it a continuation of the previous ones? I'd imagine there's some new ones in there, But just asking anyway.

    Yeah Unit 2 looks really interesting! Can't wait to start it
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    (Original post by A+Hunter)
    Ohh cool Is there any new formulas in Unit 3? Or is it a continuation of the previous ones? I'd imagine there's some new ones in there, But just asking anyway.

    Yeah Unit 2 looks really interesting! Can't wait to start it
    Well there's stuff like atom economy, percentage yield and gas calculations but they're quite straight forward and in the data booklet.
    The Equilibria stuff is a little hard to get your head around but it's quite interesting



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    Hey.
    We've just moved on to intermolecular and intramolecular bonding. It's been going fine so far! Pretty straight forward, but that can change within a period lol
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    Hi, could anyone help me with this question?
    It's from a past paper and driving me mad...

    1. The level of hypochlorite in swimming pools needs to be maintained between 1 and 3 parts per million (1 – 3 ppm).

    400 cm3 of a commercial hypochlorite solution will raise the hypochlorite level of 45 000 litres of water by 1 ppm. Calculate the volume of hypochlorite solution that will need to be added to an Olympic-sized swimming pool, capacity 2, 500, 000 litres, to raise the hypochlorite level from 1 ppm to 3 ppm.
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    I did Higher last year and I got an A. If you need any help just give me a shout.
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    (Original post by BVB09AubaXVII)
    I did Higher last year and I got an A. If you need any help just give me a shout.
    hi could you help me with this question

    a student obtained a certain volume of carbon dioxide by the reaction of 20cm^3 of 2 moll hydrochloric acid with excess sodium carbonate.

    2HCL+Na2CO3=2NaCL+CO2

    which solution of sulfuric acid would give the same final volume of carbon dioxide when added to excess sodium carbonate.
    H2SO4+Na2CO3=Na2SO4+CO2

    a)10cm^3 of 2 moll sulfuric acid
    b)20cm^3 of 2 moll sulfuric acid
    c)10cm^3 of 4moll of sulfuric acid
    d)20cm^3 of 4 moll of sulfuric acid
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    hi can someone help me with this question

    respiration provides energy for the body through"combustion" of glucose. the equation for the enthalpy of combustion of glucose is:

    C6H12O6+6O2=6CO2+6H2O+6H2O enthalpy=-2807kJmoll

    calculate the volume of oxygen in litres, required to provide 418kJ of energy. (take the molar volume of oxygen to be 24 litres mol-1)
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    (Original post by jackiemcnair)
    hi could you help me with this question

    a student obtained a certain volume of carbon dioxide by the reaction of 20cm^3 of 2 moll hydrochloric acid with excess sodium carbonate.

    2HCL+Na2CO3=2NaCL+CO2

    which solution of sulfuric acid would give the same final volume of carbon dioxide when added to excess sodium carbonate.
    H2SO4+Na2CO3=Na2SO4+CO2

    a)10cm^3 of 2 moll sulfuric acid
    b)20cm^3 of 2 moll sulfuric acid
    c)10cm^3 of 4moll of sulfuric acid
    d)20cm^3 of 4 moll of sulfuric acid
    You use the molar ratios in the above balanced equation to find out how much CO2 was produced in the HCl experiment and using that, find out the matching volume of CO2 produced. What do you think the answer is?
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    I just finished unit 2. We have our nab this week and I was wondering if anyone had any resources I could use.
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    (Original post by Ethan100)
    I just finished unit 2. We have our nab this week and I was wondering if anyone had any resources I could use.
    Scholar, BBC bite size(has an app as well).
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    (Original post by RossB1702)
    Scholar, BBC bite size(has an app as well).
    Thanks

    What do you think I should focus on ?
    I find the ending of the unit pretty difficult
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    (Original post by Ethan100)
    Thanks

    What do you think I should focus on ?
    I find the ending of the unit pretty difficult
    I would cover drawing structures of esters, proteins, Amino acids etc, uv light reactions(initiation, propagation, termination), soaps and emulsions. I think they might cover the majority of the questions.
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    (Original post by Ethan100)
    I just finished unit 2. We have our nab this week and I was wondering if anyone had any resources I could use.
    Same got a NAB coming up as well.

    Have you done any practice ones yet?
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    Currently revising for prelim.

    Does anyone have resources for specific exam questions on unit 1?
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    (Original post by Ethan100)
    Currently revising for prelim.

    Does anyone have resources for specific exam questions on unit 1?
    http://new.chemistry-teaching-resour...PPGuidance.pdf

    There aren't many but this is useful.
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    Can someone explain to me Van Der Walls forces?

    I'm just not getting it, whatever I read, I still don't get it.

    I find Hydrogen bonds easiest to understand but it's the PDPD and London Dispersion forces.

    I know that LDF are the weakest of VDW forces and they are formed when there is an unequal distribution of electrons throughout a molecule or atom...(Is that correct?)
    What is an induced dipole and an instantaneous dipole?

    Thanks in advance!
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    (Original post by Ethan100)
    Can someone explain to me Van Der Walls forces?

    I'm just not getting it, whatever I read, I still don't get it.

    I find Hydrogen bonds easiest to understand but it's the PDPD and London Dispersion forces.

    I know that LDF are the weakest of VDW forces and they are formed when there is an unequal distribution of electrons throughout a molecule or atom...(Is that correct?)
    What is an induced dipole and an instantaneous dipole?

    Thanks in advance!
    Van der waals forces consist of 3 intermolecular forces: hydrogen bonding, LDF and PD/PD interactions.

    The understanding you have of LDF is correct, so that's alright for now.

    A PD/PD occurs when there is a difference in electronegativity in a molecule. Remember electronegativity is a measure of the strength of attraction an element has for its shared electrons. So if you take a molecule with a large difference in negativity, the electrons will be pulled towards the more electronegative atom. This is because it is smaller and the strength of attraction operates over a smaller distance than it does in a larger one. So this results in a permanent dipole since the electrons are pulled towards one side of the molecule, creating a slightly negative charge. In contrast, on the opposite side of the molecule the deficiency in electrons (due to them being pulled towards the more electronegative side) will result in a slightly posture charge.

    An induced dipole is basically when a other dipole (temporary if I remember back correctly) is formed due to close contact with a temporary dipole, where the slightly negative side of the temporary dipole repels the electrons of the other atom. On the other side of the induced atom, the deficiency of electrons results in a slightly positive charge. So they are therefore held by LDF in this way.

    I'm pretty sure the instantaneous dipole is just the electron shells wobbling creating slightly positive and negative sides.


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    (Original post by Desiboi101)
    Van der waals forces consist of 3 intermolecular forces: hydrogen bonding, LDF and PD/PD interactions.

    The understanding you have of LDF is correct, so that's alright for now.

    A PD/PD occurs when there is a difference in electronegativity in a molecule. Remember electronegativity is a measure of the strength of attraction an atom has for its shared electrons in a bond. So if you take a molecule with a large difference in negativity, the electrons will be pulled towards the more electronegative atom. This is because it is smaller and the strength of attraction operates over a smaller distance than it does in a larger one. So this results in a permanent dipole since the electrons are pulled towards one side of the molecule, creating a slightly negative charge. In contrast, on the opposite side of the molecule the deficiency in electrons (due to them being pulled towards the more electronegative side) will result in a slightly posture charge.

    An induced dipole is basically when a other dipole (temporary if I remember back correctly) is formed due to close contact with a temporary dipole, where the slightly negative side of the temporary dipole repels the electrons of the other atom. On the other side of the induced atom, the deficiency of electrons results in a slightly positive charge. So they are therefore held by LDF in this way.

    I'm pretty sure the instantaneous dipole is just the electron shells wobbling creating slightly positive and negative sides.


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