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    (Original post by O9tharakanc)
    Same
    woooo science club
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    I'm so silly, I've figured it out, I was being daft..
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    (Original post by O9tharakanc)
    Im Doing aqa as well unit 1 is okay unit 2 looks hard
    People in the year above said they did not have much time to revise unit 2. As a result, most people did better in unit 1 but really badly in unit 2. We did a bit of unit 2 before the holidays and it was undoubtedly difficult to understand. Also the ISAs are horrible with their monstrous grade boundaries. Which the the result of some schools cheating on them.
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    E.g KNO3 This is potassium nitrate, but in order to be complete we need to get systematic name we need the oxidation of nitrogen. We know that K forms +1 ions, so charge on the nitrate ion must be (-2*3) -6. The book says that that know the oxidation number of the overall ion is -1. How do we know it's -1 I would have assumed it would have been 0. Can someone please help me out, I'm quite confused.

    Also in Cu2O How am I supposed to know that when we find the systematic name of it we need to find the oxidation of Copper in this example. Why are we not finding the oxidation state of oxygen?
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    (Original post by GoldGhost)
    E.g KNO3 This is potassium nitrate, but in order to be complete we need to get systematic name we need the oxidation of nitrogen. We know that K forms +1 ions, so charge on the nitrate ion must be (-2*3) -6. The book says that that know the oxidation number of the overall ion is -1. How do we know it's -1 I would have assumed it would have been 0. Can someone please help me out, I'm quite confused.
    Hmm I'm not sure how the ion matters.

    K = +1
    O = -2
    N = n (I'm doing it algebraically!)

    1 + n + 3(-2) = 0

    Equals zero because the compound overall has no charge.

    1 + n – 6 = 0
    n = 5

    Potassium nitrate(V)

    SECOND METHOD:

    NO3- Nitrate ion has a charge of -1 so oxidation numbers add together to make -1.

    O = -2
    N = n

    n + 3(-2) = -1
    n – 6 = -1
    n = 5

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    (Original post by GoldGhost)
    E.g KNO3 This is potassium nitrate, but in order to be complete we need to get systematic name we need the oxidation of nitrogen. We know that K forms +1 ions, so charge on the nitrate ion must be (-2*3) -6. The book says that that know the oxidation number of the overall ion is -1. How do we know it's -1 I would have assumed it would have been 0. Can someone please help me out, I'm quite confused.
    If K has +1, NO3 must have what to make the compound overall 0?

    Remember also oxygen has a nearly permanent oxidation state of -2
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    (Original post by GoldGhost)
    E.g KNO3
    Also in Cu2O How am I supposed to know that when we find the systematic name of it we need to find the oxidation of Copper in this example. Why are we not finding the oxidation state of oxygen?
    Oxygen nearly never changes (you can say it's -2 pretty much all the time- it certainly doesn't change enough that it warrants an oxidation state in its systematic name) Copper is a transition metal, meaning its oxidation state changes loads. Generally if you have a transition metal, that's the most important thing to give the oxidation number of.


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    (Original post by danconway)
    Oxygen nearly never changes (you can say it's -2 pretty much all the time- it certainly doesn't change enough that it warrants an oxidation state in its systematic name) Copper is a transition metal, meaning its oxidation state changes loads. Generally if you have a transition metal, that's the most important thing to give the oxidation number of.


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    Thank-you danconway and Dylann, I understand it now!
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    Thought I'd pop in and say hello. I am current year 12 (though never post on the thread bc I never find the time ) and studying OCR A chemistry (alongside CCEA maths, biology and French- so glad I'm on an English board for chem!).
    I'm actually not finding it too difficult at the moment, though nomenclature has taken a fair while to get used to! I've started the old foundation past papers which are equivalent to F321 and they're fairly straightforward, though I suspect F322 will be another story!
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    (Original post by danconway)


    The Avogadro Constant (NA) is number of particles of a substance (atoms, molecules, ions) in one mole of the substance.

    So, first, you need to work out how many moles of water there are, and then multiply that by NA for the number of molecules of water (because you used the number of moles of H2O, which is a molecule, you'll get the number of molecules out).

    Then have a think about how you get from molecules to atoms.
    Thanks a lot
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    (Original post by BCMFM16)
    People in the year above said they did not have much time to revise unit 2. As a result, most people did better in unit 1 but really badly in unit 2. We did a bit of unit 2 before the holidays and it was undoubtedly difficult to understand. Also the ISAs are horrible with their monstrous grade boundaries. Which the the result of some schools cheating on them.
    Yeah I knowing heard unit 2 is quite difficult to understand I might look over it . I'm doing empa's which are simmilar to Isa's but they are externally marked so lower grade boundaries but are difficult as you get o help From teachers have you done any praticals
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    (Original post by Isabella~)
    Hiya, I'm doing OCR B
    I did ocr b. They say it's the hardest exam board for chem

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    (Original post by O9tharakanc)
    Yeah I knowing heard unit 2 is quite difficult to understand I might look over it . I'm doing empa's which are simmilar to Isa's but they are externally marked so lower grade boundaries but are difficult as you get o help From teachers have you done any praticals
    Oh I see...I think my school just chose ISAs as they are easier to deal with.
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    Can somebody please explain to me about reacting an acid and a base.
    So the general formula is
    Acid + base --> salt + water

    E.g HCl with calcium oxide as the base
    So hydrochloric acid + calcium oxide --> calcium chloride + water
    Same as - 2HCl + CaO --> CaCl2 + H2O

    Does the HCl release it's H+ ions and the H+ cannot be in water as H+ so it has to bond with water to, H3O+. Then We have the Cl and the Calcium which bond together and form CaCl2... is this correct?
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    (Original post by Dinaa)
    Hello AS Chemistry TSRians!

    I thought it would be a good idea to make a thread, where students doing AS Chemistry, post/ask questions, and we could all help each other out?

    Teaching another person, also helps you become more confident and you both develop a better understanding. I know there is an A-level chat thread already, but this should be for learning!

    There is no such thing as a silly question, so ask away and hopefully, you'll find someone who can help you

    I shall also make a list of the Chemistry students, and what exam board they're all on! So please post what exam board you are on, if you are in!

    List of the students doing Chemistry!

    Spoiler:
    Show





































    Lovely helpers!

    Spoiler:
    Show







    I apologize if I've missed anyone out, got the list from Current year 12 list! (Lazy i know) :mmm:

    P.S- If you don't want to, okay, you are not obliged to do so! But please, no rude/offensive comments

    :elefant::elefant::elefant::elefant::elefant::elefant::elefant::elefant::elefant::elefant:
    I'm doing AQA.
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    heya.i am doing ocr AS
    chem. i am doing both unit 1 and unit 2
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    Hi has anyone already done their AS mocks? I have my unit 1 mock the week after christmas (next week :yikes::yikes::work: )
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    (Original post by GoldGhost)
    Can somebody please explain to me about reacting an acid and a base.
    So the general formula is
    Acid + base --> salt + water

    E.g HCl with calcium oxide as the base
    So hydrochloric acid + calcium oxide --> calcium chloride + water
    Same as - 2HCl + CaO --> CaCl2 + H2O

    Does the HCl release it's H+ ions and the H+ cannot be in water as H+ so it has to bond with water to, H3O+. Then We have the Cl and the Calcium which bond together and form CaCl2... is this correct?
    Yeah It's correct but the formula for water is H2O :yep:

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    (Original post by diana99)
    Yeah It's correct but the formula for water is H2O :yep:

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    I know :P but I thought H2O + H+ --> H3O+ ? Unless I am mistaken
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    (Original post by GoldGhost)
    I know :P but I thought H2O + H+ --> H3O+ ? Unless I am mistaken
    Sorry it's just my opinion. I could be wrong however.

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