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OCR chemistry unit 1 Friday 21st May 2010 watch

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    (Original post by ThisIsAbsolution)
    Anyone doing Salters OCR B tomorrow?
    I am

    Do you know where i can get the Jan 2010 paper?
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    (Original post by Najmin_Akhtar)
    I am

    Do you know where i can get the Jan 2010 paper?
    Unfortunately not, they have the examiners report up for it, but not the actual paper =/

    Im hoping tomorrow will be nice, apprently Jan 10's grade boundary for an A was 41/60, while being relatively ok
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    (Original post by Jaspreet92)
    Can you explain this please? This is one of the things that I don't get.
    Across a period, proton number increas, and nuclear charge increases so outer electron is drawn to the nucleus more. Atomic radius decreases for this reason also, because out electron is drawn to nucleus. There is very little/ no shiedling. Also, ionic size decreases as you go across the period.
    Therefore first ionisation energy (I.E.) increases, as its harder to remove the electron.

    Down the period, atomic radii increases, as a new shell has been added on, so shielding also increases, as electron is further away from the nucleus so nuclear attraction decreases. Even though there is more protons, it is cancelled out by the resulting less attraction by atomic radii and electron shielding. Therefore first I.E. decreases, and yo can link this into group 2 metals getting more reactive down the period when they want to give up 2 out electrons in the S- sub shell config.

    When talking about melting and boiling points across the period, you must refer to the structures and types of forces and bonding between the elements.
    So looking at period 2 and 3 it goes like this
    Li, Be, Na, Mg and Al :
    • Giant metallic structures,
    • with electrostatic attraction between positive ions and delocalised electrons, which are very strong. [High melting and boiling point]
    •These elements are involved in metallic bonding.

    B, C, Si :
    • Giant covalent structures,
    •a shared pair of electrons between two molecules. There are lots of them, and they are very very strong, and require a lot of energy to break. [High melting and boiling point]
    •These elements are involved in covalent bonding.

    N2, O2, F2, Ne, P4, S8, Cl2, Ar :
    • Simple molecular structure
    • Not very strong, have van der waals forces between them, which do not require a lot of energy to overcome/break and therefore have a relatively low melting and boiling point.
    •Van der Waals forces are used for bonding.

    Hope this helps. If anyone has any more questions, please do ask
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    (Original post by hardz21)
    Across a period, proton number increas, and nuclear charge increases so outer electron is drawn to the nucleus more. Atomic radius increases for this reason also, because out electron is drawn to nucleus. There is very little/ no shiedling. Also, ionic size decreases as you go across the period.
    Therefore first ionisation energy (I.E.) increases, as its harder to remove the electron.

    Down the period, atomic radii increases, as a new shell has been added on, so shielding also increases, as electron is further away from the nucleus so nuclear attraction decreases. Even though there is more protons, it is cancelled out by the resulting less attraction by atomic radii and electron shielding. Therefore first I.E. decreases, and yo can link this into group 2 metals getting more reactive down the period when they want to give up 2 out electrons in the S- sub shell config.

    When talking about melting and boiling points across the period, you must refer to the structures and types of forces and bonding between the elements.
    So looking at period 2 and 3 it goes like this
    Li, Be, Na, Mg and Al :
    • Giant metallic structures,
    • with electrostatic attraction between positive ions and delocalised electrons, which are very strong. [High melting and boiling point]
    •These elements are involved in metallic bonding.

    B, C, Si :
    • Giant covalent structures,
    •a shared pair of electrons between two molecules. There are lots of them, and they are very very strong, and require a lot of energy to break. [High melting and boiling point]
    •These elements are involved in covalent bonding.

    N2, O2, F2, Ne, P4, S8, Cl2, Ar :
    • Simple molecular structure
    • Not very strong, have van der waals forces between them, which do not require a lot of energy to overcome/break and therefore have a relatively low melting and boiling point.
    •Van der Waals forces are used for bonding.

    Hope this helps. If anyone has any more questions, please do ask
    heyy buddy lol
    you are going to do soo well i can imagine you 2moro on here saying 'man that was some easy paper' and i'll be like 'noo i flopped' lmao

    good luck!
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    lol guys unit 2 is the hardest paper, concentrate on that
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    Hey! Just did the 2010 Jan paper as a quick last min test.. Think I'm ready.. Can anyone please let me know where I can find the MS? It's really irritating how my college VLE has the QP but not the MS..And just thought you'd like to know, it was 46/60 (raw marks) to get an A in Jan '10.. :-) Hope it's the same this May!!

    Thanks
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    (Original post by J DOT A)
    lol guys unit 2 is the hardest paper, concentrate on that
    I wouldn't say that.. Unit four is freakin' hard.. Unit 5's alright though :-)
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    ok im going to post some stuff for my own sake and everyone elses you dont have to read it but like it will benefit you

    i predict that they will ask for the definition of a MOLE as it hasnt been asked in the past 3 papers.

    so a mole: amount of any substance that contains as many particles as there are carbon atoms in 12g of the c-12 isotope.


    ohh actually can someone help me with the following:

    why is GRAPHITE is INSOLUBLE?
    AND WHY SODIUM CHLORIDE IS SOLUBLE?

    and...
    what happens when u react CaCO3 with HCl
    and CaO with HCl
    and what would the OBSERVATIONS be for both?
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    (Original post by J DOT A)
    lol guys unit 2 is the hardest paper, concentrate on that
    we got agess for that lool might aswell get the easy stuff right
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    (Original post by 786girl)
    we got agess for that lool might aswell get the easy stuff right
    We have 18 days man thats gonna come so quick, I'm so stressed out right now
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    (Original post by J DOT A)
    We have 18 days man thats gonna come so quick, I'm so stressed out right now
    it'll be fine!! if u do half a topic a day u got plenty of timee dont worryyyyy
    im stressed out too i havent done ANY biology revison which is on tuesday :eek3:
    i just hateee unit 1 its so retarded.
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    (Original post by 786girl)
    it'll be fine!! if u do half a topic a day u got plenty of timee dont worryyyyy
    im stressed out too i havent done ANY biology revison which is on tuesday :eek3:
    i just hateee unit 1 its so retarded.
    Oh unit 1 OCR for Bio? LOL make sure you know what potometers are... and the lymphatic system hint hint.

    yeah Unit 2 is coming up as well and theres so much **** I cant bare it.
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    (Original post by J DOT A)
    Oh unit 1 OCR for Bio? LOL make sure you know what potometers are... and the lymphatic system hint hint.

    yeah Unit 2 is coming up as well and theres so much **** I cant bare it.

    lol wot do you meannnn hint hint
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    (Original post by ThisIsAbsolution)
    Anyone doing Salters OCR B tomorrow?
    Yah, I am.
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    (Original post by 786girl)
    ok im going to post some stuff for my own sake and everyone elses you dont have to read it but like it will benefit you

    i predict that they will ask for the definition of a MOLE as it hasnt been asked in the past 3 papers.

    so a mole: amount of any substance that contains as many particles as there are carbon atoms in 12g of the c-12 isotope.


    ohh actually can someone help me with the following:

    why is GRAPHITE is INSOLUBLE?
    AND WHY SODIUM CHLORIDE IS SOLUBLE?

    and...
    what happens when u react CaCO3 with HCl
    and CaO with HCl
    and what would the OBSERVATIONS be for both?
    Hey, thanks for that other comment dude. Hope your okay. And naaah, im stressing out like bare, nerves are getting to me. Hope everyone does well though !!!!

    btw, graphite is insoluble because is is a giant covalent molecule so it can't let polar or non-polar moelcules/solvents break the reallllly strong covalent bonds. Sodium chloride is soluble because the ionic compound dissolves in polar molecules like water, so basically the Na+ attracts the delta negative charges on the Oxygen of H2O and the Cl- attracts the delta positive charge on the hydrogen molecule.

    Remember, carbonate + acid -> salt + watet + carbon dioxide

    so, CaCO3 (s) + 2HNO3 (aq) -> Ca(NO3)2 (aq) + H2O (l) + CO2 (g)
    Here the solid [CaCO3] dissappears, and it effervesses-because CO2 gas is produced

    CaO (s) + 2HCl (aq) -> CaCl2 (aq) + H2O (l)
    Here the CaO [calcium oxide] is a solid, and as it reacts it disappears

    Hope this helps, good luck mate.
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    (Original post by 786girl)


    ohh actually can someone help me with the following:

    why is GRAPHITE is INSOLUBLE?
    AND WHY SODIUM CHLORIDE IS SOLUBLE?

    and...
    what happens when u react CaCO3 with HCl
    and CaO with HCl
    and what would the OBSERVATIONS be for both?
    Hello!

    - Graphite's insoluble because it's formed in a covalent lattice (carbon) - the covalent bonds in the sheets of carbon are too difficult to break. This means it can't be dissolved in ANY solvent. Same with diamond.

    - Sodium chloride has a giant IONIC lattice. Due to water (or the solvent) being polar, the water molecules pull the ions away from the lattice - therefore dissolving sodium chloride.
    This is because the hydrogen in the water molecules has a slightly positive charge, and the oxygen has a slightly negative charge. They respectively surround the positive and negative ions in sodium chloride (Na+ & Cl-).

    Next,

    These are less likely to come up, but:

    - When you react CaCO3 with HCl you get this equation:

    CaCO3(s) + 2HCL(aq) ---> CaCl2(aq) + CO2(g) + H2O(l)

    In terms of observations, you would SEE effervescence as the carbon dioxide is produced - I think that's all you need to know.

    - When you react CaO with HCl you get this equation:

    CaO(s) + 2HCL(aq) ---> CaCL2(aq) + H2O(l)

    In terms of what you'd see. Uhh... You'd see a white crystalline solid (CaO) dissolve.

    I've probably got that all wrong but hey!

    Good luck
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    ... So not only does somebody answer your question in the time that I took writing it. But they explained it better than me!

    Fml. Trying to do a nice thing. Haha, well done hardz21

    Questionable name... *cough*.
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    (Original post by hardz21)
    Across a period, proton number increas, and nuclear charge increases so outer electron is drawn to the nucleus more. Atomic radius increases for this reason also, because out electron is drawn to nucleus. There is very little/ no shiedling. Also, ionic size decreases as you go across the period.
    Therefore first ionisation energy (I.E.) increases, as its harder to remove the electron.

    Down the period, atomic radii increases, as a new shell has been added on, so shielding also increases, as electron is further away from the nucleus so nuclear attraction decreases. Even though there is more protons, it is cancelled out by the resulting less attraction by atomic radii and electron shielding. Therefore first I.E. decreases, and yo can link this into group 2 metals getting more reactive down the period when they want to give up 2 out electrons in the S- sub shell config.

    When talking about melting and boiling points across the period, you must refer to the structures and types of forces and bonding between the elements.
    So looking at period 2 and 3 it goes like this
    Li, Be, Na, Mg and Al :
    • Giant metallic structures,
    • with electrostatic attraction between positive ions and delocalised electrons, which are very strong. [High melting and boiling point]
    •These elements are involved in metallic bonding.

    B, C, Si :
    • Giant covalent structures,
    •a shared pair of electrons between two molecules. There are lots of them, and they are very very strong, and require a lot of energy to break. [High melting and boiling point]
    •These elements are involved in covalent bonding.

    N2, O2, F2, Ne, P4, S8, Cl2, Ar :
    • Simple molecular structure
    • Not very strong, have van der waals forces between them, which do not require a lot of energy to overcome/break and therefore have a relatively low melting and boiling point.
    •Van der Waals forces are used for bonding.

    Hope this helps. If anyone has any more questions, please do ask
    I thought the atomic radius decreases?
    Sorry if i'm mistaken. All this revision is just confusing me more and more
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    (Original post by Minusthevolta)
    ... So not only does somebody answer your question in the time that I took writing it. But they explained it better than me!

    Fml. Trying to do a nice thing. Haha, well done hardz21

    Questionable name... *cough*.
    noo i read yours aswell and hey it helped you recall stuff for your own help lol
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    (Original post by Hoomz)
    I thought the atomic radius decreases?
    Sorry if i'm mistaken. All this revision is just confusing me more and more
    No no, you're right, i think i got overwhelmed and made a mistake. thanks for correcting me !!! And good luck. Ive just finished looking over the unit, time to do some more past exam papers and definitions

    good luck and thanks, that revision is paying off
 
 
 
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