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    (Original post by Terrydaktal)
    Define electrolysis (2 marks)

    -Separation of an ionic compound into its comprising elements
    -Using electricity

    You may be given copper carbonate - copper has a +2 charge and carbonate ion has a -2 charge, this is depicted on the reactivity series handout.

    The Copper carbonate needs to be in a solution form in order for electrolysis to occur as ions can move
    Metals are generally melted into molten form so that ions can move and a flow of charge can transpire

    the positive ions form at the negative electrode
    the negative ions - carbonate (-2) form at the positive

    think like charges attract,

    this is because the negative electrode wants to give the positive ion an electron so that it becomes the original Cu - copper metal from the copper ion by gaining 2 electrons. it becomes reduced.
    the positive electrode wants to take away electrons from the negative ion, the negative ion becomes oxidised

    at the negative electrode the metal will be produced if it is less reactive than hydrogen hydrogen will be produced if the metal is more reactive than hydrogen, you can see this by looking at the reactivity series

    as copper is less reactive than hydrogen , copper is formed

    the equations are easy to balance and complete, they will ask you to complete ___
    O2- → O2 + ____
    it would need to be 2 O2- this is beacuse there is 2 oxygens on the other side so there needs to be 2 oxygens on this side

    on the right i would need to be e- to represent the electrons lost by the oxygen ion, the number would need to be "4e-" due to the fact that there are 2 electons needed to be lost by each oxygen oxygen ion so it becomes O, there are 2 Oxygens due to "2O2-" which means that there are 4 electrons as 2x2 = 4

    btw, with cryolite,

    Cryolite is used in the electrolysis of aluminium because

    -it reduces the melting point of aluminium
    -meaning that less temperature is required to melt it so it is molten and the ions can move
    -less energy required as less temperature is needed to melt aluminium
    -reducing energy costs

    if the electrodes are carbon just remember that carbon electrodes react with oxygen, if oxygen is being formed at an electrode that is fabricated with carbon then the oxygen will react with the carbon and it will form CO2 and the electrode will slowly vanish c;
    Sorry, but can you please further explain the formula where you had the answer of 4e-.

    Thanks
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    (Original post by AgonizedGod)
    Sorry, but can you please further explain the formula where you had the answer of 4e-.

    Thanks
    yeah i found that hard. are you ok with empirical formula or working out the highest theoretical mass gain of a substance?

    ok.

    so if something is + then it must gain an electron because electrons are negative 1+ (-1) = 0 , so it can become the original metal.

    2H+ + 2e- → H2

    think of it as
    H+ + e- → H

    hydrogen ion which is positive plus an electron goes to normal hydrogen "H", but because they have given you "H2 " instead which is 2 hydrogens you must balance the equation so that there is an equal amount of hydrogen on each side

    H+ + e- → H2 - you cant just leave it like this as the ratio is unbalanced
    1 : 2
    so you need to put a 2 infront of the hydrogen ion so that it becomes

    2H+ + e- → H2
    2 : 2

    but as each hydrogen ion gains one electron and you have now made it 2H+ so that there are now 2 hydrogen ions it means that 2 hydrogen ions take 2 electrons as one hydrogen ion takes one electron etc

    so you make it

    2H+ + 2e- → H2
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    (Original post by Terrydaktal)
    yeah i found that hard. are you ok with empirical formula or working out the highest theoretical mass gain of a substance?

    ok.

    so if something is + then it must gain an electron because electrons are negative 1+ (-1) = 0 , so it can become the original metal.

    2H+ + 2e- → H2

    think of it as
    H+ + e- → H

    hydrogen ion which is positive plus an electron goes to normal hydrogen "H", but because they have given you "H2 " instead which is 2 hydrogens you must balance the equation so that there is an equal amount of hydrogen on each side

    H+ + e- → H2 - you cant just leave it like this as the ratio is unbalanced
    1 : 2
    so you need to put a 2 infront of the hydrogen ion so that it becomes

    2H+ + e- → H2
    2 : 2

    but as each hydrogen ion gains one electron and you have now made it 2H+ so that there are now 2 hydrogen ions it means that 2 hydrogen ions take 2 electrons as one hydrogen ion takes one electron etc

    so you make it

    2H+ + 2e- → H2
    Thank you so much for that and good luck for tomorrow.
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    I think the unit 3 paper will be based upon the advantages and disadvantages of Hard water for the 6 mark
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    Can someone explain reacting mass equations for me? im finding it so difficult to understand
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    (Original post by Terrydaktal)
    yeah, i sat down at a desk and did all 10 past papers today, back to 2008 :> chaos. Every time the question comes up:

    which of these questions cannot be answered by science alone, explain why

    *tick the appropriate box*

    why: it is based on opinion
    it is an economic/ethical/environmental issue

    also a question on why CO2 has a low boiling point:

    -it is simple molecular
    -there are weak intermolecular forces between the molecules
    -little energy is required to break the bonds
    -meaning that a low temperature will cause it to boil

    or on the structure of graphite

    -made of layers
    -layers have weak bonds between them
    -meaning that the layers can slide over each-other.
    -meaning that graphite is soft or malleable.

    or on diamond

    -strongly covalently bonded to 4 other carbon atoms
    -it is a giant covalent structure
    -the structure is very rigid as there are no layers that can slide over each-other
    -high melting point

    or on thermosoftening / setting polymers

    -thermosoftening polymers do not have crosslinks between the chains of monomers
    -meaning that they can melt and the structure warps

    or why to close the lid on chromatography

    -prevent solvent from vaporating

    or why not to use pen to mark the chromatography paper

    -ink dissolves into solvent
    -smudges and runs up the page
    -affecting experiment

    -
    This is super helpful!! Thanks
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    I literally am sat here staring at the 'salts,acids and base' revision page. I literally don't get it. Hope the 6 mark isn't on this or I'm dead :confused:
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    (Original post by SharDee)
    I literally am sat here staring at the 'salts,acids and base' revision page. I literally don't get it. Hope the 6 mark isn't on this or I'm dead :confused:
    the main thing I got from that was..
    hydrogen - makes the solution acidic
    hydroxide - makes the solution alkaline

    if you're struggling, I would say these are easy points to remember on that:crossedf::crossedf:
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    I quote my teacher today...'the exam is going to be a *****' so I don't feel very confident! Especially after biology!

    Chemistry and biology are my favourite subjects so I really want to do well.

    For electrolysis, how many examples have I learnt? I've learnt lead bromide, brine and aluminium oxide...?
    Good luck to you all tomorrow


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    (Original post by TahmidGCSE)
    I think the unit 3 paper will be based upon the advantages and disadvantages of Hard water for the 6 mark
    Hope so! There's easily enough to say about that:

    Advantages
    – Stronger teeth/bones
    – May reduce risks of heart disease
    – Some people say it tastes better

    Disadvantages
    - forms scale + explain how - this reduces efficiency of electrical appliances such as kettles
    - forms soap scum + explain how - wastes soap

    Anything else anyone can think of??
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    (Original post by Terrydaktal)
    yeah, i sat down at a desk and did all 10 past papers today, back to 2008 :> chaos. Every time the question comes up:

    which of these questions cannot be answered by science alone, explain why

    *tick the appropriate box*

    why: it is based on opinion
    it is an economic/ethical/environmental issue

    also a question on why CO2 has a low boiling point:

    -it is simple molecular
    -there are weak intermolecular forces between the molecules
    -little energy is required to break the bonds
    -meaning that a low temperature will cause it to boil

    or on the structure of graphite

    -made of layers
    -layers have weak bonds between them
    -meaning that the layers can slide over each-other.
    -meaning that graphite is soft or malleable.

    or on diamond

    -strongly covalently bonded to 4 other carbon atoms
    -it is a giant covalent structure
    -the structure is very rigid as there are no layers that can slide over each-other
    -high melting point

    or on thermosoftening / setting polymers

    -thermosoftening polymers do not have crosslinks between the chains of monomers
    -meaning that they can melt and the structure warps

    or why to close the lid on chromatography

    -prevent solvent from vaporating

    or why not to use pen to mark the chromatography paper

    -ink dissolves into solvent
    -smudges and runs up the page
    -affecting experiment

    -
    I can't give you a rep for each of your comments BUT all your answers are EXTREMELY helpful!! thank you so much!
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    (Original post by #sarahsmith2)
    Hope so! There's easily enough to say about that:

    Advantages
    – Stronger teeth/bones
    – May reduce risks of heart disease
    – Some people say it tastes better

    Disadvantages
    - forms scale + explain how - this reduces efficiency of electrical appliances such as kettles
    - forms soap scum + explain how - wastes soap

    Anything else anyone can think of??
    Disadvantage:

    it's more expensive as more soap is needed to form lather.
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    (Original post by SuperHuman98)
    Can someone explain reacting mass equations for me? im finding it so difficult to understand
    Okay an example question:
    What mass of carbon dioxide is formed when 12 g of carbon is burned in air?

    1) Write out a balanced equation for the reaction

    C + O2 -> CO2

    2) Work out which two are involved in the calculation (it will be the mass you are given and then the mass you need to work out)

    Our teacher makes us write it out like this to make it easier

    .....................C.......... +.........O2.........->........CO2
    Moles...........1............... ................................ ....1
    Mass...........12............... ................................ ..?
    RFM ...........12 ................................ ...............44

    (sorry about the dots it wouldn't let me do it like this without them!)

    3) Fill in the table above with what you know... RFM can be calculated from the data sheet.

    4) Using the formula moles = mass/RFM work out the moles for carbon - in this case it is 1 as 12/12 = 1

    5) You can work out the molar ratio by using the big numbers in front of the compounds - as neither C nor CO2 has a number in front this is a 1:1 ratio... so there is 1 mole of CO2 also

    6) Finally using the equation mass = moles x RFM... you can work out the mass of CO2 produced is 44g
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    (Original post by #sarahsmith2)
    Hope so! There's easily enough to say about that:

    Advantages
    – Stronger teeth/bones
    – May reduce risks of heart disease
    – Some people say it tastes better

    Disadvantages
    - forms scale + explain how - this reduces efficiency of electrical appliances such as kettles
    - forms soap scum + explain how - wastes soap

    Anything else anyone can think of??
    Then again I think they will have another experiment question last 2 years were methods so they might have a flame test as the 6 mark question just my theory...
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    (Original post by AgonizedGod)
    Thank you so much for that and good luck for tomorrow.
    ty c:
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    (Original post by Lucykx)
    This is super helpful!! Thanks
    i meant evaporating not vaporating
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    does anyone have any easy tips to remember how to make salts? I can remember that most chlorides, sulfates and nitrates are soluble, and most oxides and hydroxides are insoluble. But can someone help with the ways you make soluble and insoluble salts? e.g. precipitation, using alkalis, using metals
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    (Original post by Terrydaktal)

    also a question on why CO2 has a low boiling point:

    -it is simple molecular
    -there are weak intermolecular forces between the molecules
    -little energy is required to break the bonds
    -meaning that a low temperature will cause it to boil


    -
    I thought the Intermolecular forces were broken not the bonds. The Covalent bonds are very difficult to overcome?
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    (Original post by ajbrown27)
    does anyone have any easy tips to remember how to make salts? I can remember that most chlorides, sulfates and nitrates are soluble, and most oxides and hydroxides are insoluble. But can someone help with the ways you make soluble and insoluble salts? e.g. precipitation, using alkalis, using metals
    acid + metal oxide → salt + water
    acid + metal hydroxide → salt + water
    acid + reactive metal → salt + hydrogen
    acid + base
    salt + water
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    What would the six mark question on salts be? Like I get that bit, but I don't know if I'd be able to answer a 6 mark question on it
 
 
 
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