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    (Original post by haj101)
    You need to be able to identify the metal and non metal elements in the periodic table,
    Ionic- non-metal and metal
    Covalent- both non metals
    Dative- if the shared pair of electrons come from the same atom

    Strontium chloride- strontium is metal and chlorine is non-metal therefore it is ionic
    thank you so much
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    (Original post by haj101)
    You need to be able to identify the metal and non metal elements in the periodic table,
    Ionic- non-metal and metal
    Covalent- both non metals
    Dative- if the shared pair of electrons come from the same atom

    Strontium chloride- strontium is metal and chlorine is non-metal therefore it is ionic
    Well I mean, that is a sort of rule of thumb, but it's not true of course.
    Ionic bonds can form between two non metals, and covalency exists within bonds that theoretically are ionic.
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    (Original post by Cobalt_)
    Hi people, Chemistry student at University here.
    Got an A* in alevel so if anyone has any questions or whatever, feel free to ask them.


    Love to help
    Hey, congrats on the A*, I would like to ask, whats the best way to revise for chemistry.
    I havent started yet and i am about 30 days from from first exams, could you suggest something.
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    (Original post by Science_help)
    Hey, congrats on the A*, I would like to ask, whats the best way to revise for chemistry.
    I havent started yet and i am about 30 days from from first exams, could you suggest something.
    Well I had the old spec so my advice may be a bit out dated.

    I just tbh revised my notes for around a week. I would read them, then write them back after a few hours to make sure I really learnt them.

    Then I would do all the past papers, including every single old spec paper. From 2000-2013.

    Thats honestly the best advice I can give sorry, I know its really short but honestly thats it. Make sure you know the material and practice exam style questions, if you can do that you will get an A* no problem.

    One tip: Chemistry isnt biology. Memorising the content wont get you far, you did to really understand everything you're learning and dont just simply remember it. Exam boards test chemistry has a subject where you apply your knowledge and if you're simply just remembering things you wont be able to apply it to new situations.
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    (Original post by Cobalt_)
    Well I had the old spec so my advice may be a bit out dated.

    I just tbh revised my notes for around a week. I would read them, then write them back after a few hours to make sure I really learnt them.

    Then I would do all the past papers, including every single old spec paper. From 2000-2013.

    Thats honestly the best advice I can give sorry, I know its really short but honestly thats it. Make sure you know the material and practice exam style questions, if you can do that you will get an A* no problem.

    One tip: Chemistry isnt biology. Memorising the content wont get you far, you did to really understand everything you're learning and dont just simply remember it. Exam boards test chemistry has a subject where you apply your knowledge and if you're simply just remembering things you wont be able to apply it to new situations.
    Thank you for this soo much
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    (Original post by Science_help)
    Thank you for this soo much
    Np, just put the work in and you'll get your A*.

    If I got an A*, anyone can.
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    (Original post by Cobalt_)
    Np, just put the work in and you'll get your A*.

    If I got an A*, anyone can.
    well i am currenlty in year 12, so only can get an A, but all year ive been geting around 90-95%, and so i really want atleast 95% ums in chem AS
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    Help please.
    Q)... prepares 250cm3 of a 0.0800moldm-3 a solution of borax water, calculate the mass of borax (Na2B4O7.10H2O) to make this solution
    A) Molar mass of borax = 381.2 (g mol–1) 
    Correctly calculates the mass of borax in 1000 cm3 =0.0800 x 381.2= 30.496 g OR 30.50 g OR 30.5g
    Correctly calculates the mass of borax in 250 cm3 =30.496/4= 7.624 g OR 7.62 g

    How do you know it's 1000 cm3?
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    can someone explain something to me..
    In the titration where you add potassium manganate(VII) to an unknown conc of a reducing agent (e.g. iron, zinc, or Fe2+)
    why is the end point of the reaction indicated by a colour change of colourless to pink?
    Surely if you're adding manganate (VII) ions to Fe2+ ions, it will be reduced to Mn2+.. which is colourless?
    Why do you get a purple colour in the conical flask?
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    (Original post by RMNDK)
    There are some mistakes in your equation of Co2+ with NH3.
    You also might want to give the colour of [Co(H2O)6]2+ before it is oxidised by oxygen.

    How come you haven't included the equation of Fe3+ with excess OH- ?
    The precipitate will dissolve in concentrated NaOH.
    I'll relook through it, sorry about the mistakes. I will repost the altered version
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    (Original post by chzm)
    can someone explain something to me..
    In the titration where you add potassium manganate(VII) to an unknown conc of a reducing agent (e.g. iron, zinc, or Fe2+)
    why is the end point of the reaction indicated by a colour change of colourless to pink?
    Surely if you're adding manganate (VII) ions to Fe2+ ions, it will be reduced to Mn2+.. which is colourless?
    Why do you get a purple colour in the conical flask?

    I wouldn't say purple, the end-point is the first hint of a pink tinge colour.

    The reason why it's colourless to pink is because exactly what you said.
    If you add Mn7+ to Fe2+, they will be reduced to Mn2+ which is colourless.

    As I keep adding and adding the Mn7+, all the Fe2+ will eventually become oxidised to Fe3+.

    There is a single moment when I have fully oxidised all the Fe2+ in the conical flask, and so at that moment, there is no more Fe2+.

    Thus, the instant I add more Mn7+, it's going to remain as Mn7+ because there's nothing to oxidise. Thus we get this pink tinge colour. Add some more and we get that intense purple colour.

    Unless you wanted to use some sort of indicator which changes colour around the neutralisation point, you would look for this colour change. And we tend not to because it is a prominent change.
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    (Original post by chzm)
    can someone explain something to me..
    In the titration where you add potassium manganate(VII) to an unknown conc of a reducing agent (e.g. iron, zinc, or Fe2+)
    why is the end point of the reaction indicated by a colour change of colourless to pink?
    Surely if you're adding manganate (VII) ions to Fe2+ ions, it will be reduced to Mn2+.. which is colourless?
    Why do you get a purple colour in the conical flask?
    Because the Fe2+ ions have been used up at the end point, so there are some purple Mn7+ ions which can't be oxidised to colourless Mn2+ ions so the solution turns pink
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    (Original post by LThomas694)
    Because the Fe2+ ions have been used up at the end point, so there are some purple Mn7+ ions which can't be reduced to colourless Mn2+ ions so the solution turns pink
    OILRIG
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    (Original post by TeachChemistry)
    OILRIG
    Sorry if I've messed something up there but I swear that's right? In the overall redox equation:
    MnO4- + 8H+ + 5Fe2+ --> Mn2+ + 5Fe3+ + 4H2O
    Mn7+ ions are reduced to Mn2+ because reduction is a gain of electrons and a decrease in oxidation number, and Fe2+ ions are oxidised to Fe3+ ions because oxidation is a loss of electrons and an increase in oxidation number?
    At the end point all of the Fe2+ ions have been oxidised to Fe3+ so there aren't any Fe2+ ions left to reduce the Mn7+ ions to Mn2+ so the solution turns pink since Mn7+ ions are purple?
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    (Original post by LThomas694)
    Sorry if I've messed something up there but I swear that's right? In the overall redox equation:
    MnO4- + 8H+ + 5Fe2+ --> Mn2+ + 5Fe3+ + 4H2O
    Mn7+ ions are reduced to Mn2+ because reduction is a gain of electrons and a decrease in oxidation number, and Fe2+ ions are oxidised to Fe3+ ions because oxidation is a loss of electrons and an increase in oxidation number?
    At the end point all of the Fe2+ ions have been oxidised to Fe3+ so there aren't any Fe2+ ions left to reduce the Mn7+ ions to Mn2+ so the solution turns pink since Mn7+ ions are purple?
    That's right but it's not what you wrote initially.
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    I'm doing edexcel A2 Chemistry, Part of our specification says :" Demonstrate understanding of the term ' dynamic equillibrium' as applied to states of matter, solutions and chemical reactions".

    I am perfectly okay with the understanding of it in terms of chemical reactions but know nothing of its application to "States of matter and solutions". (((((
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    What volume of oxygen, in cm3, would be required for 0.1 moles of cyclohexane to undergo complete combustion?

    C6H12 + 9O2 --------> 6H20 + 6CO2
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    (Original post by Jassy16)
    What volume of oxygen, in cm3, would be required for 0.1 moles of cyclohexane to undergo complete combustion?

    C6H12 + 9O2 --------> 6H20 + 6CO2
    What have you done to approach this question? I did this in my head (no writing down anything) and although I do not expect you to be able to do that, I would have thought that at this point in A level you would be able to do this question.
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    (Original post by TeachChemistry)
    What have you done to approach this question? I did this in my head (no writing down anything) and although I do not expect you to be able to do that, I would have thought that at this point in A level you would be able to do this question.
    28.8?
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    (Original post by Jassy16)
    28.8?
    No.

    How many moles of O2 do you need for 0.1 mol of cyclohexane?
 
 
 
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