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    (Original post by chemphys)
    hi guys I've had this nagging problem in chem for a while
    say in the empa it asks you to work out a given value
    say it comes to 109.89088987
    `i round that to 3sf to get 110

    Then in part(ii) it asks me hence to work out say percentage error for 100 the true value
    Do i sub in my rounded answer of 110 or my accurate answer of 109.89088987 to get my answer for this part (ii) answer
    thanks this has been annoying me for ages becos using my rounded answer could introduce rounding errors
    Keep your value in calculator and use it calculate the percentage error, then round the final to 3 sf (or whatever asked)

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    (Original post by C0balt)
    Keep your value in calculator and use it calculate the percentage error, then round the final to 3 sf (or whatever asked)

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    ok thanks , but when showing your working do you write down the said value on the calculator becos technically the mark scheme says must use answer from part (i) and strictly speaking your 3sf answer was your final answer.

    Will the examiner realise that when you write the exact answer in working it is the same as your answer for the previous part just not rounded?

    Also do you do aqa thanks
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    (Original post by chemphys)
    ok thanks , but when showing your working do you write down the said value on the calculator becos technically the mark scheme says must use answer from part (i) and strictly speaking your 3sf answer was your final answer.

    Will the examiner realise that when you write the exact answer in working it is the same as your answer for the previous part just not rounded?

    Also do you do aqa thanks
    I do Edexcel
    In my physics practical I wrote a sidenote that unrounded value was used just to make sure (it takes less than 5sec and not much space so why not)
    I'm not sure the official view on this but my chem teachers tell me to write your rounded value on paper but use the calculator value
    Need confirmation though, not 100% sure

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    Anyone doing the empa?
    How are you preparing for task 3? I find it so hard!
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    Does this calculation look right?
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    (Original post by Kadak)
    Does this calculation look right?
    Which?

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    The one in the picture.I'm.meant to show the standard enthalpy of change.
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    (Original post by Kadak)
    The one in the picture.I'm.meant to show the standard enthalpy of change.
    What picture?

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    (Original post by Kadak)
    The one in the picture.I'm.meant to show the standard enthalpy of change.
    There's no picture

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    (Original post by samb1234)
    What picture?

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    Oh sorry this one.
    Attached Images
     
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    (Original post by Kadak)
    Oh sorry this one.
    Close but a slight mistake I think

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    (Original post by Kadak)
    Oh sorry this one.
    Sign

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    Yep

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    For reaction it's products - reactants

    Combustion it is CRaP
    Reactants - Products

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    (Original post by C0balt)
    For reaction it's products - reactants

    Combustion it is CRaP
    Reactants - Products

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    Oh Ty! I find it odd a formation reaction is exothermic.
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    (Original post by Kadak)
    Oh Ty! I find it odd a formation reaction is exothermic.
    Bond forming is always exothermic.
    Bond breaking is endothermic.
    That's a general rule you have to know.

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    (Original post by TheGreatImposter)
    Of course. I got a U in my first chemistry test and now I'm averaging As. Just gotta understand the content, go over it regularly and do past papers. I usually watch YouTube videos on the topics I find difficult and that helps.

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    Thank your your advise will definitely do that
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    (Original post by Disney0702)
    Hi there!

    I am an A2 Chemistry student.

    I got an A last year at AS level.

    In the March MOCKs I got a U grade for Chemistry but that was because I lacked understanding at that time.

    To help me understand better I bought the CGP text book which helped contribute to my A grade.

    I recommend you get it if you really want that high A grade.

    CGP AS Chemistry

    SAMPLE PAGES

    I also recommend you do lots of past papers so help strengthen your exam technique.
    Thank you so much
    I have that book
    And I will start to use it more wisely
    I really appreciate your reply
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    Can somebody help me please?
    When testing for a sulfate ion, you add BaCl2 to form a white precipitate. If no sulfate ion is present, what is the observation? Does the solution stay clear or can a different coloured precipitate form?
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    (Original post by prophetkid)
    Can somebody help me please?
    When testing for a sulfate ion, you add BaCl2 to form a white precipitate. If no sulfate ion is present, what is the observation? Does the solution stay clear or can a different coloured precipitate form?
    the solution stays colourless.
    All group 2 compound form white precipitate
    Only transition metals form coloured ones (dichromate, permagnate have colours but they are transition metal anion)
 
 
 
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