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    What did people get for the Mr of M in MHCO3?
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    (Original post by SPKY13)
    What did people get for the Mr of M in MHCO3?
    i got 149.1 but for the question before I used 3 of the titre values to find the moles.
    Apparently you were suppose to use only 2 values which were 0.1 cm^3 of each other
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    (Original post by GabbytheGreek_48)
    for ful redox equation you just combine the two half equations and eliminate the electrons so
    2Cl+2CLO-+4H ---> 2CL2 + 2H2O
    Thank you!

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    (Original post by dragonblazer11)
    does anyone have any good notes, links or know any videos to help me learn the practicals for paper 2?
    Try chem revise and check for the topic the practicals are in. They have some good notes.

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    (Original post by DaVinciGirl)
    Hey, I was wondering if you remember how many marks was that Barium sulphate question was? Thanks!

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    As it has already been pointed out, it was 4 marks. Sorry for late reply: been playing Overwatch!
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    How many marks was it for each of the half equations and the full redox equation! Was it 1 mark each?
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    (Original post by Hbassett26)
    How many marks was it for each of the half equations and the full redox equation! Was it 1 mark each?
    Yeah it was.
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    must be ClF3 as all the other have cancelling dipoles.
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    (Original post by JoscelinL)
    must be ClF3 as all the other have cancelling dipoles.
    The dipoles on that cancel aswell?
    There is no net positive or negative region on that molecule.
    Im not sure for that Q i put BF3
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    (Original post by abxo)
    The dipoles on that cancel aswell?
    There is no net positive or negative region on that molecule.
    Im not sure for that Q i put BF3
    BF3 has cancelling dipoles due to no lone pairs. Pretty sure it's ClF3
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    (Original post by mani119)
    i got 149.1 but for the question before I used 3 of the titre values to find the moles.
    Apparently you were suppose to use only 2 values which were 0.1 cm^3 of each other
    I got 149.1 also , not sure what you mean about the 3 values they were all different by the same amount so you couldn't rule one out ? Any how they can only penalise you for that mistake once so at worse thats a 1 mark loss
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    (Original post by britishtf2)
    Find mean and mol HCl in 25cm^3 [3]
    Find Mr of MHCO3 [3]
    How could you reduce percentage uncertainty? [2?]

    I think that was it - maybe another part. I am not sure.
    6 Maker was how to make a standard solution, which may have been part of it.
    Do you remember how you found the Mr of MHCO3? I remember getting an answer that didn't make sense ://

    Thanks.
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    (Original post by DaVinciGirl)
    Thank you!

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    yeah that should b it i think because you usually combine the half equations and cross out the electrons
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    (Original post by AceMaths)
    The gas left over was 30 , you didnt take into account what was in excess and in limited. Dont post answers if they're wrong.
    I believe the question was the volume of gas at the end of the experiment, not the volume of product. I don't think you could lose volume so wouldn't 50cm^3 be correct? my logic on this could be wrong though
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    For the overall equation can you divide it all by 2?
    Also predicted raw marks for full ums?
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    (Original post by Muddleing_thru)
    Do you remember how you found the Mr of MHCO3? I remember getting an answer that didn't make sense ://

    Thanks.
    I used the 3 titre values, although I am pretty sure you are only supposed to use the 2 within 0.1cm^3, to find mean HCl reacted in 25cm^3.

    Use this mean and the concentration of HCl to find how much HCl reacted. It is a 1:1 ratio, but we need how much in 250cm^3 so multiply by ten.

    That is how many moles of MHCO3 reacted. You have mass and moles, so Mr = Mass/Moles, to get an answer around 149 for using 3 titre values; not sure what you get if you used 2 titre values, but it won't differ too much.

    Marks are probably for:
    i)
    Correct method of finding mean,
    Correct mean,
    Correct moles. [3]

    ii)
    Correct MHCO3 moles in 250cm^3 {ECF, likely},
    Use of Mr = Mass/Moles,
    Correct Mr {ECF likely} [3]

    Hope this helped.
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    (Original post by SM-)
    For the overall equation can you divide it all by 2?
    Also predicted raw marks for full ums?
    Raw marks for UMS is likely to be standard percentages or less. I reckon 75~% for an A with 10% increments, but I could be wrong.
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    And for the overall equation of Cl and whatever it was you got everything multiple of 2 so can you divide it through by 2?
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    (Original post by britishtf2)
    I used the 3 titre values, although I am pretty sure you are only supposed to use the 2 within 0.1cm^3, to find mean HCl reacted in 25cm^3.

    Use this mean and the concentration of HCl to find how much HCl reacted. It is a 1:1 ratio, but we need how much in 250cm^3 so multiply by ten.

    That is how many moles of MHCO3 reacted. You have mass and moles, so Mr = Mass/Moles, to get an answer around 149 for using 3 titre values; not sure what you get if you used 2 titre values, but it won't differ too much.

    Marks are probably for:
    i)
    Correct method of finding mean,
    Correct mean,
    Correct moles. [3]

    ii)
    Correct MHCO3 moles in 250cm^3 {ECF, likely},
    Use of Mr = Mass/Moles,
    Correct Mr {ECF likely} [3]

    Hope this helped.
    Thanks a mil. I did something similar to this so must have made a mistake somewhere with converting between units... oh well. Thanks again!
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    (Original post by ChuckyTownXL)
    I got 149.1 also , not sure what you mean about the 3 values they were all different by the same amount so you couldn't rule one out ? Any how they can only penalise you for that mistake once so at worse thats a 1 mark loss
    thats wat i was thinking so hopefully stille d marked yself down for that though just incase
 
 
 
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