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URGENT help needed pleeease! any Maths /chemists/physists?? help with a caculation! watch

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    hiya can someone plz help! I have to work out the concentration of ethanoic acid from the pH of the solution, and the concentration of the acids in vinegar from the pH of the solution. I have a worked example:

    Ka = 1.74 x 10-5 pH = 2.55

    [CH3COOH(aq)] = [H+(aq)]2 / Ka


    [H+] = pH
    -log10[H+] = 2.55
    log10[H+] = 2.55
    [H+] = 2.82 x 10-3 mol dm-3
    Ka = 1.74 x 10-5 mol dm-3
    Therefore, [CH3COOH(aq)] = (2.82 x 10-3)2 / 1.74 x 10-5
    = 0.457 mol dm-3


    but how do I get from the log10[H+] = 2.55 to [H+] = 2.82 x10-3 ?

    PLLLLEEEAASSSE please please someone help! I've been wraking my brains for hours and it has to be in tomorrow and I stil have the rest of my analysis and evaluation to go (i've been working solidly on it for the past 3 wks!-my cwk that is!) please someone help!
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    (Original post by emzie)
    hiya can someone plz help! I have to work out the concentration of ethanoic acid from the pH of the solution, and the concentration of the acids in vinegar from the pH of the solution. I have a worked example:

    Ka = 1.74 x 10-5 pH = 2.55

    [CH3COOH(aq)] = [H+(aq)]2 / Ka


    [H+] = pH
    -log10[H+] = 2.55
    log10[H+] = 2.55
    [H+] = 2.82 x 10-3 mol dm-3
    Ka = 1.74 x 10-5 mol dm-3
    Therefore, [CH3COOH(aq)] = (2.82 x 10-3)2 / 1.74 x 10-5
    = 0.457 mol dm-3


    but how do I get from the log10[H+] = 2.55 to [H+] = 2.82 x10-3 ?

    PLLLLEEEAASSSE please please someone help! I've been wraking my brains for hours and it has to be in tomorrow and I stil have the rest of my analysis and evaluation to go (i've been working solidly on it for the past 3 wks!-my cwk that is!) please someone help!
    2.82*10^-3 = 10^-(2.55)
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    (Original post by elpaw)
    2.82*10^-3 = 10^-(2.55)

    thanks does ^ mean x10 to the power of? coz i did that in my calculator and it said 'syn error'??

    i typed in 10 EXP -(2.55) and it said syn error? As you can see im not mathmatically minded!
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    If you tap in 1 EXP -2.55 you will get what you want and ^ simply means to the power of, so x10^ means times ten to the power of.
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    (Original post by emzie)
    thanks does ^ mean x10 to the power of? coz i did that in my calculator and it said 'syn error'??

    i typed in 10 EXP -(2.55) and it said syn error? As you can see im not mathmatically minded!
    syn error means youre putting it in the wrong order/using the wrong buttons. did you use the take-away '-'? you have to use the minus '-'
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    (Original post by emzie)
    thanks does ^ mean x10 to the power of? coz i did that in my calculator and it said 'syn error'??

    i typed in 10 EXP -(2.55) and it said syn error? As you can see im not mathmatically minded!
    ^ means "to the power of"

    not "x10 to the power of"
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    ahhhhh thanks guys yeh piggsy i was doing x10 to the power of instead of to the power of! oooppsss! thnx loads!!! bloomin eck tho i'm gunna be up all nyt - literally! o well my dad gave me loads of red bull! lol
 
 
 
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