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    I have searched the internet for about an 1 hour and looked through my book so many times but I have some questions I have no idea how to answer. Could anyone just help me out?
    How do I calculate the volume of a solution from using pH and 25.0cm3 sample of 0.0850 mol dm-3?
    how do I calculate the pKa only using the temperature and Ka?
    Any help would be nice, thanks x
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    (Original post by ashpittawayx)
    I have searched the internet for about an 1 hour and looked through my book so many times but I have some questions I have no idea how to answer. Could anyone just help me out?
    How do I calculate the volume of a solution from using pH and 25.0cm3 sample of 0.0850 mol dm-3?
    Your question makes no sense. You already have the volume of the solution!



    how do I calculate the pKa only using the temperature and Ka?
    Any help would be nice, thanks x
    you don't need the temperature:

    pKa = -log10Ka
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    (Original post by charco)
    Your question makes no sense. You already have the volume of the solution!


    this is my exact question: A 25.0cm3 sample of 0.0850 mol dm-3 hydrochloric acid was placed in a beaker. distilled water was added until the pH of the solution was 1.25. Calculate the volume of the solution formed. (3)




    you don't need the temperature:

    pKa = -log10Ka
    Thanks I realised after I posted it x
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    this is my exact question: A 25.0cm3 sample of 0.0850 mol dm-3 hydrochloric acid was placed in a beaker. distilled water was added until the pH of the solution was 1.25. Calculate the volume of the solution formed. (3)

    how do i calculate the volume?
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    (Original post by ashpittawayx)
    this is my exact question: A 25.0cm3 sample of 0.0850 mol dm-3 hydrochloric acid was placed in a beaker. distilled water was added until the pH of the solution was 1.25. Calculate the volume of the solution formed. (3)

    how do i calculate the volume?
    you're really pretty
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    (Original post by LisaNikita)
    you're really pretty

    Thank you, so are you x
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    (Original post by ashpittawayx)
    this is my exact question: A 25.0cm3 sample of 0.0850 mol dm-3 hydrochloric acid was placed in a beaker. distilled water was added until the pH of the solution was 1.25. Calculate the volume of the solution formed. (3)

    how do i calculate the volume?
    As you mentioned it earlier, do you have the Ka?
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    (Original post by h3rmit)
    As you mentioned it earlier, do you have the Ka?
    No, that was for a different question x
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    Okay. Firstly you know that there is initially 0.0850 moldm-3 of H+ ions. Using: (Volume x Concentration)/1000 you will get moles- Which in this case is 2.125 x 10-3 moles of H+ ions. This number of moles will stay the same after the distilled water is added. Using [H+] = 10-pH Find the concentration of H+ ions after the distilled water is added. Then rearrange the first equation: (moles x 1000)/Concentration and this will give you the final volume, using the concentration you just calculated and the moles you calculated before that. The volume will be in cm3.
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    (Original post by ashpittawayx)
    this is my exact question: A 25.0cm3 sample of 0.0850 mol dm-3 hydrochloric acid was placed in a beaker. distilled water was added until the pH of the solution was 1.25. Calculate the volume of the solution formed. (3)

    how do i calculate the volume?
    The concentration of the hydrogen ions is the same as the acid as it is a strong acid.

    Work out the concentration of hydrogen ions in the target solution.

    You know how many moles of acid you are starting with (and ending with) mol = MV

    So now calculate the overall volume of solution with this number of moles which will give you the target concentration.
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    Ok so what you need to do:

    Find moles of HCl initially in solution using cv/1000.

    You know that [H+] and therefore [HCl] in the final solution is equivalent to the value for 10^-1.25.

    Use the expression c=1000*moles/volume:

    10^-1.25 = 1000 x moles/ 25 + x

    Rearrange to find x.

    Total volume is 25 + x.

    If I'm wrong anybody please correct me
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    (Original post by hoafanuk)
    Ok so what you need to do:

    Find moles of HCl initially in solution using cv/1000.

    You know that [H+] and therefore [HCl] in the final solution is equivalent to the value for 10^-1.25.

    Use the expression c=1000*moles/volume:

    10^-1.25 = 1000 x moles/ 25 + x

    Rearrange to find x.

    Total volume is 25 + x.

    If I'm wrong anybody please correct me
    Thank you, turns out I had already done half but didnt know where to go after, nice to know i would probs get some marks in the exam if it came up
 
 
 
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