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Qs on KBB P942 #5. Plz.

Discussion in 'DAT Discussions' started by ddsjc2014, Jun 13, 2008.

  1. ddsjc2014

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    on P942 #5 why the mole of NaCl is 0.5 Mole.
    I don't get it. someone please explain this with little detail.
    Thanks guys.

    Question. If 10mL of 1M NaOH is titrated with 1 M HCl to a pH of 2, what volume of HCl was added?
     
    #1 ddsjc2014, Jun 13, 2008
    Last edited: Jun 13, 2008
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  3. Danny289

    Danny289 Member

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    for your second question answer is 10.20 mL?
     
  4. TeamGuo

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    this question indicates that you are titrating a strong base with strong acid which means when you react 2 things that are both strong they react in 1:1 fashion.

    So if you have 10 mL of NaOH, you can throw in 10 mL of HCl to get to neutral pH. The acid and base will cancel each other since they are both strong.

    So here once you throw in 10 mL of HCl to neutralize the sol'n you have 20 mL total volume at pH = 7. Now you want to know how much more of HCl do I need to add to get to pH = 2.

    1M HCl x X mL = 0.01 M x (20 + X) mL

    X = additional HCl being added.
    0.01 M = from the pH value of 2.

    So X = 0.2 mL, now you just add to the 10 mL ending with 10.2 mL of HCl.
     

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