Chemistry Help

  1. HELP!!!!!

    I am having a complete brain meltdown and cannot figure out the following problem.

    How many milliliters of 0.250 M phosphoric acid are required to completely neutralize 15.62 mL of a 0.100 M KOH?

    Any help would be greatly appreciated.
    Daryn
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  2. 5 Comments

  3. by   springgarden
    I am taking chemistry now - this semester - but I have no clue how to solve you question!!
    I use Yahoo Questions/Answers for my chemistry assignments. There a lot of people willing to assist and answers any questions posted promptly.
    I'll recommend it for you to try.
  4. by   leximast1
    I am guessing because we are starting the acid & base chapter tomorrow but I think you can use the C1V1 = C2V2 equation.
    So (.250M)(15.62ml) = (.100M)(V2)
    V2 = 39ml
    Does that work? I could be way off. Lexie
  5. by   pekinsweety86
    edited...
    Last edit by pekinsweety86 on Nov 20, '06
  6. by   danh3190
    Quote from CTRNTOBE
    HELP!!!!!

    I am having a complete brain meltdown and cannot figure out the following problem.

    How many milliliters of 0.250 M phosphoric acid are required to completely neutralize 15.62 mL of a 0.100 M KOH?

    Any help would be greatly appreciated.
    Daryn
    Don't forget that each molecule of phosphoric acid aka H3(PO4) can give up 3 H+ ions to neutralize the KOH. In other words, 1/3 mole of phosphoric acid will neutralize 1 mole of KOH.

    So you can figure out the number of moles of KOH you have to neutralize. (remember that the "M" stands for moles/liter or moles/1000 mL)
    Then you can figure out how many ml's of .25M H3PO4 equals the number of moles of KOH.
    Then divide that number of ml's by 3 since you only need 1/3 as much.
  7. by   catzy5
    Quote from danh3190
    Don't forget that each molecule of phosphoric acid aka H3(PO4) can give up 3 H+ ions to neutralize the KOH. In other words, 1/3 mole of phosphoric acid will neutralize 1 mole of KOH.

    So you can figure out the number of moles of KOH you have to neutralize. (remember that the "M" stands for moles/liter or moles/1000 mL)
    Then you can figure out how many ml's of .25M H3PO4 equals the number of moles of KOH.
    Then divide that number of ml's by 3 since you only need 1/3 as much.


    thats beautiful thank you so much! I didn't even post the question but I have my last unit exam this morning and was sitting here studying I totally forgot about the H3 being worth only 1/3 as much and I solved everything else but got stuck at the end. thanks for taking the time to help.

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