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Homework Help: Acids and bases

  1. Nov 26, 2013 #1
    1. The problem statement, all variables and given/known data

    2.75 g of mgo(s) is added to 70.0 ml of 2.4 mol/l hno3(Aq) is the concentration that results from the solution acidic or basic? What is the concentration of the ion that is responsible for the character of the solution. What is the pH ?
    2. Relevant equations



    3. The attempt at a solution
    First I found the mols of mgo and the mols of Hno3.
    ( convert g to mol for Mgo and multiplied the concentration by vol for HNo3)

    Since they are not in a 1:1 ratio as seen by the balanced chemical equation I took the one with the greater mol(0.06822) which would be HNo3 and multiplied it by 2(molar ratio)

    I then used this mol and divided it by the vol of the solution to get 1.95mol/l
    However the book is saying .46.. What did I do wrong?
    Last edited: Nov 26, 2013
  2. jcsd
  3. Nov 26, 2013 #2


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    Staff: Mentor

    Hard to say what you did, as your description is rather cryptic.

    Hint: this is a limiting reagent question. Whatever is left after the reaction will be responsible for the solution pH.

    Please pay attention to the way you type formulas. No such things as mgo or hno3.
  4. Nov 26, 2013 #3

    Usually you use the excess to find the concentration of the ion. What would the limiting reagent have to do with it?
  5. Nov 26, 2013 #4
    I know how you are supposed to do this problem however I am not getting the answer
  6. Nov 26, 2013 #5


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    Staff: Mentor

    Ignore the pH part now. Solve the stoichiometry. What is left after the reaction?
  7. Nov 26, 2013 #6
    Isn't that what I did above?
  8. Nov 26, 2013 #7
    I multiplied by 2 using stoichmetry
  9. Nov 26, 2013 #8
    I got it
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