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Gen chem question

Discussion in 'DAT Discussions' started by 151AND8TH, Jun 5, 2008.

  1. 151AND8TH

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    How many ml of 3M H2SO4 are required to neutralize 30 ml of 4M NaOH?

    I thought the answer would be 40 ml. but its 20 ml. (due to the 1:2 ratio after the equation is balanced... i guess)... anyway, I still dont understand the concept on why the volume of H2SO4 had to be cut in half. Can someone please elaborate?
     
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  2. Doctor PJ

    Doctor PJ Member
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    2 hydrogen atoms there make the solution stronger. Remember to use Normality x Volume here. 3M x 2 Hydrogens =6N x V = 120. V = 20ml

    It takes a smaller volume or amount to dissolve something that has a lower moles/solution than the 6N.
     
  3. 151AND8TH

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    perfect! thank you! .. normaly, when do you look for NORMALITY? becuase for this problem I obviously used m1v1=m2v2
     
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  4. nt4reall

    nt4reall New Member
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    H2SO4 + 2 NaOH --> Na2SO4 + 2 H2O

    Find the mole number of NaOH = Molarity x Volume
    = 4 M x 0.3 L = 0.12 mol
    1 mol H2SO4 needs 2 mol NaOH ( the equation above )
    Therefore , 0.12 mol of NaOH will need 0.06 mol H2SO4
    The volume of H2SO4 = mole number/molarity
    = 0.06 mol/3 M
    = 0.02 L = 20 mL
     

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