chemistry question

[jstyt7]

How many milliliters of 3.0 M H2SO4 are required to neutralize 3.0 mL of 4.0 M NaOH?

answer: 0.5*((3*4)/1000)*(1000/3)= 20 ml

What volume of 18 M H2SO4 should be used to prepare 300 ml of 6 M H2SO4 solution?

M1V1=M2V2 --> V1= 100 ml


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Can some one please explain the difference between those two question and where did 0.5 come from in the first question.


Thanks.

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[Ferenzi]

H2so4 is diprotic whereas Naoh is monoprotic. So you would only need one half of what's calculated if only m1v1=m2v2 is used.