[Edher]

Saludos,

     What volume of 0.146 M KOH is needed for the complete neutralization of 20.00 mL of 0.0942 M H2SO4?

This is how I solved it,

20 mL x 0.0942 M H2SO4 = 1.884 mmol H2SO4

XmL x 0.146 mmol = 1.884 mmol KOH
                 1 mL

I got X = 12.9 mL. However, the book says it should be double that 25.8 mL. Why is that?

Thank You,
Edher

[Froggirl]

You are forgetting that H2SO4 is a diprotic acid (ie gives up 2 moles of H+ for every mole of H2SO4)!!
Your calculations took into account only half of the protons given up by H2SO4, therefore the answer was double what you calculated.  

[Edher]

Froggirl,

        I had a feeling that it had something to do with diprotic acids but since I missed that lecture I wasn't quite certain on how to apply its properties. Thank you.

Edher

[Donaldson Tan]

a monoprotic acid gives out 1 proton per molecule
a diprotic acid gives 2 protons per molecule

hence, the same concentration if a strong diprotic acid gives u twice as much H+ of a strong monoprotic acid.