Someone plz explain acid/base question

Discus: SAT/ACT Tests and Test Preparation: June 2004 Archive: Someone plz explain acid/base question
 By Leejwwc (Leejwwc) on Saturday, June 05, 2004 - 12:29 am: Edit

How many millimeters of a .200 molar sodium hydroxide solution must be added to a 100-millimeter solution of .100 molar nitric acid to obtain a pH of 7.

I don't see how they arrived at this answer. If you can, please show me the steps---I greatly appreciate any help you can give me

 By Wrathofgod64 (Wrathofgod64) on Saturday, June 05, 2004 - 12:52 am: Edit

Ok, so a pH of 7 means that equivalence point has been reached in a strong acid strong base titration, and the moles of acid (HNO3) equals the moles of base (NaOH). The moles of acid is .100 mL * .100 M = .01 mol HNO3. Therefore, we set this equal to the molarity of NaOH * the unknown volume as so
.01 = .200 M * V
.01/.200 = V
V = .05 L or 50.0 mL

hope that helps

 By Leejwwc (Leejwwc) on Saturday, June 05, 2004 - 07:17 am: Edit

thank you wrathofgod64!

 By Amylase (Amylase) on Sunday, June 06, 2004 - 09:10 am: Edit

this is so darn simple, lol