**How many moles of KOH(s) must be added to 200 mL of a 0.100 M solution of HNO**_{3}to bring the pH to 2.00?

Zaki-
Since a strong base is reacting with a strong acid, this is a stoichiometry problem, and not an equilibrium
problem. Follow these steps to solve it:
**Pick out the target**. You want moles of KOH.**List the given information**. You have 200 mL of a 0.100 M nitric acid solution. The final solution will have a pH of 2.00, which is the same as a hydrogen ion concentration of 0.010 M.**Connect the given information with the target**. It's best to work backwards from the target. If you had mol HNO_{3}that reacted, you could calculate mol KOH required. Whenever the problem involves a connection between two different substances,*you must have a mole-to-mole relationship between the two to solve the problem*. Write and balance an equation for the reaction between KOH and nitric acid to get this relationship.200 mL of 0.100 M HNO _{3}initially

0.010 M H^{+}finallymol HNO _{3}reactedmole-to-mole ratio

from balanced equationmol KOH Now you have to get moles of HNO

_{3}reacted. Moles reacted will be final moles minus initial moles. You know initial moles of HNO_{3}, since you know the volume and concentration of the initial HNO_{3}solution. You can estimate final moles too- you have to have a pH of 2.00, which is a hydrogen ion concentration of 0.010 M, and also a nitric acid concentration of 0.010 M. If you assume that the added KOH doesn't increase the volume significantly, the final volume of the solution is about 200 mL.**Do the math.**Set up a series of conversion factors so that units cancel to ultimately give you mol KOH.**Check the answer.**mol KOH should be less than moles of HNO_{3}present initially, since all of the acid wasn't neutralized.

General Chemistry Online! How can I adjust the pH of an HNO_3_ solution by adding KOH?

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Last Revised 08/17/15.URL: http://antoine.frostburg.edu/chem/senese/101/acidbase/faq/print-adjust-pH-HNO3-with-KOH.shtml