Video Transcript
A 30-milliliter solution of nitric
acid was titrated against a 0.1-molar solution of potassium hydroxide. The addition of 26.6 milliliters of
potassium hydroxide was found to neutralize the nitric acid. What is the concentration of the
nitric acid? Give your answer to two decimal
places.
As nitric acid was titrated against
potassium hydroxide, a base, an acid–base titration occurred. Let’s start by writing a balanced
reaction equation for the reaction between nitric acid and potassium hydroxide. Nitric acid, HNO3, is reacted with
potassium hydroxide, KOH, to form potassium nitrate salt, KNO3, and water. The equation is already
balanced. The question asks to determine the
concentration of nitric acid. There are multiple methods to do
this, but we’ll use the following equation. 𝑐 represents concentration, 𝑣
represents volume, and 𝑛 represents number of moles. Note that when calculating
concentration with this equation, the volume can be in any unit so long as the units
match.
We are trying to work out the
concentration of acid. And we have been given its volume,
30 milliliters. For the number of moles of acid, we
can use the stoichiometric coefficient from the balanced equation, which is one. We can then do the same for the
other side of the equation and fill in the concentration, volume, and stoichiometric
coefficient of the base, potassium hydroxide. Anything divided by one is
itself. Therefore, we can remove the
denominators. We can then make the concentration
of nitric acid the subject by dividing both sides by 30 milliliters.
If we perform the calculation, the
milliliter units cancel, and we are left with a concentration of 0.0886 recurring
molar. The question asks for the answer to
be given to two decimal places. Therefore, the concentration of
nitric acid is 0.09 molar.
