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Question Video: Calculating the Concentration of Nitric Acid via Titrating against a Known Volume of Potassium Hydroxide Chemistry

A 30 mL solution of nitric acid was titrated against a 0.1 M solution of potassium hydroxide. The addition of 26.6 mL of potassium hydroxide was found to neutralize the nitric acid. What is the concentration of the nitric acid? Give your answer to 2 decimal places.

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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.

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