2. When preparing a NaOH solution, a student did not allow the NaOH pellets to completely dissolve before standardizing the solution with KHP. However, by the time the student refilled the buret with NaOH to titrate the acetic acid, the remaining NaOH pellets had completely dissolved. Will the molarity of acetic acid in the vinegar solution, determined by the student, be too high or too low? Justify your answer with an explanation.
To determine whether the molarity of acetic acid in the vinegar solution will be too high or too low when using a NaOH solution where the pellets did not completely dissolve, we need to consider the reaction that occurs during the titration.
The reaction between acetic acid (CH3COOH) and sodium hydroxide (NaOH) can be represented by the following balanced equation:
CH3COOH + NaOH → CH3COONa + H2O
In this equation, one mole of acetic acid reacts with one mole of sodium hydroxide to produce one mole of sodium acetate and one mole of water.
During the titration process, the student measures the volume (in mL) of NaOH solution required to completely react with a known mass of acetic acid. This volume is used to calculate the molarity of acetic acid in the vinegar solution.
Now, let's consider the scenario where the NaOH pellets did not completely dissolve initially but dissolved completely by the time the student refilled the buret with NaOH solution.
If the NaOH pellets did not completely dissolve, it means that the concentration of NaOH in the solution is lower than the intended concentration. As a result, when the student titrates the acetic acid, they will end up using a lower concentration of NaOH than required.
Since there will be a shortfall in the amount of NaOH used during the titration, the calculated molarity of acetic acid will be higher than the actual molarity. This is because the student would have used less NaOH than required to fully neutralize the acetic acid.
Therefore, the molarity of acetic acid determined by the student will be too high when the NaOH pellets did not completely dissolve before starting the titration.
To avoid this issue, it is essential to ensure that all the NaOH pellets completely dissolve before standardizing the solution with KHP and proceeding with the titration. This ensures that the molarity of the NaOH solution used for titration is accurate and leads to a more precise determination of the molarity of acetic acid.