The weight of dry acid are measured to the nearest milligram; however the volume of water in which it is dissolved is never a critical concern--water is even added to the Erlenmeyer flask while washing its wall during the titration . Explain why the addition of water to the flask is not critical to the analysis whereas its addition to the NaOH solution is ?

Question

The weight of dry acid are measured to the nearest milligram; however the volume of water in which it is dissolved is never a critical concern--water is even added to the Erlenmeyer flask while washing its wall during the titration . Explain why the addition of water to the flask is not critical to the analysis whereas its addition to the NaOH solution is ?

Thank You.

Answer 1

Water added to the NaOH dilutes the base and changes the molarity.

There are two ways to look at the water added during titration to the Erlenmeyer glask.
1. Water added to the flask dilutes the sample BUT it dilutes the NaOH being added by the same amount.
2. What is the NaOH titrating? It is titrating the moles acid in the Erlenmeyer flask. Adding water to the flask does NOT change the number of moles acid initially present. Therefore, the NaOH titrates to the point where moles = moles and adding water to the flask has nothing to do with it.

Answer 2

The addition of water to the Erlenmeyer flask during the analysis is not critical because the volume of water does not affect the concentration or reaction of the dry acid being measured. In this case, the weight of the dry acid is the important parameter for the analysis, so it is measured to the nearest milligram. The volume of water in the flask is not crucial because it does not directly impact the measurement or the accuracy of the analysis.

On the other hand, the addition of water to the NaOH solution is critical because it directly affects its concentration. Adding water to the NaOH solution will dilute the concentration of NaOH, which can impact the reaction or the accuracy of the analysis. In titration, the concentration of the titrant (NaOH) is crucial for accurately determining the analyte's concentration. Therefore, any changes in the concentration of the NaOH solution, including adding water, would affect the final result. To ensure accurate measurements, the volume of the NaOH solution should be carefully controlled, and any additional water added must be taken into consideration and factored into the calculations.