posted by Lamis on .
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 ?
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.