be slightly diluted and thus increasing molarity. Another error may be that the indicator does not change at the exact equivalence point, which will result in a higher number of moles of the solution in the buret than in the flask, leading to an increase in molarity. Additionally, the drops of indicator could get stuck to the sides of the flask, thus decreasing the numbers of mole that reach the solution, causing an increase in molarity. Steps that could be taken to prevent these errors from occurring would include properly rinsing the buret with transferred solution by tilting the buret to drain it down the sides to rinse the edges of the buret completely. To make sure the indicator does change at the exact equivalence point and the drops do not get stuck at the sides of the flask, the solution should be swirled as the base is added rapidly. When nearing the endpoint, the sides of the flash should be rinsed with a little distilled water and the NaOH should be slowly added, drop by drop, until the first drop of base leaves a faint pink color. Sources
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- Spring '11
- pH, Sodium hydroxide, H2SO4 solutions