# Naoh standardization and titration of an

When one drop more NaOH is added than is required to react with the KHP in a sample, the sample becomes basic and the indicator changes color.

However, this, being only 0. In this experiment, you did things differently. We take the point where the indicator color first appears as an indication that we have added NaOH in an equivalent amount to the KHP present in the sample.

### Importance of standardizing a solution before titration

Using that solution, the average concentration of potassium hydrogen phthalate was found to be This means that due to systematic error, my accuracy has fallen by 9. Add 3 to 4 drops of phenolphthalein indicator to the KHP solution in the Erlenmeyer flask. In this experiment, you did things differently. The mols of sodium hydroxide were divided by the volume of 0. Rinse the buret with three portions about 5 mL of the NaOH solution. The theoretical value of the Sodium Hydroxide that was expected to be used was 9. In the past, if you had wanted to weigh out a sample, you first weighed an empty container, and then reweighed the container after the sample had been added to it. This might have caused some deviations because the volume of sodium hydroxide added was excess.

Calculate an average acid molarity using the two closest values. Another error was caused by the deviation in the mass of KHP. The volume of the 50 mL buret used in titration was recorded to the 0. The titrations had to be done with much care and precision because of its sensitivity. The percentage uncertainty calculated of the concentration of NaOH was 2. The average molarity of sodium hydroxide calculated from step before was multiplied by the volume of the titrating solution added and converted into mols of potassium hydrogen phthalate in the sample. The difference in mass before and after you removed the first sample is, of course, the mass of the first sample itself.

If the calculated acid concentrations from the first and second titrations vary by more than 0. Add 3 to 4 drops of phenolphthalein indicator to the KHP solution in the Erlenmeyer flask.

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