Question

Standardization of a 0.05 M Solution of Sodium Hydroxide (Titrant Solution)

1. Place about 3 g of pure potassium hydrogen phthalate (KHP) in a clean dry weighing bottle and

dry the sample in the oven at 110°C for at least 1.5 h.

2. Remove the sample from the oven and cool in a desiccator for 20 min.

3. Weigh ca. 0.4 g of KHP into each of three clean, numbered Erlenmeyer flasks. Remember: The

weight of each sample should be determined by difference from the weights of the weighing bottle

before and after transfer of sample.

4. Add approximately 50 mL of distilled water to each flask.

CHEM 300: Analytical Chemistry E8-4

5. Swirl each flask to dissolve the KHP. Remember, this can take a while.

6. Add 2-3 drops of phenolphthalein indicator solution to each flask.

7. Pre-lab calculation: Calculate the amount of titrant that should be required for this titration,

using reasonable assumptions about the masses and volumes used in the above procedure.

How to calculate tritrant amount for the titration based on above information?

Answer 1

The balanced equation of reaction between sodium hydroxide and KHP (KHC₈H₄O₄) can be written as follows:

Thus, one mole of NaOH reacts with one mole of KHP. Molar mass of NaOH is 40.00 g/mol and that of KHP is 204.22 g/mol.

The number of moles of KHP in 0.4g can be calculated as follows:

Number of moles of KHP = (0.4 g) / (204.22g/mol)

Number of moles of KHP = 0.001959 mol

Thus, 0.001959 moles of KHP will require 0.001959 moles of NaOH.

Volume of 0.05M NaOH required = number of moles / molarity

Volume of 0.05M NaOH required = 0.001959 mol / 0.05M

Volume of 0.05M NaOH required = 0.03918L

Volume of 0.05M NaOH required = 39.18 mL

Thus, based on given information around 39.18 mL of titrant will be required for titration.