Question

How to standarize a tritant solution ?

Answer 1

Purpose: In this investigation you will determine how close a titrant concentration is to the calculated value based on the mass of titrant used. This will be accomplished by using the titrant to titrate a primary standard solution that you also will make from pure solid.

Materials and Methods:
Buret	Retort stand	Buret clamp	Pipette
Erlenmeyer flask	3 beakers	Pipette suction apparatus	Volumetric flask
Primary standard	Sodium hydroxide	pH paper

1. Clean and rinse all of the glassware. Dry the beakers
2. Using the fields on the data tables, calculate the mass of primary standard and sodium hydroxide needed to make the target concentrations.
3. Measure out an appropriate mass of primary standard and Sodium hydroxide into each dry beaker. The actual mass obtained need not exactly match the target masses. Do not waste time trying to get an exact amount of solid titrant or primary standard.
4. a) Use the volumetric flask to make your primary standard.
   1. Once the volumetric flask has been filled to the mark, pour the solution back into the beaker.
   2. Rinse the volumetric flask.
   3. Repeat the process to make your titrant solution.
5. a) Rinse the burette with a small amount of NaOH_(aq) titrant solution.
   1. Close the valve and carefully fill the burette.
   2. Eliminate the air space below the spigot by releasing some of the solution into a waste beaker.
6. a) Rinse the pipette by drawing up 10 mL of primary standard solution; dispose into waste beaker.
   1. Use the pipette to transfer 10.0 mL of primary standard to the flask.
7. Add 2 to 3 drops of phenolphthalein to the primary standard.
8. Titrate the primary standard to determine the concentration of the NaOH titrating solution. Repeat until you have three consistent trials. Rinse the flask after each trial.
   1. Record the initial volume indicated on the buret (V_i).
   2. Continuously swirl the acid mixture as base is added.
   3. As the endpoint is approached, you will notice that the pink colour of the indicator will persist for longer periods of time. At this point, base should be added drop-wise until the endpoint is reached. This will be indicated by a persistent light pink colour to the solution.
   4. Record the final volume indicated on the buret (V_f).
9. Rinse the pipette and buret with water and place inverted (spigot open) into the proper container.
10. Use the pH paper to estimate the pH of the remaining untitrated primary standard.
11. Dispose of all solutions as instructed.
12. Rinse and remaining glassware and return to its proper location.