Does anybody know what the equivalence point and the end point of this titration

Question

Does anybody know what the equivalence point and the end point of this titration reaection?

From the burettes on the front lab bench, deliver 20 mL of the KBrO3 solution into a clean, 250 mL Erlenmeyer flasks. While it is not necessary for the volume to be exactly 20 mL, it is necessary for you to know the exact volume used by reading the initial and final burette readings to the nearest 0.02 mL and subtracting the initial reading from the final reading. To the flask, add exactly 10 mL of NH3OHCl using a volumetric pipette.

Working under a fume hood, using a graduated cylinder add 15 mL of 5M HCl to the flask, swirling the flask vigorously to mix the solutions thoroughly. Cover the flask with a watch glass and allow the solution to stand in the fume hood for approximately 10 minutes before removing it from the hood and performing the titration. During the reaction time, closely examine the contents of the flask for colour changes, evidence of gas evolution, temperature changes, etc. Record detailed observations on your data sheet.

Rinse the the burette with about 5 mL of the stock sodium thiosulphate solution and then 47 fill the burette with that solution. Record the initial burette volume. At the end of the 10 minute reaction period, add about 5 mL of 10% potassium iodide solution to the reaction flask. Mix the contents thoroughly by vigorously swirling the flask, and immediately titrate the solution in the flask with sodium thiosulphate. Once the solution colour has faded to yellow, add 2 mL of starch indicator. ( The indicator should have been measured out prior to beginning the titration in order not to delay completion of the titration.) N.B. The starch indicator must not be added prematurely. Wait until the solution is yellow, without any brown or reddish tinge before adding it. Note the change in the solution which occurs upon addition of the starch indicator and resume the titration with dropwise addition of titrant. The end point is reached when the solution colour changes from pale blue to colourless. If the starch indicator is added at the appropriate stage of the titration, the end point colour change is quite distinct and easy to see. It is observed most easily when the titration flask is resting on a white background.

Explanation / Answer

While carrying out titrations, one must always remember, that the equivalence point is achieved first, that is, when the solution is alost colourless except for a hint of pale blue still seen in the flask. On adding yet another drop of the titrant from the burette, all of the blue colour disappears. Thus we can say that the end point has been reached.

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