Question

The use of good technique while doing this experiment is very important. Briefly explain how the following technique errors would affect the determination of the molar concentration of acetic acid in vinegar

1. A student stops the titration when the pink persists through the solution for less than 10 s.

Explain your reasoning.
A. When the titration is stopped before the real endpoint has been reached, the calculated volume of sodium hydroxide needed for the titration will be too low. This will cause the number of moles of base that is calculated to be low, and thus the moles of acid will be calculated as too low. The lower number of moles of acetic acid will cause the molar concentration of the vinegar to be too low. B. When the titration is stopped before the real endpoint has been reached, the calculated volume of sodium hydroxide needed for the titration will be too low. This will cause the number of moles of base that is calculated to be low, and thus the moles of acid will be calculated as too low. The lower number of moles of acetic acid will cause the molar concentration of the vinegar to be too high. C. When the titration is stopped before the real endpoint has been reached, the calculated volume of sodium hydroxide needed for the titration will be too high. This will cause the number of moles of base that is calculated to be low, and thus the moles of acid will be calculated as too low. The lower number of moles of acetic acid will cause the molar concentration of the vinegar to be too low. D. When the titration is stopped before the real endpoint has been reached, the calculated volume of sodium hydroxide needed for the titration will be too low. This will cause the number of moles of base that is calculated to be low, and thus the moles of acid will be calculated as too high. The lower number of moles of acetic acid will cause the molar concentration of the vinegar to be too low.

Answer 1

option A is right.

sodium hydroxide is mono hydroxide and acetic acid is mono protic acid. so during the titration...

moles of NaOH = moles of CH3COOH

and concentration of vinegar = moles of acetic acid / solution in Liter

therefore, if the titration is stop before the real endpoint reached, calculated volume of NaOH will be too low ( option C is incorrect) and moles of NaOH will be low ( moles = molarity * volume of solution). Therefore moles of acetic acid will also low ( option D is incorrect). If, moles of acetic acid low means molar concentration of vinegar to be low (option B is incorrect)