Question

To explain how the result of a titration is affected if you titrate past the end point, calculate the percentage error for one drop past the end point of a 30 ml titration, using a 0.100m naoh titrant.

Answer 1

Titrating past the end point introduces a small but significant error. By calculating the moles of excess NaOH in one drop and dividing by the moles of NaOH at the equivalence point, we find a percentage error of approximately 0.167%, indicating a higher concentration of OH- in the solution.

Step-by-step explanation:

If we titrate past the end point of a 30 mL titration using 0.100M NaOH, we add more hydroxide ions than necessary to neutralize the acid, resulting in a solution with excess OH- ions. To calculate the percentage error, we must first determine the volume that one drop represents, as this can vary, but it is often around 0.05 mL. Given this volume, the number of moles of NaOH in one drop is:

n(NaOH) = Molarity × Volume = 0.100 mol/L × 0.00005 L = 0.000005 mol
The percentage error is calculated as:

Percentage Error = (Moles of excess NaOH / Moles of NaOH at the equivalence point) × 100%
Assuming the titration was done at the equivalence point, the moles of NaOH used would be:
n(NaOH at equivalence) = 30 mL × 0.100 M = 3.0 mL × 0.10 mol/L = 0.003 mol
Now, we can calculate the percentage error:

Percentage Error = (0.000005 mol / 0.003 mol) × 100% ≈ 0.167%
Titrating past the endpoint unnecessarily increases the volume of titrant, resulting in a calculation of acid concentration that is lower than it should be.