Question

LABORATORY 8 Post-Lab 1. Explain how each of the following errors would have altered your results. Clearly explain why your calculated answer would be high, low, or unchanged. (A single word answer is not acceptable.) a. You decided to take the pH after each addition of 5.0 mL of NaOH rather than after every 0.5 mL during the neutralization of your acid sample. b. While using the Half Volume method, your solution was dark pink (you overshot the endpoint) and you added the unreacted acid to this solution. c. You refilled your buret between titrations of your unknown acid. Instead of using 0.1 M NaOH as you did for the first titration, you used 0.2 M NaOH.

Answer 1

a) When we take pH reading after eveny sml rather than taking every 0.5mi, then there is a very high chance that we miss the neulralization point. Also, the charge in pH is very high which may result in high ervol in pka. b) When the unvedeled acid is added to the abicady overshol Solution, there is a high chance of erral as the current concentration is unknown. c) If the molarity of the base is changed in between the Hitration, there is a chance that there is a sudden change in the pH values which causes a high error in the value of Ka. H+ + A - HA o I 01224 + ta a a o E 0.1224-a Af - 3 equillibrium C-PH) SABH (-2.95) Q = [H+] = 10 VE 10 = 101210 m. Ka = [H+] [A-3/6443 á 6011334 -) = (,12 x1039_ 125x10 " _ 1.0341057 Prea = - 10g ka = -log (1.03410%) = 14.98] Oman 0.12-178 (0.1224 - 1. 12X1033,