Which of the following is a serious source of experimental error? a. The sodium hydroxide is not mixed completely in the Florence flask.
b. The buret is not conditioned.
c. The KHP samples are dissolved in 50 mL (not 25 mL) of distilled water.
d. Two drops (not one drop) of phenolphthalein indicator is used.
e. Bubbles are not cleared from the tip of the buret.
f. The Erlenmeyer flasks are not dry before pipetting the vinegar samples.

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Answerthe half-reaction having the greatest tendency to occur at the anode:     i₂(aq) + 2e⁻  ⇄ 2i⁻  ;   e = +0.53 v======oxidation occurs at the anode. we must therefore find the half-reaction with the greatest tendency to oxidize.the given values of e are reduction potentials (the form of the half-reactions are of reduction).the lower the reduction potential, the higher the potential to oxidize. the half-cell with the lowest reduction potential will have the greatest tendency to oxidize at the anode.the half-reaction having the greatest tendency must be    i₂(aq) + 2e⁻  ⇄ 2i⁻    e = +0.53 vbecause its reduction potential is the lowest out of the three.

If your on odysseyware i believe the answer would be c. 

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