A student standardizes a solution of aqueous NaOH against a measured mass of solid potassium hydrogen phthalate. She then uses this NaOH solution to titrate a measured mass of an unknown monocarboxylic acid to its phenolphthalein endpoint to determine its molar mass.
1. Which errors will lead to a value of the molar mass that is too high?
I. The potassium hydrogen phthalate is partially hydrated.
II. The NaOH solution is allowed to stand after being standardized and absorbs some carbon dioxide from the air.
(A) I only
(B) II only
(C) Both I and II
(D) Neither I nor II