Suppose you titrated your standard acid (KHP) with the base to be standardized,

Question

Suppose you titrated your standard acid (KHP) with the base to be standardized, but addedseveral drops extra of the base (i.e. stopped the titration after the phenolphthalein indicator inthe solution turned very pink).

a. How would this affect your final determination of the molarity of the base? Wouldyou calculate the concentration to be greater or less than it really is?

b. If this calculated value was used to determine the molar mass of the unknown acid,what type of error would you have for the molar mass of the unknown acid? (i.e.would you overestimate or underestimate the molar mass value?) Support youranswer by, for every step in the calculation, determining whether the calculated valuewould be greater or less than it should be.

Explanation / Answer

a)

If you add extra volume of base, then volume of base will be MORE than the real Value, so the clacualtions of moles of base will be larger, i..e. the concentratio will be incorrectly higher (for the acid)

b)

This will overestimate the concentration of the new acid

since it will have a "larger" concentration, which requires more volme.

since

mmol of acid = mmol of base

Macid * Vacid = Mbase * Vbase

since Mbase is larger, Vbase required is more so more acid concentration is accounted

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