Question

For the titration of 100.0 mL of 0.10 M formic acid (Ka = 1.77 x 10-4) vs 0.10 M aqueous LiOH, the

(a) pH at the equivalence point will be larger than 7

(b) pH at the equivalence point will be smaller than 7

(c) pH at the equivalence point will be exactly 7

(d) titration will require more moles of the base than acid to reach the equivalence point

(e) None of the statements above hold true.

Answer 1

As formic acid is weak acid and LiOH is strong base.the reaction is as follows

HCOOH + LiOH -----> HCOOLi +H2O

The salt HCOOLi produced in the reaction is basic and conjugate base from salt HCOO- reacts with water.The reaction is as follows.

HCOO^- + Li⁺ + H⁺ + OH^- ---> HCOO^- +Li⁺ +H2O

Here the solution produced is weakly alkaline.So pH at equivalence point will be greater than 7. So option a is true.

Here the molar ratio is 1:1. This means that moles of HCOOH is equal to moles of LiOH for equivalence.so option d is also incorrect.

only option a is true.