Question

Two 24.0mL samples, one 0.200 MKOH and the other 0.200 M CH3NH2, were titrated with 0.100 MHI. Answer each of the following questions regarding these two titrations.

What is the volume of added acid at the equivalence point for KOH?

What is the volume of added acid at the equivalence point for CH3NH2?

Predict whether the pH at the equivalence point for each titration will be acidic, basic, or neutral.

Predict which titration curve will have the lowest initial pH.

Thanks!

Answer 1

Sample 1 has 24 mL of 0.2 M KOH

                i) volume of acid required for KOH   is calculated by V1M1 = V2M2 since both n1 and n2 are =1

                volume of acid = (0.2 x 24 )/ 0.1 = 48mL

                ii) volume of acid required for CH3NH2

                volume of acid = (0.2x24)/ 0.1 = 48 mL since the base is monoacidic and acid is monobasic

                iii) At the equivalence point with KOH, the solution will be nneutral, since the salt formed is from a strong acid and strong base.

                iv) At equivalence point with methyl amine, the solution will be acidic, as the salt is formed from a weak base abd astrong acid HI.

                v) Since the titrations are starting from the base side, the strong base will have higher pH at the starting point and weak base has lower pH at starting point. Thus methylamine has lowest initial pH for the titration curve.