Question

1. a. For each set of solutions predict which one should have the lower pH.

i. 0.1 M Fe(ClO₄)₂ (aq) or 0.1 M Fe(ClO₄)₃ (aq)

ii. 0.1 M Ca(NO₃)₂ (aq) or 0.1 M Mg(NO₃)₂

b. Which is more Basic Towards B(CH₃)₃   - i. (CH₃)₂NH or ii. (CH₃)₃N. why?

Answer 1

1. a. Solutions prediction of pH

i. Fe(ClO4)3 has 3 ClO4- which is a weaker conjugate base of strong acid HClO4. It would hydrolyse and give OH- in solution. On the other hand, Fe(ClO4)2 has 2 ClO4- which gives OH- in solution. Wih higher ClO4- ions to hydrolyze in case of Fe(ClO4)3, the solution would be more basic.

Thus, Fe(ClO4)3 solution would have higher pH (more basic).

ii. 0.1 M Mg(NO3)2 would have higher pH as conjugate base is more free from conjugate acid in solution. Less ion-pair.

iii. Basicity coems from the ability of bases to donate a pair of electron to an acid. alkyl groups are electron donating in nature. B(CH3)3 is a lewis acid.

So, (CH3)3N is a sronger base than (CH3)2NH.