CHM135H1 Lecture Notes - Lecture 22: Acid Strength, Equilibrium Constant, Weak Base

• School: UTSG
• Department: Chemistry
• Course: CHM135H1
• Professor: Gilbert Walker, Eugenia Kumacheva, Kristine Quinlan

Document Summary

Chm135: lecture 21 acid base equilibria (part 3/3) October 26, 2018 (relevant reading: chemistry 2nd ed. Summary of the last lecture product constant for water. =[(cid:2871)+][ ]=(cid:883). (cid:882) (cid:883)(cid:882) (cid:2869)(cid:2872) (cid:4666)(cid:884)(cid:887) (cid:1829)(cid:4667); applicable to water and aqueous solutions, ion . Strong acid completely dissociates in aq. Strong base completely dissociates in aq. We learned to make assumption: ignore [(cid:2871)+] from dissociation of water [ha]init ~ [ha] Weak acid (base) need to consider equilibrium to find eq. concentrations ph. What happens with ph when weak acid concentration decreases? (a) have a 0. 01m solution of acetic acid; the degree of dissociation is 1% [h3o+] ~ 10-4 m; ph ~ 4 (b) dilute solution ten fold to 0. 001m; the degree of dissociation is now 5% Example: using molecular scenes to determine the extent of ha dissociation. Plan: we are given the percent dissociation of the original ha solution (33%), and we know that the percent dissociation increases as the acid is diluted.