Chemistry and Chemical Reactivity (9th Edition)

a) $K_b=K_w/K_a=4.35\cdot10^{-4}$ b) It would be between hydrogen carbonate and hexaaquanickel ion. Water is an acid weaker than the ion and hydroxide is a base stronger than the molecule. c) $K_a=x\cdot x/(0.015-x)$ $x=[H_3O^+]=5.87\cdot10^{-7}$ $pH=6.23$