what is the pH of 0.316 M KC6H5O? what is the pH of 0.245 M CH3NH3I?

Answer 1

C6H5O^- + HOH ==> C6H5OH + OH^-
Set up an ICE chart and solve with the following:
Kb = (Kw/Ka) = (OH^-)(C6H5OH)/(C6H5O^-)
Then pH = -log(H^+).

The CH3NH3I is done the same way but the equilibrium is a little different; CH3NH3^+ is an acid while C6H5O^- is a base.
CH3NH3^+ + H2O ==> CH3NH2 + H3O^+
Now follow the above; however,
Ka for CH3NH3^+ = (Kw/Kb)= (CH3NH2)(H3O^+)/(CH3NH3^+)
Finally, convert to pH.