Question

which solution has the lower pH?

a)0.1 M HCL or 0.1 M HC2H3O2?

b)0.1 M NaOH or 0.1 M NH3?

c)0.1 M Na2CO3 or 0.1 M NaCl?

Answer 1

Remember lower pH means more acidic. Go through a reasoning process such as below. It works every time.
a. HCl is a stronger acid than HAc so HCl should be lower for the same concn (as it is here).
b. NaOH is a stronger base than NH3 so OH will be higher than NH3 for the same concn (as it is here). A higher OH means lower H^+ and higher pH.
c.Na2CO3 is hydrolyzed, NaCl is not. So the pH for NaCl is 7.0, that for Na2CO3 gives
CO3^2- + HOH ==> HCO3^- + OH^-
So this reaction is producing OH^- and HCO3^- (OH is strong base and HCO3^- a weak acid) so the solution will be basic which means higher pH.

Answer 2

citric acid solution