Any help with these chem problems would be awesome

Question

Consider 100.0 mL solutions of ammonia (NH3) and sodium hydroxide (NaOH), each with a concentration of 0.100 M.

    (a)Qualitatively compare the pH values of these two solutions. Support your comparison with an explanation.

(b) Suggest one method, other than pH, that could be used to distinguish the ammonia solution from the sodium hydroxide solution. State the expected results of the method.

(c) If the sodium hydroxide is diluted by a factor of 100, what would happen to its measured pH value?

Answer 1

a) The pH of the NaOH solution will be more alkaline (basic) than the solution of NH3. This is because when NH3 goes into solution, it produces NH4OH which is a weak base. NaOH is a strong base and dissociates more so will produce more OH- ions and hence will be more basic.

b) You could add CuSO4 and get a precipitate of Cu(OH)2 in both solutions. Then add more NaOH or NH4OH and the one in which the precipitate dissolves will be the ammonia solution. If the precipitate remains, it was the sodium hydroxide solution.

c) Original pOH of 0.100 M NaOH = -log 0.100 = 1

Original pH of 0.100 M NaOH = 14 - 1 = 13

Diluting by a factor of 100 will change the pH by a factor of 2 since pH is a log scale. The pH would be 11.

This is seen also as follows: 100 fold dilution --> 0.001 M NaOH

pOH = -log 0.001 = 3

pH = 14 - 3 = 11