Data for Question B:
(initial)[CH3COOH] = 0.500 mol dm–3 and) eqm [CH3COOH] = 0.200 mol dm–3;
(initial)[CH3COO–] = 0.300 mol dm–3 and) eqm [CH3COO–] = 0.300 mol dm–3;
The Attempt at a Solution
Question A) " FInd the pH of a mixture of 50.0 cm3 of 0.100 mol dm–3 aqueous ammonia and 50.0 cm3 of 0.0500 mol dm–3 hydrochloric acid solution"
The teacher told us to do this by equating [NH3] to [NH4]. I just don't get the logic! Ammonia is a weak base, so it's initial concentration in undissociated form is unchanged and stoichiometrically its products are formed in 1:1 ratios, but I haven't ever seen THIS relationship anywhere, can someone please explain this to me?
Question B) " Determine the pH of a solution formed from adding 50.0 cm3 of 1.00 mol dm–3 ethanoic acid, CH3COOH(aq), to 50.0 cm3 of 0.600 mol dm–3 sodium hydroxide, NaOH(aq)." Refer data provided.
One would assume if a weak base behaved as seen above a weak acid would too but the answer booklet implies that ethanoic acid doesn't! Which is peculiar!
[CH3C00H] DOESN'T EQUAL [CH3COO-] apparently!? And how on earth will [CH3COO-] have a initial concentration at all?!
How does that make sense? I can understand the equilibrium concentration being hte difference between acid and base concentration, 0.3 mol dm3 makes sense, but the INITIAL concentration MUST be an error!?
Thank you a lot! :D