Question

The ?a of a weak monoprotic acid is 2.66×10−5. What is the pH of a 0.0757 M  solution of this acid?

Calculate the pH of a 0.6550  M NH3NH3 solution. NH3NH3 has a ?b=1.8×10−5

Answer 1

por + pH Son ve Know. РЧ Кој осн* 1 at 2 25° (н* 1 (он 1 10-15 Кыз н*] (оң) in general. T PT - log s (1) роч - log 10 [он add equation 0 and 6 we get РОН - | tog Сн*) + logio Сон) - logio (н*] [он ) as logab = loga + long le + pH РОН + pH | 4- о(нті (оң) 10 - 14-

PH for weak Monoprotic acid let say the acid is HA دم H+ + A C t: 2 teq 2 Non, ka 11 [+] (A) CHA so, Ka a (x) (x) So ka २२ en ) C-a

NOW, 94 >> x. me neglect x worit c ka c x² so kal NOW ow, x= [ht] ſkac Know PH -log Cit] PH ! -log lukach

pH of Lelak „Тоа 80 B 1 но BH't * он t: 0 с. б. t = teq х here kb [вн*][он 1 () L B1 1 K 12 (4) (4) 9) е >> 2. then he neglect a з .л. tc 2. — Кь а ? C 15) Кьс

Coh 1: X= Jкус Know рон - - logio [он | se, роҢ 17 - logio luksa) we know pH + pОН 14 Se, PH 14 + logio lukge)

2.66 x 10 - 5 PH of Q+) The Ka of weak monoprotic acid is what is the a 0.0757 solution of this acid given deta's are soln concentration of helak acid ? 0.0757 M ka 2.66 x 10-5 let take the weak acid as HA HA — Нt + A t=0 0.0757 X t= teq 0.0757- as, ㅈ a tHt] [A [HA] go ka x2 1 (0.07 0.0757-2)

put the value of of ka 5 2.66810 - X2 0.0757-6) 501 0.07.57 - X 3 7 5 93.9a² so 37.593.9 x ² - ta -0.0757 20 to x = 50:00143, 0.00140 AS concentrations can't can't lee negative a 000140 M si SI [H]- x 0.00 140 as he Know PH -tog 10 Cut so PH = -log 1o 10.00.140)

so PH 2.85 calculate the pH of 0.6550 M of NH3 Solution Rb of NH₃ = 1.8x10-5 I correct question) solm given deta's are concentration 0.6s5OM of NH3 Kb of NH₃ 1.8 X 10 Now, NH3 + H₂O THA + OH tio 0.655 20 t= teg 0.65S - x x as, K [NH ] (ou b INHO

80 Kb = 2.2 (0.655-x) put the the value of Ky in this equation 1.8 x 10 x 10-5 x2 (0.65 5-2) 0.655-X 55.555.5 x ² SI 55555.5 x 2 + x -0.655

Зо, 二 – 0:00 34+, о: Об3 4 9 as concentrations can't be negative s, 22 б. бб 34 2 а», у - сон 1 ко- оо 34 2 Н @s, K40 Kmoto Рон tot - logio &0, рон -log to to.oo 342) рон : 2 - 4 6 : hee Know pH teo H = 14- І. 59) 14 - 2.46 . Sо, ен 1 S4