Question

1. Consider a weak acid, HA, and the salt of its conjugate base, NaA. For HA, K = 1.2 x 100 Solution: 20.0 mL of 1.0 M NaA, 25.0 mL of 1.0 MHA and 5.0 mL of 1.0 M HCI. a) What are the major species originally in the solution before any acid-base reactions occur? b) Considering the major species in solution, write the reaction that occurs. c) Calculate the pH of this solution. d) Is this solution a buffer solution? Explain why or why not. 2. Consider a weak acid, HA, and the salt of its conjugate base, NaA. For HA, K = 6.5 x 10-6 Solution: 15.0 mL of 1.0 M NaA, 20.0 mL of 1.0 MHA and 5.0 mL of 1.0 M NaOH. a) What are the major species originally in this solution before any acid-base reactions occur? b) Considering the major species in solution, is there a reaction that occurs that goes essentially to completion? If so, write the reaction. c) After the reaction goes to completion, determine the concentrations of (HA) and [A] in solution and calculate the pH of this solution. d) Is this solution a buffer solution? Explain why or why not. 3. Consider a solution containing a weak acid, HA, and its conjugate base, A. For a solution containing 15.0 mL of 1.0 M HA and 20.0 mL of 1.0 M NaA, the measured pH = 9.21. Calculate the corresponding value of K for HA. A 0.1 M CH,COOH solution is titrated with 0.1 M NaOH. a) Write the net ionic equation for the reaction that occurs during the titration. b) At what point in the titration will the pH of the solution be equal to pK? Use equations to explain your answer. c) Draw the titration curve, pH (y-axis) versus Volume of NaOH (ml), and show at what point in the titration the pH of the solution is equal to pKg. Show how you determined the point where pH = pka. d) On your graph, draw a box around the buffer region.

can someone please help me out with questions 1-5, please

To add more information this was given to me for a lab that used a weak acid and we added a strong base through titration. We just observed how the ph changes. Later we then used a buffer with a weak acid to see how buffers affect ph change. These questions are basically surrounded around those topics to help us prepare. However, I'm kinda confused about answering them because weak acid and their conjugate bases confuse me. So please can you help me out?

Answer 1

In the fifth question, the meter is showing pH of 3.50 when distilled water was taken in the beaker because, may be the beaker was not washed properly some sort of acid either hcl or ch3cooh had been there in the beaker.

Distilled water has a oh of 0 as it does not contains negligible amount of H+ .

To obtain accurate readings of distilled water and that of solutions in part second and third the beaker has to be rinsed properly with that solution which has to taken in the beaker otherwise flawed observation occurs.

some, 1.04 NaA e asml INHA & 5ml of Innice 31 15 me HALIN) +one IH NAA species Na A ~ HA = Matt A- H++A- H++ ce- M="Let) n NaA = 20 XIX10-3- "HA 0.025 mol ntce- 0.005 holes PH 9.21 katha) = ? HA - 15 X -- 02 Hee - 0.013 pH of the solution) "NGA= 10x103 0.020 NO A + HU - HA+ Mach he is limiting Reagent 0.02 0.005 6.005 Neutral 0.015 Holls of MA Remain & CHAL HA= 0.03 - pH= pkat lag Csalt] => ÞH-4-97+ log [ CHA) [Acid)” 0151 10:07 PH= 4-619 The solni set Butter Buffor only webera=XN0A / because it contain plazh MGA n= 0.015 gruak acide strog talt! HA = 0.000 spects аон - 0.005 MAA - Nat+ A & spectes that you to completion 0.015 NACH Mat on J 0.005 NOOH - limiting Reagent! NaoHtHA Na A+H2O 0.005 0.02 0.005 ib. Final moles of MaA=0.005+0.015 - oor Final Molu a HA= 0.0815 pH = 4.92+ log [ 0.015] IIIIIIIIIII 50 Since it contains salt (string) weak Acid, to this son to a buffer. Applying Henderson - Hasselbasch was PH=pkat log[salt] [Acid] bg.al=pkat log [ 0.02%25] => Pka = +9.086 [0.015, pka= -log ka ka 9. axlo-lo 4) 0-IM CH3COOH CH3COOH CH3Co tut stach stat toh (1 - Rufferk PH equitualent CH3COO MA & CH3COOH will be there, not of NGOH so, svilly buffer will forn so pH=plat leg [salt] when Csalt)=[Acid (Ald] Hopka log (1) =0 Buffer Always form befor equivalene the when not af MapH i lese than Acid, so that both alcooh I CH3CO should be present [0.02) No not a buffer soll [PH=4.80