Question

1. For each of the following, predict whether an aqueous solution of the salt would be acidic, basic or neutral. Explain. a. Nacis b. NaF c. NHIS d. KHCO3 e. (CH3)2NH2NO31 2. What is the pH of a solution that is 0.060 M in potassium propionate (CH3CH2COOK) and 0.085M in propionic acid (CH3CH2COOH)? The Ka for propionic acid is 1.3x10-5.5 3. Suppose you need to prepare a buffer for a pH of 10.6. An acid-base pair (HA/A') to use has the pka value of 9.8. Describe the composition of your buffer solution: (a) the star your buffer solution: (a) the starting ratio of [HA and A): (b) should strong acid or strong base be added to the HA/A-solution; (c) How much strong acid/strong base- should be added in terms of (A-1 equivalent? 4. Pyradine (C6H5N) is a weak organic base with a Kb of 1.7x10. Suppose you were to titrate 25.0 mL of a 0.100 M aqueous solution of pyridine with a 0.200 M HCl solution." (a) What is the pH at the equivalence point (when the mole of the acid added is exactly the same as the mole of the base in the solution)? (b) The Ka of the acid-base indicator 2.3 dinitrophenol is around 6.69x10-5, and the K, of the acid base indicator thymolphthalein is approximately 1.26x10-10. If you had to choose between these two indicators for your titration above, which would you choose? 5. A 25.0mL sample of a 0.20M aqueous solution of HC2H3O2S (thioglycolic acid) was titrated with 0.20 M NaOH. The pk of thioglycolic acid is 3.68. Calculate the pH after the following volumes of 0.20 M NaOH are added: (a) 10.0 mL & (b) 40.0 mL

Answer 1

pH as Salt Salution can be acidic i neutral or basic ph of salt salution. 1. Salt composed of acid - Strong & strong bose Meutral Nau I As is up of made Naon (strory boge) and nu . I strong auid ) 2. Nace → Neutral - : Naon I strong bore ) Naf a qt is salt of + HF (wcall aud) Strong base + weak acid NaF = Basic Besic salution . © Nhy I - qt is salt os Nua (weak base) + HI (strong acid) A salt of weak bost and strong acid → on acidic salt. 1. Nhy I . y Acidic {weak bose) " (CH3), NH 2 NO 3 - It is salt of (CH3)Nu. A to and HNO 3 ( strong acid). salt of weak bate & strong auid - acidic salt. - (CH3)NH₂ NO3 → Acidic salt

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