File: AcidBase. Acids and Bases, and Salts. ph and poh. (pp.153,154,164,166,292,294,296, 298)

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1 File: AcidBase. Acids and Bases, and Salts. ph and poh. (pp.153,154,164,166,292,294,296, 298) Show the conjugate acid-base pairs for the following reactions: Pa~e 153 1) C H20 ~ HC ORI Ans. First conjugate pair: C03-2 and HC03-2 Second conjugate pair: OH -I and H20 2) HCN + H20 ~ H30+ + CN-I Ans. First conjugate pair: HCN and CN-I Paee 154 3) H2S + (CH3)2NH ~ (CH3)2NH2+ + HS-I Ans. First conjugate pair: H2S and HS-I Second conjugate pair: (CH3)2NH and (CH3)2NH/ 4) HF + H20 ~ H30+ + F-I Ans. First conjugate pair: HF and F-I ~ ) HC2H302 + H20 ~ H30+ + C2H30/ Ans. First conjugate pair: HC2H302 and C2H ) HSO/ + HP04-2 ~ SO/ + H2PO/ Ans. First conjugate pair: HSO/ and SO/ Second conjugate pair: H2PO/ and HPO/ Ans. First conjugate pair: N2H/ and N2H4 Second conjugate pair: HzO and OH-I Ans. First conjugate pair: NH30H+ and NH20H Second conjugate pair: HCl and CI-1 Ans. First conjugate pair: NH3 and NH/ Second conjugate pair: N2H4 and N2H3-1 10) HN03 + H2S04 ~ H3SO/ + Ans. First conjugate pair: HN03 and N03-1 Second conjugate pair: H3S04+ and H2S04 1

2 11) HCI04 + N2H4 f-7 N2H/ + C10/ Ans. First conjugate pair: HCI04 and CIO/ Second conjugate pair: N2H5+ and N2H4 Paee What is the poh of a M NaOH solution? (b) What is the ph of the solution? Ans. (a) poh = 2 (b) ph = What is the ph of 0.01 M hydrochloric acid? Ans. ph = What is the [H30+] concentration of acetic acid whose ph is 4.0? Ans. [Hp+]= M 15. What are the H30+ and OH' concentrations of a solution prepared HCl to 9 ml of water? Assume that volumes are additive and that the 1 M by adding 1 ml HCl dissociates of 1 M completely. Ans. [H30+]= 1 x 10,1M [OR]= 1 x 10 13M 16. Find the ph of a M NaOH solution. NaOH is 100% dissociated. Ans. ph = The ph of a solution is found to be (a) What is the hydronium concentration? (b) What is the hydroxide concentration? (c) Is the solution acidic or basic? Ans. [H30+]= 3 x lo,8m (b) [OH,I]= 3.3 x lo,7m (c) Solution is slightly basic 18. A mass of 4 grams of N aoh is dissolved in water to form 500 ml of solution whose temperature is 25 C. What is the hydronium concentration in the solution? Ans. 5 x 10,I4M 19. A certain solution has ph of 3.89 at O C. Find the poh and [OH'l Hint: Kw at O C = Ans. poh = [OH'I]= x 10'12M 20. A chemist wants to make up a 50 ml solution of ph 1.25 HCI. The HCI is labeled 11.6 M. How should he f!;0 about the preparation? Ans. [H30+]= 5.62 x 10' M, 2.81 x lo'3moles HCl, 0.24 ml ofhcl with ml of water. 21. Given the K" for acetic acid (CH3COOH) to be 1.8 x 10'5, calculate the percentage dissociation of 0.5 M acetic acid. The dissociation reaction is: CH3COOH + H20 f-7 H30+ + CH3COO 1 Ans. 0.60% 2

3 22.Both HCl and NaOH are strong electrolytes. What is the ph of the solution formed by adding 40 ml of 0.10 M NaOH to 10 ml of 0.45 M HCl? NaOH is a strong base and HCl is a strong acid. Ans. ph= 2 Pa~e What is the hydronium ion concentration of a solution that has a ph of 2.6? Ans. [H30+]= 2.5 x 10-3M 24. Calculate (a) the [H30+] and (b) the ph of a 0.1 M solution ofnh/i(derived from a salt such as NH4N03). K,,= 5.6 X NH4 + + Hp f-7 Hp+ + NH3 Ans. (a) 7.5 x 1O-6M (b) ph = What is the [OH-I] of a 0.1 M NaCN? ~= 2.5 x 10-5 CN-I + H20 f-7 HCN + OH-' Ans. [OH -1]= 1.6 x 10-3M, poh = 2.8, ph = The ph of a sample of human blood was measured to be 7.41 at 25 C. Calculate the poh, [H+], and [OR] for the sample. Ans. poh = 6.59; [W] = 3.9 X 10-8 M; [OH -I] = 2.6 X 10-7 M 27. The hypochlorite ion (CIO -I) is a strong oxidizing agent often found in household bleaches and disinfectants. It is also the active ingredient that forms when swimming pool water is treated with chlorine. In addition to its oxidizing abilities, the hypochlorite ion has relatively high affinity for protons (it is a much than cr, for example) and forms the weakly acidic hypochlorous 3.5 x 10-8). Calculate the ph of a M aqueous solution of stronger base acid (HClO, K" = hypochlorous acid. Ans. ph = Calculate the H30+ ion concentration in Pepsi Cola if the ph is 2.46 Ans x Calculate the ph of a 0.1 M acetic acid solution if 1.34% of the CH3COOH molecules in this solution have ionized to form H30+ and CH3COO -I ions. CH3COOH + H20 f-7 H30+ + CH3COO-1 Ans. ph = Calculate the ph of a 0.20 M solution of HCN_ K. = 4.9 X

4 Ans. ph = 5.0 Pa2e If [H30+] = 1 x 10-5mole/ L, is the solution acidic, basic, or neutral? What is the of this solution? Ans. acidic; [OH -1]= 1 x 10-9M 32. The hydrogen ion concentration of a solution is 1 x M. What is the ph of the solution? Ans The ph of a solution is 6.0. What is the [H30+]? Ans. 1 x 10-6M ~ What is the [H30+] of a solution if the ph is 3.77 Ans. 2 x 10-4M 35. A 0.100M solution of acetic acid is only partially ionized. Using a measure of ph, the [Hp+] is calculated as 1.34 x 10"3 M. What is the acid dissociation constant CK.) of acetic acid? Ans x 10-5 Hint: [HC2HP2] at equilibrium = M 36. What is the poh if the hydrogen ion concentration is 2 x 10-7M? Ans Find the ph of a solution whose [OH -I] is 3.6 x 10"5 M. Ans Pa2e A 0.500M solution of a weak acid, HX, is only partially ionized. The [H+] was found to be 2.63 x 10-3 M. Find the dissociation constant for this acid. Ans x Calculate the acid dissociation constant of a weak monoprotic acid if a 0.5 M solution of this acid?ives a hydrogen ion concentration of O.OOOIM? Ans. 2 x 10". 40. How many equivalents are in 500 ml of a solution that has a concentration of 1 M sodium hydroxide? Ans. 0.5 equiv. 4

5 41. Detennine the hydrogen concentration ([H+]), hydroxide concentration ([OR]), ph and poh for each of the following solutions. A M HCzHPz (10.0% ionization) HCzH30Z + HzO f-7 H30+ + CZH30z'l Ans. [H+] = 1 x 10.3 M; [OH'I] = 1 X 10,11M; ph = 3; poh = 11 B M NH3 (10.0% ionization) NH3 + H.P f-7 NH/ + ORI Ans. [H+] = 1 x 10.10M; [OH I] = 1 x 10 M; ph = 10; poh = 4 C. 1.0 X 10.4 M HCN (3.5% ionization) HCN + HzO f-7 Hp+ + CN'I Ans. [H+] = 3.6 x 10,6 M; [OH'I] = 2.86 X 10-9 M; ph = 5.46; poh = 8.54 D M tartaric acid (0.042% ionization) HZC4H406 + HzO f-7 H30+ + HC4H406 1 Ans. [H+] = 7 x 10.7 M; [OH I] = 1.43 X 10.8 M; ph = 6.17; poh = 7.83 E. 1.6 X 10.3 M oxalic acid (0.166% ionization) HZCZ04 + HzO f-7 H30+ + HCzO/ Ans. [H+] = 2.66 x 10,6 M; [OH I] = 3.76 X 10.9 M; ph = 5.58; poh = 8.42 F M NH3 (0.95% ionization) NH3 + HzO f-7 NH/ + OH 1 Ans. [H+] = 1.2 x lo-izm; [OR] = 8.36 x 10.3 M; ph = 2.07; poh = What is the hydrogen ion concentration in a solution containing M benzoic acid and M sodium benzoate? Ka for benzoic acid = 6.6 x lo's.. Ans X 10'4 M 43. Calculate the ph of a solution whose hydrogen concentration is moll L. Ans What would be the ionization constant for acetic acid at 25 C if a M solution of is ionized to the extent of 1.38%? this acid Ans. 1.9 X 10.6 Pa2e What are the [~] and [ClO'I] of a M solution of HClO? K. for HClO = 3.5 x 10'8 HClO + HzO f-7 H30+ + ClO,I Ans. [H+] and [ClO.1] = x 10's 46. Calculate the ph of a 0.3 M solution of aniline, C6HsNHz. ~ for aniline 4.2 x Ans. ph = 9.05 C6HsNHz + HzO f-7 C6HsNH/ + OR 47. Complete the equations for each of the following acid-base reactions: a. HF(aq) + CH3COO.I(aq) -7 b. HzS(aq) + C03'z (aq) -7 5