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PRACTICE QUIZ KEY ACID-BASE (20 points)

PRACTICE QUIZ KEY ACID-BASE (20 points). 1. (3 pts) Predict whether the solution…. A B N a. KCN (CN- is conjugate base.) A B N b. NaNO 3 (NO 3- is anion of strong acid; not basic.) A B N c. CH 3 NH 3 Cl (CH 3 NH 3 + is similar to NH 4 + ; acidic).

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PRACTICE QUIZ KEY ACID-BASE (20 points)

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  1. PRACTICE QUIZ KEY ACID-BASE(20 points)

  2. 1. (3 pts) Predict whether the solution… • A B N a. KCN • (CN- is conjugate base.) • A B N b. NaNO3 • (NO3- is anion of strong acid; not basic.) • A B N c. CH3NH3Cl • (CH3NH3+ is similar to NH4+; acidic)

  3. 2. (3 pts) Calculate the Ka. • pH = 4.60; [H+] = 2.5 x 10-5 M • HCN W H+ + CN- Ka = [H+][CN-] / [HCN] • [H+] = [CN-] = 2.5 x 10-5 M • [HCN] = 1.5 M • Ka = (2.5 x 10-5)2/ 1.5 M = 4.2 x 10-10

  4. 3. (3 pts) Calculate the pH. • NH3 + H2O W NH4+ + OH- • Initial 0.75 0 0 • Change -x x x • Equil. 0.75 - x x x • Ignore "x" in the “0.75 – x” term because "x“ is small (insignificant) compared to 0.75!! • Kb = [NH4+][OH-]/[NH3] = 1.8 x 10-5 • Kb = x2/0.75 = 1.8 x 10-5 • x2 = 1.35 x 10-5; x = 3.7 x 10-3 M = [OH-] • pOH = -log([OH-]) = 2.43 • pH = 14 – pOH = 14 - 2.43 • pH = 11.57

  5. 4. (3 pts) Circle T (true) or F (false): • T F a. The pH of a 0.1 M solution of HNO3 is 1. • (HNO3 is a strong acid.) • T F b. The acetate ion is a stronger base than water. • T F c. The compound C5H5N is an example of a weak acid.

  6. 5. (1 pt) What is the conjugate base? • NH3W NH2- + H+ • NH2-

  7. 6. (1 pt) What is the conjugate acid? • H-(aq) + H2O(g) W H2(g) + OH-(aq) • base acid C.A. C.B. • H2

  8. 7. (4 pts) Calculate [H+]. • Kb =Kw/Ka=1.0 x 10-14/2.0 x 10-9 = 5.0 x 10-6 • BrO- + H2O W HBrO + OH- • I 0.10 M 0 0 • C -x x x • E 0.10 – x x x • Ignore "x" in the “0.10 - x" term because "x" is small (insignificant) compared to 0.10!! • Kb = [HBrO][OH-]/[BrO-] = 5.0 x 10-6 = x2/0.10 • x = 7.1 x 10-4 M = [OH-] • [H+] [OH-] = Kw = 1.0 x 10-14 • [H+] = Kw/[OH-] = 1.0 x 10-14/7.1 x 10-4 = 1.4 x 10-11M

  9. 8. (2 pts) Write an equation… • a. NaC7H5O2 (WB) BASIC • C7H5O2- + H2O W HC7H5O2 + OH- • b. HNO2 (WA) ACIDIC • HNO2W H+ + NO2-

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