chem 2 exam 2

1.According to the Arrhenius concept, an acid is a substance that ________.

B) causes an increase in the concentration of H+ in aqueous solutions

2.A Bronsted-Lowry acid is defined as a substance that ________.

E) acts as a proton donor

3. Which one of the following is a Bronsted-Lowry acid?

A) (CH3)3NH+

B) CH3COOH

C) HF

D) HNO2

4. The molar concentration of hydronium ion in pure water at 25 °C is ________.

B) 1.0 × 10-7

5. Which one of the following is the weakest acid?

D) HCN (Ka = 4.9 × 10-10)

6. Given Reaction: HSO4− + H2O ⇌ SO42− + H3O+

pKa values: HSO₄⁻ = 2.0 H₃O⁺ = –1.7

ok

7. Which direction does the equilibrium favor?

the weaker acid

8. In the gas phase reaction below, NH3 is acting as a(n) ________.

C) Lewis base

9. What is the pH of an aqueous solution at 25.0 °C that contains 2.50 × 10-4 M hydronium ion?

D) 3.60

10. What is the pOH of an aqueous solution at 25.0 °C that contains 2.50 × 10-4 M hydronium ion?

D) 10.4

11. Calculate the pH of a solution at 25.0 °C that contains 2.95 × 10-12 M hydronium ions.

B) 11.53

12. A 0.22 M aqueous solution of the weak acid HA at 25.0 °C has a pH of 4.15. The value of Ka for HA is ________.

D) 2.3 × 10-8

13. The pH of a 0.25 M aqueous solution of hydrofluoric acid, HF, at 25.0 °C is 2.03. What is the value of Ka for HF?

= 3.5 × 10-4

14. What is the pH of a 0.40 M aqueous solution of N Br at 25.0 °C? Kb for NH3 is 1.8 × 10^-5

pH = - log [H+] = 4.82

15. What is the pOH of a 0.20 M aqueous solution of N Br at 25.0 °C? for N is 1.8 × .

9.02

16. Which of the following statements about salts dissolved in water is correct?

B) The conjugate acid of a weak base can react with water to produce

17. Which statement correctly describes the relationship between acid strength and 𝐾𝑎?

B) A stronger acid has a larger 𝐾𝑎.

18. Of the following, which is the strongest acid?

A) HIO4

19. Which of the following correctly matches each acid–base theory with its definition?

B) Arrhenius: produces 𝐻+or 𝑂𝐻―in aqueous solution; Brønsted–Lowry: proton donor/acceptor; Lewis: electron-pair acceptor/donor

21. The Henderson-Hasselbalch equation is ________.

C) pH = pKa + log (base/acid)

22. In a solution, when the concentrations of a weak acid and its conjugate base are equal ________.

C) the -log of the [H+] and the -log of the Ka are equal

23.Which of the following combinations can form a buffer solution?

C) CH₃COOH and CH₃COONa

24. What is the primary function of a buffer solution?

C) To resist large changes in pH when small amounts of acid or base are added

25. When does a buffer have its greatest buffering capacity?

C) When the concentrations of the weak acid and its conjugate base are approximately equal

26. A 25.0 mL sample of a solution of an unknown compound is titrated with a 0.115 M NaOH solution. The titration curve above was obtained. The unknown compound is ________.

C) a weak acid

27. A 50.0 mL sample of a solution of a monoprotic acid is titrated with a 0.115 M NaOH

solution. The titration curve above was obtained. The concentration of the monoprotic acid is

about ________ mol/L

D) 0.0600

28. The pH of a solution prepared by mixing 50.0 mL of 0.125 M NaOH and 40.0 mL of 0.125 M HNO3 is ________

E) 12.14

29. A 50.0 mL sample of an aqueous H2SO4 solution is titrated with a NaOH solution.The equivalence point is reached with of the base. The concentration of H2SO4 is

________ M

A) 0.234

30. The solubility of manganese (II) hydroxide (Mn(OH)2) is What is the Ksp of Mn(OH)2?

B) 4.3 × 10-14

31. Calculate the pH of a solution that is 0.278 M in sodium formate and in 0.222 m formic acid. The of formic acid is 1.77 × 10^-4.

A) 3.843

32. Calculate the pH of a solution that is 0.322 M in nitrous acid ( ) and 0.178 M in potassium nitrite (KNO2). The acid dissociation constant of nitrous acid is 4.50 × 10^-4

A) 3.093

33. Calculate the percent ionization of formic acid ( H) in a solution that is 0.152 M in formic acid. The pKa of formic acid is 1.77 × 10^-4

C) 3.42

34. What is the pH of a buffer solution that is 0.172 M in hypochlorous acid (HClO) and 0.131 M in sodium hypochlorite? The pKa of hypochlorous acid is 3.8 × 10^8

E) 7.30

36. What is the pH of a buffer solution that is 0.266 M in lactic acid and 0.111 M in sodium lactate? The pKa of lactic acid is 1.4 × 10^-4

D) 3.47

37. Water becomes a supercritical fluid when it is ________.

A) above both its critical temperature and critical pressure

38. Which of the following is arranged correctly in order of increasing distance from Earth's surface?

D) troposphere < stratosphere < mesosphere < thermosphere

39. Which of the following is released by the combustion of fossil fuels?

B) CO2

40. Photoionization processes (e.g., N2 + hν → N2+ + e-) remove UV of < 150 nm. Which photoreaction is the principal absorber of UV in the 150-200 nm range in the upper atmosphere

B) O2 + hν → 2O

41. The majority of ozone that protects against the high energy radiation of the sun is found in

the ______

D) stratosphere

42. Of the reactions involved in the photodecomposition of ozone (shown below), which are photochemical?

C) 1 and 3

43. Select the substance that is thought to be partially responsible for depleting the concentration of ozone in the stratosphere

A) CFCl3

45. Which gaseous sulfur compound combines with water to form the principal acidic constituent of acid rain?

B) SO3

47. Which of the following is not a stage in water treatment?

D) distillation

48. Chemical treatment of municipal water supplies commonly entails use of CaO, Al2(SO4)3, and Cl2. The purpose of adding CaO is to ________.

E) make the water slightly basic so that addition of Al2(SO4)3 will afford a gelatinous precipitate of Al(OH)3

49. Water containing high concentrations of ________ cations is called hard water.

E) Ca2+ or Mg2+

50. Nitrogen oxides catalytically destroy ozone.

true

51. Ozone depletion from chlorofluorocarbons is chiefly due to the production of free chlorine.

true

52. A faucet drips 1 drop per second. If it takes 20 drops to make 1 mL, approximately how many liters of water does this faucet waste in one week?

B) 30 L