Concepts of acids and bases including HSAB, Bronsted‑Lowry and Lewis theories - Question Bank

1. Which of the following is a characteristic of a 'hard' acid in HSAB theory?
A) Large ionic radius
B) Low charge density
C) High polarizability
D) Small, highly charged cation
2. The most general definition of acids and bases is provided by the:
A) Arrhenius theory
B) Bronsted-Lowry theory
C) Lewis theory
D) Pearson's HSAB theory
3. According to the Arrhenius definition, a substance that produces OH- ions in water is a:
A) Salt
B) Acid
C) Base
D) Buffer
4. Which of the following is NOT a Bronsted-Lowry base?
A) OH-
B) NH3
C) H2O
D) BF3
5. In the reaction: NH4+ <=> NH3 + H+. NH4+ is acting as:
A) A Lewis acid
B) A Bronsted-Lowry acid
C) A Lewis base
D) A Bronsted-Lowry base
6. Which theory correctly explains the acidity of BF3?
A) Arrhenius theory
B) Bronsted-Lowry theory
C) Lewis theory
D) Oxidation state theory
7. According to the HSAB principle, stability is generally observed when:
A) Hard acids bind with soft bases
B) Soft acids bind with hard bases
C) Hard acids bind with hard bases
D) Acids and bases are of opposite hardness
8. Which of the following is a strong Lewis base?
A) BF3
B) AlCl3
C) SO3
D) PH3
9. The conjugate base of H2SO4 is:
A) HSO4-
B) SO42-
C) H3O+
D) OH-
10. Which of the following is a characteristic of a hard base?
A) Large atomic radius
B) Low charge density
C) High electronegativity
D) Readily polarizable electron cloud
11. In the reaction: CO2 + H2O <=> H2CO3, CO2 acts as a:
A) Bronsted-Lowry acid
B) Bronsted-Lowry base
C) Lewis acid
D) Lewis base
12. According to Lewis theory, the reaction between H+ and NH3 forms:
A) H2 + NH4+
B) NH4+
C) H3N+H-
D) A coordinate covalent bond
13. Which of the following metal oxides is amphoteric?
A) Na2O
B) CaO
C) Al2O3
D) SO2
14. The strength of a Bronsted-Lowry acid is related to its ability to:
A) Accept electrons
B) Donate protons
C) Accept protons
D) Donate electron pairs
15. Which of the following is a common example of a Lewis acid used in organic chemistry?
A) Water
B) Ammonia
C) Aluminum chloride
D) Sodium hydroxide
16. According to the Bronsted-Lowry definition, when HCl reacts with NaOH, which species acts as the acid?
A) HCl
B) NaOH
C) H2O
D) Cl-
17. The reaction between a Lewis acid and a Lewis base forms:
A) A salt
B) An acid anhydride
C) A complex
D) A buffer solution
18. Which of the following is a characteristic of a 'soft' species in HSAB theory?
A) High electronegativity
B) Low polarizability
C) Large size and diffuse electron cloud
D) Strong interaction with hard species
19. According to HSAB theory, which factor contributes to a species being classified as 'hard'?
A) Large size and low charge
B) Small size and high charge
C) High polarizability
D) Delocalized electrons
20. The Lewis acid-base reaction involves the formation of a coordinate covalent bond. This is also known as:
A) Proton transfer
B) Electron transfer
C) Adduct formation
D) Redox reaction
21. Which of the following species is amphoteric, meaning it can act as both an acid and a base according to Bronsted-Lowry theory?
A) HCl
B) NaOH
C) H2SO4
D) H2O
22. In the context of Lewis acids, which species can act as an acid by accepting a pair of electrons?
A) OH-
B) H2O
C) SO3
D) NH3
23. Which of the following is NOT a characteristic of a strong acid according to Arrhenius?
A) High concentration of H+ ions in water
B) Low pH
C) Ability to donate electrons
D) Good electrical conductivity in solution
24. According to Bronsted-Lowry theory, a conjugate acid-base pair differs by:
A) One electron
B) One proton
C) Two protons
D) One neutron
25. Which of the following species is a strong Lewis acid due to its vacant p-orbital?
A) H2O
B) NH3
C) BCl3
D) CH4
26. Which of the following metal ions is considered a hard acid?
A) Cu+
B) Pd2+
C) Al3+
D) Pt2+
27. In the reaction: Ag+ + 2CN- -> [Ag(CN)2]-. Silver ion (Ag+) is a soft acid and cyanide ion (CN-) is a soft base. This aligns with:
A) Arrhenius theory
B) Bronsted-Lowry theory
C) Lewis theory
D) HSAB theory
28. The principle 'Hard acids prefer to bind with hard bases and soft acids prefer to bind with soft bases' is the core of:
A) Arrhenius theory
B) Bronsted-Lowry theory
C) Lewis theory
D) HSAB theory
29. Which of the following is an example of a soft base?
A) F-
B) Cl-
C) I-
D) H2O
30. Which of the following is an example of a hard base?
A) CN-
B) OH-
C) R3P
D) R3As
31. According to HSAB theory, 'soft' bases tend to bind with:
A) Hard acids
B) Soft acids
C) Alkali metals
D) Alkaline earth metals
32. Which of the following is an example of a soft acid?
A) Li+
B) Mg2+
C) Ca2+
D) Hg2+
33. Which of the following is an example of a hard acid?
A) Ag+
B) I-
C) Na+
D) S2-
34. According to HSAB theory, 'hard' acids tend to bind with:
A) Soft bases
B) Hard bases
C) Neutral molecules
D) Cations
35. The Hard-Soft Acid-Base (HSAB) theory classifies acids and bases based on their:
A) Proton donating ability
B) Electron pair donating ability
C) Polarizability and charge density
D) Ability to dissociate in water
36. All Bronsted-Lowry bases are also Lewis bases, but the reverse is not always true. This statement is:
A) True
B) False
C) True for weak bases only
D) False for reactions in non-aqueous solvents
37. All Bronsted-Lowry acids are also Lewis acids, but the reverse is not always true. This statement is:
A) True
B) False
C) True for strong acids only
D) False for reactions in aqueous solutions
38. Which theory provides the broadest definition of acids and bases?
A) Arrhenius theory
B) Bronsted-Lowry theory
C) Lewis theory
D) All theories are equally broad
39. Which of the following is a Lewis base?
A) AlCl3
B) SO2
C) CO2
D) CN-
40. Consider the reaction: BF3 + :NH3 -> F3B:NH3. According to Lewis theory, which species acts as a Lewis base?
A) BF3
B) :NH3
C) F3B
D) NH3
41. In the Lewis theory, a base is defined as:
A) An electron pair donor
B) An electron pair acceptor
C) A proton donor
D) A proton acceptor
42. Which of the following species is a Lewis acid?
A) NH3
B) H2O
C) BF3
D) OH-
43. According to the Lewis theory, an acid is a substance that:
A) Accepts a proton
B) Donates a proton
C) Accepts an electron pair
D) Donates an electron pair
44. The conjugate base of the hydronium ion (H3O+) is:
A) H2O
B) OH-
C) H+
D) H2
45. What is the conjugate acid of water (H2O) in the Bronsted-Lowry theory?
A) OH-
B) H3O+
C) H2
D) O2
46. In the Bronsted-Lowry acid-base reaction, NH3 + H2O <=> NH4+ + OH-, which species acts as a base?
A) NH3
B) H2O
C) NH4+
D) OH-
47. Consider the reaction: HCl + H2O <=> H3O+ + Cl-. According to Bronsted-Lowry theory, which species is acting as an acid?
A) HCl
B) H2O
C) H3O+
D) Cl-
48. In the Bronsted-Lowry theory, a base is defined as:
A) An electron pair acceptor
B) A proton donor
C) A proton acceptor
D) A substance that produces H+ ions in water
49. Which of the following is a characteristic property of a base according to Arrhenius?
A) Tastes sour
B) Turns red litmus blue
C) Reacts with metals to produce hydrogen gas
D) Donates an electron pair
50. According to the Arrhenius theory, an acid is a substance that:
A) Accepts a proton
B) Donates a proton
C) Increases the concentration of hydroxide ions in aqueous solution
D) Increases the concentration of hydrogen ions in aqueous solution