TRB PG Assistant - Concepts of acids and bases including HSAB, Bronsted‑Lowry and Lewis theories Online Test (MCQ Quiz)

1. 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

2. 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

3. 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

4. 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-

5. 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-

6. What is the conjugate acid of water (H2O) in the Bronsted-Lowry theory?

A) OH- B) H3O+ C) H2 D) O2

7. The conjugate base of the hydronium ion (H3O+) is:

A) H2O B) OH- C) H+ D) H2

8. 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

9. Which of the following species is a Lewis acid?

A) NH3 B) H2O C) BF3 D) OH-

10. 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

11. 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

12. Which of the following is a Lewis base?

A) AlCl3 B) SO2 C) CO2 D) CN-

13. 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

14. 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

15. 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

16. 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

17. According to HSAB theory, 'hard' acids tend to bind with:

A) Soft bases B) Hard bases C) Neutral molecules D) Cations

18. Which of the following is an example of a hard acid?

A) Ag+ B) I- C) Na+ D) S2-

19. Which of the following is an example of a soft acid?

A) Li+ B) Mg2+ C) Ca2+ D) Hg2+

20. According to HSAB theory, 'soft' bases tend to bind with:

A) Hard acids B) Soft acids C) Alkali metals D) Alkaline earth metals

21. Which of the following is an example of a hard base?

A) CN- B) OH- C) R3P D) R3As

22. Which of the following is an example of a soft base?

A) F- B) Cl- C) I- D) H2O

23. 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

24. 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

25. Which of the following metal ions is considered a hard acid?

A) Cu+ B) Pd2+ C) Al3+ D) Pt2+

26. Which of the following species is a strong Lewis acid due to its vacant p-orbital?

A) H2O B) NH3 C) BCl3 D) CH4

27. According to Bronsted-Lowry theory, a conjugate acid-base pair differs by:

A) One electron B) One proton C) Two protons D) One neutron

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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-

36. 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

37. 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

38. Which of the following metal oxides is amphoteric?

A) Na2O B) CaO C) Al2O3 D) SO2

39. According to Lewis theory, the reaction between H+ and NH3 forms:

A) H2 + NH4+ B) NH4+ C) H3N+H- D) A coordinate covalent bond

40. In the reaction: CO2 + H2O <=> H2CO3, CO2 acts as a:

A) Bronsted-Lowry acid B) Bronsted-Lowry base C) Lewis acid D) Lewis base

41. 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

42. The conjugate base of H2SO4 is:

A) HSO4- B) SO42- C) H3O+ D) OH-

43. Which of the following is a strong Lewis base?

A) BF3 B) AlCl3 C) SO3 D) PH3

44. 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

45. Which theory correctly explains the acidity of BF3?

A) Arrhenius theory B) Bronsted-Lowry theory C) Lewis theory D) Oxidation state theory

46. 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

47. Which of the following is NOT a Bronsted-Lowry base?

A) OH- B) NH3 C) H2O D) BF3

48. According to the Arrhenius definition, a substance that produces OH- ions in water is a:

A) Salt B) Acid C) Base D) Buffer

49. 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

50. 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

Concepts of acids and bases including HSAB, Bronsted‑Lowry and Lewis theories - Online Test

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