Which of the following is a characteristic property of Lewis acids?

A. They donate electron pairs.

B. They accept electron pairs.

C. They have a full valence shell.

D. They are always gaseous in nature.

Which element is commonly used as a catalyst due to its ability to act as a Lewis acid?

A. Oxygen

B. Hydrogen

C. Boron

D. Nitrogen

What distinguishes transition metals from main group elements?

A. They have a complete d subshell.

B. They are found in the f-block of the periodic table.

C. They form coloured compounds.

D. They have a high electronegativity.

Which block of the periodic table contains elements that are filling their f orbitals?

A. s-block

B. p-block

C. d-block

D. f-block

Which of the following elements is NOT a Lewis base?

A. NH₃

B. H₂O

C. BF₃

D. OH⁻

a) Define a Lewis acid and a Lewis base, providing an example for each. [2]

b) How do Lewis acids and bases differ from the Brønsted-Lowry theory of acids and bases? [3]

a) Why are Lewis acids often referred to as electron-pair acceptors? [2]

b) Given the reaction: BF3 + NH3 -> BF3NH3, identify the Lewis acid and the Lewis base. [2]

Answer:

a) What is the significance of Lewis acids in catalysis? [3]

b) Provide an example of a reaction where a Lewis acid acts as a catalyst. [2]

a) Describe the role of Lewis acids in the formation of coloured compounds. [3]

b) Why are transition metals often associated with Lewis acid behaviour? [2]

c) Provide an example of a coloured compound formed due to the action of a Lewis acid. [2]

a) How does the concept of Lewis acids and bases help in understanding reactions beyond aqueous solutions? [3]

b) Explain the term "hard and soft acids and bases" in the context of Lewis theory. [3]

c) Why is BF3 a Lewis acid even though it doesn't have a hydrogen ion to donate? [2]

How do elements in the same group of the periodic table typically behave?

A. They have different atomic radii.

B. They have similar chemical properties.

C. They have different electron configurations.

D. They belong to different periods.

Which of the following is a general property of f-block elements?

A. They are all gases at room temperature.

B. They have low melting points.

C. They are good conductors of electricity.

D. They are all non-metals.

What role do Lewis bases play in Lewis acid-base reactions?

A. They accept protons.

B. They donate protons.

C. They accept electron pairs.

D. They donate electron pairs.

Which of the following is a reason for the importance of f-block elements?

A. They are all noble gases.

B. They play a crucial role in catalysis.

C. They are all alkaline earth metals.

D. They have low atomic numbers.

Which of the following elements is known to form coloured compounds due to d-d electron transitions?

A. Neon

B. Helium

C. Iron

D. Argon

a) What is the significance of the relation between Ka, Kb, and Kw? [3]

b) If the Ka of an acid is known, how can you determine the strength of its conjugate base? [3]

c) Describe the behaviour of water in the context of Lewis acid-base theory. [2]

a) Why are some Lewis acids also considered Brønsted-Lowry acids? Provide an example. [3]

b) How does the concept of Lewis acids help in understanding catalysis? [3]

c) What is the difference between a Lewis base and a nucleophile? [2]

a) Define a Lewis acid and a Lewis base, highlighting the key difference between them. [2]

b) Explain why AlCl3 is considered a Lewis acid. [2]

c) How does the Lewis definition of acids and bases differ from the Brønsted-Lowry definition? [3]

d) Provide an example of a reaction where water acts as a Lewis base and explain the process. [3]

a) Describe the significance of Lewis acids in industrial catalysis. [3]

b) Why is the concept of "hard" and "soft" Lewis acids and bases important in predicting reaction outcomes? [3]

c) Provide an example of a strong Lewis base and explain its behaviour in reactions. [2]

d) How can the strength of a Lewis acid be determined experimentally? [2]

a) How does the Lewis concept of acids and bases help in understanding complex formation in coordination chemistry? [3]

b) Why are transition metals often associated with Lewis acid behaviour in complex formation? [3]

c) Describe the behaviour of ammonia as a Lewis base in the formation of metal complexes. [3]

d) How does the strength of a Lewis base influence the stability of the complexes it forms? [2]