Arrhenius Bronsted Lowry and Lewis Concepts - UNSOLVED PRACTICE SET

Q7. Compare the Arrhenius and Brønsted-Lowry concepts of acids and bases. Why is the Brønsted-Lowry concept considered more general?

Q8. Define Lewis acids and Lewis bases with two examples each. Why is the Lewis concept considered the most general of all acid-base concepts?

Q9. Identify the Lewis acid and Lewis base in the following reactions:

(a) Ag⁺ + 2NH₃ → [Ag(NH₃)₂]⁺

(b) CO₂ + OH⁻ → HCO₃⁻

Q10. Explain why NH₃ is a Brønsted base but not an Arrhenius base. Can NH₃ act as a Lewis base? Explain.

Q11. In the reaction HCl + NH₃ → NH₄⁺ + Cl⁻, identify the conjugate acid-base pairs. Which species is the conjugate acid and which is the conjugate base?

Q12. A student claims that all Brønsted acids are Lewis acids, but not all Lewis acids are Brønsted acids. Is the student correct? Explain with examples.

Q13. (a) Define acids and bases according to the Arrhenius, Brønsted-Lowry, and Lewis concepts.

(b) For each concept, give one example of a substance that is classified as an acid by that concept but NOT by the other two concepts.

(c) Arrange the three concepts in order of increasing generality and explain your reasoning.

Q14. (a) Explain the concept of conjugate acid-base pairs with suitable examples. What is the relationship between the strength of an acid and its conjugate base?

(b) For the following species, write their conjugate acids and conjugate bases:

H₂O, HCO₃⁻, NH₃, HSO₄⁻, OH⁻

(c) A strong acid has a weak conjugate base, and a weak acid has a strong conjugate base. Explain this statement with examples.

Q15. (a) Explain why BF₃ is a Lewis acid but not a Brønsted acid. Draw the structure showing how BF₃ accepts an electron pair from NH₃.

(b) CO₂ can react with water to form carbonic acid, but CO₂ is also considered a Lewis acid. Explain both aspects.

(c) In the Indian context, explain the role of Lewis acid-base interactions in:

(i) The formation of complexes in traditional water purification using alum

(ii) The coagulation of milk during paneer making

Q16. Consider the following equilibria and identify the acid, base, conjugate acid, and conjugate base in each case according to the Brønsted-Lowry concept:

(a) H₂SO₄ + H₂O ⇌ H₃O⁺ + HSO₄⁻

(b) HSO₄⁻ + H₂O ⇌ H₃O⁺ + SO₄²⁻

(c) NH₃ + H₂O ⇌ NH₄⁺ + OH⁻

(d) H₂O + H₂O ⇌ H₃O⁺ + OH⁻

For each reaction, also identify which species acts as a Lewis acid and which as a Lewis base, if applicable.

Q17. The following table lists various substances. Classify each as an Arrhenius acid/base, Brønsted-Lowry acid/base, Lewis acid/base, or any combination. Give reasons for your classification:

Q18. In Indian agriculture, soil pH management is crucial for crop growth:

(a) Acidic soils (pH < 6) are often treated with lime (CaO). Write the Brønsted-Lowry acid-base reaction that occurs when lime is added to acidic soil containing H⁺ ions.

(b) Some fertilisers like ammonium sulphate make the soil acidic. Explain this using the Brønsted-Lowry concept, considering the hydrolysis of NH₄⁺.

(c) Aluminium salts (Al³⁺) are sometimes present in acidic soils and can be toxic to plants. Explain why Al³⁺ acts as a Lewis acid in soil chemistry and how it affects plant roots.

(d) A farmer tests two soil samples: Sample A has pH 5.5 and Sample B has pH 7.5. Which sample requires treatment and why? Calculate the ratio of H⁺ ion concentrations in the two samples.