Assertion: The amphoteric behaviour of water is explained by Lewis acid-base theory. Reason: Water acts as acid with…

Step 1 — Evaluate Assertion: The amphoteric behaviour of water is explained by Bronsted-Lowry theory (proton donor/acceptor), NOT Lewis acid-base theory. Lewis theory deals with electron pair donation/acceptance. Assertion is FALSE ✗

Step 2 — Evaluate Reason:

• Water + $\mathrm{NH_3}$: $\mathrm{H_2O + NH_3 \rightleftharpoons OH^- + NH_4^+} \rightarrow$ water donates $\mathrm{H^+} \rightarrow$ acts as acid ✓
• Water + $\mathrm{H_2S}$: $\mathrm{H_2O + H_2S \rightleftharpoons H_3O^+ + HS^-} \rightarrow$ water accepts $\mathrm{H^+} \rightarrow$ acts as base ✓ Reason is TRUE ✓

Answer: Option (4) — Assertion false, Reason true