1. HF < HCl < HBr < HI : Increasing acidic strength 2. H₂O < H₂S < H₂Se < H₂Te : Increasing pK_a values 3. NH₃ < PH₃ < AsH₃ < SbH₃ : Increasing acidic character 4. CO₂ < SiO₂ < SnO₂ < PbO₂ : Increasing oxidizing power

Answer: 2. H₂O < H₂S < H₂Se < H₂Te : Increasing pK_a values Key idea: check each trend. 1: acidic strength HF < HCl < HBr < HI is correct (weaker H-X bond). 2: down the group, acidity of mathrmH₂O 3: acidic character of group 15 hydrides increases down the group: correct. 4: oxidising power rises as the +4 state becomes less stable down group 14 (inert pair effect): correct. Option 2 is the arrangement not strictly followed.

Topic: Valence, oxidation states and chemical reactivity· Classification of Elements and Periodicity in Properties

In which one of the following arrangements the given sequence is not strictly according to the properties indicated against it ?

1. \(HF < HCl < HBr < HI\) : Increasing acidic strength

2. \(H_2O < H_2S < H_2Se < H_2Te\) : Increasing \(pK_a\) values

3. \(NH_3 < PH_3 < AsH_3 < SbH_3\) : Increasing acidic character

4. \(CO_2 < SiO_2 < SnO_2 < PbO_2\) : Increasing oxidizing power

Doubtly Asked 30 Oct 2026 NEET UG 2021 Practice test neet Save WhatsApp Report

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Answer: 2. \(H_2O < H_2S < H_2Se < H_2Te\) : Increasing \(pK_a\) values

Key idea: check each trend.

1: acidic strength HF < HCl < HBr < HI is correct (weaker H-X bond).
2: down the group, acidity of \(\mathrm{H_2O
3: acidic character of group 15 hydrides increases down the group: correct.
4: oxidising power rises as the +4 state becomes less stable down group 14 (inert pair effect): correct.

Option 2 is the arrangement not strictly followed.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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In which one of the following arrangements the given sequence is not strictly according to the properties indicated against it ?

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