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MCQEasyJEE 2026Group 17 Elements

JEE Chemistry 2026 Question with Solution

Given below are two statements:

Statement I: The increasing order of boiling point of hydrogen halides is HCl<HBr<HI<HF\text{HCl} < \text{HBr} < \text{HI} < \text{HF}. Statement II: The increasing order of melting point of hydrogen halides is HCl<HBr<HF<HI\text{HCl} < \text{HBr} < \text{HF} < \text{HI}.

In the light of the above statements, choose the correct answer from the options given below:

  • A

    Statement I is true but Statement II is false

  • B

    Both Statement I and Statement II are false

  • C

    Both Statement I and Statement II are true

  • D

    Statement I is false but Statement II is true

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: Two statements about the boiling point and melting point orders of hydrogen halides are given.

Find: Which statement is true and which is false.

Step 1: Boiling points Boiling point depends on intermolecular forces. HF shows strong hydrogen bonding, so it has the highest boiling point. Among HCl, HBr, HI, boiling point increases with molecular mass.

HCl<HBr<HI<HF\text{HCl} < \text{HBr} < \text{HI} < \text{HF}

So, Statement I is true.

Step 2: Melting points Melting point trends are irregular due to lattice packing. The actual order is:

HCl<HF<HBr<HI\text{HCl} < \text{HF} < \text{HBr} < \text{HI}

The given order

HCl<HBr<HF<HI\text{HCl} < \text{HBr} < \text{HF} < \text{HI}

is incorrect. So, Statement II is false.

Therefore, the correct option is A.

Concept-Based Explanation

Given: Orders of boiling point and melting point for hydrogen halides.

Find: Evaluate both statements using intermolecular forces and solid-state packing ideas.

Boiling points mainly follow the strength of intermolecular attraction. HF forms strong hydrogen bonds, which makes its boiling point exceptionally high. For HCl, HBr, and HI, dispersion forces increase with size and mass, so the boiling point rises down the group.

HCl<HBr<HI<HF\text{HCl} < \text{HBr} < \text{HI} < \text{HF}

Hence, Statement I is true.

Melting points do not always follow the same simple trend because they depend strongly on crystal lattice packing in the solid state. For hydrogen halides, the observed increasing order is:

HCl<HF<HBr<HI\text{HCl} < \text{HF} < \text{HBr} < \text{HI}

Therefore, the stated order for melting point is wrong, so Statement II is false.

Hence, the correct answer is Statement I is true but Statement II is false, that is, option A.

Common mistakes

  • Assuming boiling point and melting point must follow the same order is incorrect. Boiling point depends mainly on intermolecular forces in the liquid phase, while melting point depends strongly on crystal packing in the solid state. Evaluate them separately.

  • Ignoring hydrogen bonding in HF leads to a wrong boiling point trend. HF has unusually strong intermolecular attraction, so it does not fit the simple mass-based order used for HCl, HBr, and HI.

  • Using only molecular mass to decide the melting point order is wrong. Melting points can show irregular behavior because lattice arrangement and packing efficiency also matter. Use the actual observed order instead of extrapolating blindly.

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