# DBT JRF 2022 — Question 39

Exam: DBT JRF 2022 · Section: B · Topic: Biochemistry › Chemical Bonds & Intermolecular Forces · Difficulty: Medium

## Question

Arrange the following chemical bonds/interactions in the order of their strengths in vacuum - Hydrogen bond, Covalent bond, van der Waals attraction and Ionic bond:

## Options

- **A.** Covalent bond > Ionic bond > hydrogen bond > van der Waals attraction
- **B.** Ionic bond > Covalent bond > hydrogen bond > van der Waals attraction
- **C.** Covalent bond > Ionic bond > van der Waals attraction > hydrogen bond
- **D.** Ionic bond > Covalent bond > van der Waals attraction > hydrogen bond

## Answer

Option A

## Explanation

Ranking of bond strengths (in vacuum): Approximate bond energies: • Covalent bonds: ~200–500 kJ/mol (e.g., C-C = 347 kJ/mol, C=C = 614 kJ/mol) • Ionic interactions: ~250 kJ/mol (in vacuum; much weaker in aqueous solution due to dielectric screening) • Hydrogen bonds: ~12–29 kJ/mol per bond • Van der Waals interactions: ~0.1–10 kJ/mol per contact Order in vacuum: Covalent > Ionic > Hydrogen bonds > van der Waals In water: Ionic interactions are greatly weakened ( $\sim \frac{1}{\varepsilon_r}$ where $\varepsilon_r \approx 80$ for water), often comparable to or weaker than multiple hydrogen bonds collectively. Answer: Covalent > Ionic > Hydrogen bonds > Van der Waals (in vacuum, as typically listed in biochemistry textbooks).

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