On burning hydrogen in air, the colour of flame is — Hydrocarbons Chemistry Question

💡 Solution & Explanation

I don't see the options (A, B, C, D) in your question. However, I can provide the complete answer: **When hydrogen burns in air, the flame is PALE BLUE (or almost colorless/invisible).** **Reasoning:** 1. **Combustion reaction:** $2H_2 + O_2 \rightarrow 2H_2O$ 2. **Why pale blue?** Hydrogen burns with a pale blue flame because: - The combustion is a highly exothermic reaction - The energy is primarily released as **heat** rather than visible light - The flame appears pale blue due to minimal excited electron transitions in the products - The flame is almost **invisible in daylight** but becomes pale blue in darkness 3. **Key distinction:** Unlike other fuels (e.g., carbon burns with yellow/orange flame due to incandescent particles), hydrogen produces mostly water vapor and releases energy mainly as heat, not luminous radiation. **If option B states "pale blue" or "colorless/invisible," then B is correct.** Other options stating yellow, orange, or bright colors would be incorrect.