Hydrogen burns to give a

Options

A. yellow flame
B. blue flame
C. pale yellow flame
D. pale blue flame

Explanation

**Step-by-Step Solution:**

1. **Understanding the Reaction**: When hydrogen burns, it reacts with oxygen in the air. The chemical equation for this reaction can be written as:
\[ 2H_2 + O_2 \rightarrow 2H_2O + \text{Energy} \]
Here, \(H_2\) represents hydrogen gas, \(O_2\) represents oxygen gas, and \(H_2O\) represents water.

2. **Identifying the Products**: The products of the combustion of hydrogen are water (H2O) and energy. This is an exothermic reaction, meaning it releases energy in the form of heat and light.

3. **Observing the Flame**: When hydrogen burns, it produces a pale blue flame. This flame can be nearly invisible in daylight conditions. If there are impurities present, such as sodium, the flame may appear yellow.

4. **Balancing the Reaction**: The balanced chemical equation for the combustion of hydrogen is:
\[ 2H_2 + O_2 \rightarrow 2H_2O \]
This equation shows that two molecules of hydrogen react with one molecule of oxygen to produce two molecules of water.

5. **Conclusion**: Therefore, when hydrogen burns, it primarily produces water and releases energy, characterized by a pale blue flame.

**Final Answer**: Hydrogen burns to give water (H2O) and energy.

---