Hydrogen burns in air to form ____ .

Explanation

To solve the question "Hydrogen burns in air to form ____", we can follow these steps:

### Step 1: Identify the Reactants
- The question mentions that hydrogen burns in air. The primary component of air that reacts with hydrogen is oxygen (O2). Therefore, the reactants in this reaction are hydrogen gas (H2) and oxygen gas (O2).

**Hint:** Think about what components of air are involved in combustion reactions.

### Step 2: Write the Chemical Reaction
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