To what extent does hydrogen exist in the earth's crust ?

Explanation

**Step-by-Step Text Solution:**

1. **Understanding the Question**: The question asks about the extent to which hydrogen exists in the Earth's crust. This means we need to determine the percentage of hydrogen in the Earth's crust.

2. **Recognizing Hydrogen's Rarity**: It is important to note that hydrogen is considered a rare element in the Earth's crust. This sets the stage for understanding its abundance.

3. **Finding the Percentage**: Research and data indicate that hydrogen comprises approximately 0.15% of the total Earth's crust. This percentage reflects how much hydrogen is present in relation to other elements.

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