Which one of the following is the most abundant compound?

Options

A. `H_(2)O`
B. `SIO_(2)`
C. `AI_(2)O_(3)`
D. `Air`

Answer

To determine which of the given compounds is the most abundant, we will analyze each option based on their presence in the Earth's crust and atmosphere.

### Step 1: Identify the Compounds
The compounds provided in the question are:
1. H2O (Water)
2. SiO2 (Silicon Dioxide)
3. Al2O3 (Aluminum Oxide)
4. Al (Aluminum)

### Step 2: Research the Abundance of Each Compound
Next, we need to look into the abundance of each compound in the Earth's crust:

1. **H2O (Water)**: Water is essential for life and covers about 71% of the Earth's surface, but in terms of mass in the Earth's crust, it is not as abundant.

2. **SiO2 (Silicon Dioxide)**: SiO2 is a major component of the Earth's crust and is found in many minerals. It constitutes approximately 59.59% of the Earth's crust by mass.

3. **Al2O3 (Aluminum Oxide)**: Al2O3 is less abundant compared to SiO2, making up about 8.23% of the Earth's crust.

4. **Al (Aluminum)**: While aluminum is abundant in the Earth's crust, it is present in a form of compounds rather than as a free element. Its total abundance is lower compared to SiO2.

### Step 3: Compare the Percentages
Now, we will compare the percentages of each compound:
- H2O: Not significant in mass percentage in the crust.
- SiO2: Approximately 59.59%
- Al2O3: Approximately 8.23%
- Al: Lower than SiO2.

### Step 4: Conclusion
Based on the analysis, SiO2 (Silicon Dioxide) is the most abundant compound in the Earth's crust, followed by Al2O3 and then Al. Water (H2O) is abundant in terms of volume but not in mass percentage in the crust.

### Final Answer
The most abundant compound among the given options is **SiO2 (Silicon Dioxide)**.

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