How many molecules of `O_(2)` are present in 1 L air containing 80% volume of `O_(2)` at STP?

Explanation

To find out how many molecules of \( O_2 \) are present in 1 L of air containing 80% volume of \( O_2 \) at STP, we can follow these steps:

### Step 1: Determine the volume of \( O_2 \) in 1 L of air
Since the air contains 80% volume of \( O_2 \), we can calculate the volume of \( O_2 \) in 1 L (1000 mL) of air.

\[ \text{Volume of } O_2 = 80\% \text{ of } 1000 \text{ mL} = \frac{80}{100} \times 1000 \text{ mL} = 800 \text{ mL} \]
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