The number of moles of oxygen in 1 L of air containing 21% oxygen by volume, in standard conditions, is

Options

A. 0.186 mol
B. 0.21 mol
C. 2.10 mol
D. 0.0093 mol

Explanation

To find the number of moles of oxygen in 1 L of air containing 21% oxygen by volume at standard conditions, we can follow these steps:

### Step 1: Determine the volume of oxygen in 1 L of air
Since the air contains 21% oxygen by volume, we can calculate the volume of oxygen in 1 L of air.

\[ \text{Volume of oxygen} = 21\% \text{ of } 1 \text{ L} = \frac{21}{100} \times 1 \text{ L} = 0.21 \text{ L} \]

### Step 2: Use the molar volume of gas at standard conditions
At standard temperature and pressure (STP), the molar volume of any gas is approximately 22.4 L/mol. This means that 1 mole of gas occupies 22.4 liters.

### Step 3: Calculate the number of moles of oxygen
To find the number of moles of oxygen, we can use the formula:

\[ \text{Number of moles} = \frac{\text{Volume of gas}}{\text{Molar volume}} \]

Substituting the values we have:

\[ \text{Number of moles of oxygen} = \frac{0.21 \text{ L}}{22.4 \text{ L/mol}} \]

Calculating this gives:

\[ \text{Number of moles of oxygen} = 0.0093 \text{ moles} \]

### Final Answer
The number of moles of oxygen in 1 L of air containing 21% oxygen by volume at standard conditions is **0.0093 moles**.

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