The number of moles of nitrogen present in one litre of air containing 18% nitrogen by volume, under standard condition, is:

Options

A. 4.03 x `10^(-3)`
B. 8.03 x `10^(-3)`
C. 3.08 x `10^(-3)`
D. 8.33 x `10^(-3)`

Explanation

To find the number of moles of nitrogen present in one liter of air containing 18% nitrogen by volume under standard conditions, we can follow these steps:

### Step 1: Determine the volume of nitrogen in one liter of air.
Given that the air contains 18% nitrogen by volume, we can calculate the volume of nitrogen in one liter of air.

\[ \text{Volume of nitrogen} = \text{Total volume} \times \left(\frac{\text{Percentage of nitrogen}}{100}\right) \]

\[ \text{Volume of nitrogen} = 1 \, \text{L} \times \left(\frac{18}{100}\right) = 0.18 \, \text{L} \]

### Step 2: Use the ideal gas law to find the number of moles.
At standard temperature and pressure (STP), one mole of an ideal gas occupies 22.4 liters. We can use this information to find the number of moles of nitrogen in 0.18 liters.

\[ \text{Number of moles} = \frac{\text{Volume of nitrogen}}{\text{Volume occupied by one mole at STP}} \]

\[ \text{Number of moles} = \frac{0.18 \, \text{L}}{22.4 \, \text{L/mol}} \]

### Step 3: Calculate the number of moles.
Now we perform the calculation:

\[ \text{Number of moles} = \frac{0.18}{22.4} \approx 0.00803 \, \text{moles} \]

### Step 4: Express the result in scientific notation.
To express this in scientific notation:

\[ 0.00803 \, \text{moles} = 8.03 \times 10^{-3} \, \text{moles} \]

### Conclusion:
The number of moles of nitrogen present in one liter of air containing 18% nitrogen by volume under standard conditions is approximately \( 8.03 \times 10^{-3} \, \text{moles} \).

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