The number of moles of nitrogen present in one litre of air containing 12% nitrogen by volume, under standard condition, is:

Options

A. 4.75
B. 5.35
C. 12
D. 5.35 x` 10^(-3)`

Explanation

To find the number of moles of nitrogen present in one liter of air containing 12% nitrogen by volume under standard conditions, we can follow these steps:

### Step 1: Determine the volume of nitrogen in the air
Given that air contains 12% nitrogen by volume, we can calculate the volume of nitrogen in 1 liter of air.

\[ \text{Volume of nitrogen} = \frac{12}{100} \times 1 \text{ L} = 0.12 \text{ L} \]

### Step 2: Use the ideal gas law to find the number of moles
Under standard conditions (STP), 1 mole of an ideal gas occupies 22.4 liters. We can use this information to find the number of moles of nitrogen in the calculated volume.

\[ \text{Number of moles of nitrogen} = \frac{\text{Volume of nitrogen}}{\text{Volume occupied by 1 mole of gas}} = \frac{0.12 \text{ L}}{22.4 \text{ L/mol}} \]

### Step 3: Perform the calculation
Now, we can perform the calculation:

\[ \text{Number of moles of nitrogen} = \frac{0.12}{22.4} \approx 0.00536 \text{ moles} \]

This can also be expressed in scientific notation:

\[ \text{Number of moles of nitrogen} \approx 5.36 \times 10^{-3} \text{ moles} \]

### Final Answer
Thus, the number of moles of nitrogen present in one liter of air containing 12% nitrogen by volume under standard conditions is approximately **5.36 x 10^-3 moles**.

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