The number of moles of nitrogen present in one litre of air containing 14% nitrogen by volume, under standard condition, is:

Options

A. 1.35 x` 10^(-3)`
B. 2.35 x` 10^(-3)`
C. 5.35 x` 10^(-3)`
D. 6.25 x` 10^(-3)`

Explanation

To find the number of moles of nitrogen present in one liter of air containing 14% nitrogen by volume under standard conditions, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Volume of Nitrogen**:
- Given that the air contains 14% nitrogen by volume, we can calculate the volume of nitrogen in 1 liter of air.
- Volume of nitrogen = 14% of 1 liter = \( \frac{14}{100} \times 1 \) liter = 0.14 liters.

2. **Use the Ideal Gas Law**:
- Under standard conditions (STP), 1 mole of an ideal gas occupies 22.4 liters.
- We can use this relationship to find the number of moles of nitrogen in the calculated volume.

3. **Calculate the Number of Moles**:
- The formula to calculate the number of moles (n) is given by:
\[ n = \frac{\text{Volume of gas}}{\text{Molar volume at STP}} \]
- Substituting the values:
\[ n = \frac{0.14 \text{ liters}}{22.4 \text{ liters/mole}} \]
- Performing the calculation:
\[ n = \frac{0.14}{22.4} = 0.00625 \text{ moles} \]

4. **Express in Scientific Notation**:
- To express the number of moles in scientific notation:
\[ n = 6.25 \times 10^{-3} \text{ moles} \]

5. **Final Answer**:
- The number of moles of nitrogen present in one liter of air is \( 6.25 \times 10^{-3} \) moles.