The active mass of 7.0 g of nitrogen in a 2.0 L container would be

Options

A. 0.25
B. 0.125
C. 0.5
D. `14.0`

Answer

To find the active mass of 7.0 g of nitrogen in a 2.0 L container, we will follow these steps:

### Step 1: Calculate the number of moles of nitrogen
The number of moles (n) can be calculated using the formula:

\[ n = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]

Given:
- Mass of nitrogen = 7.0 g
- Molar mass of nitrogen (N₂) = 28 g/mol

Substituting the values:

\[ n = \frac{7.0 \, \text{g}}{28 \, \text{g/mol}} = 0.25 \, \text{moles} \]

### Step 2: Calculate the active mass (concentration) of nitrogen
The active mass (or concentration) is defined as the number of moles of the substance divided by the volume of the container in liters:

\[ \text{Active mass} = \frac{\text{number of moles}}{\text{volume (L)}} \]

Given:
- Number of moles = 0.25 moles
- Volume = 2.0 L

Substituting the values:

\[ \text{Active mass} = \frac{0.25 \, \text{moles}}{2.0 \, \text{L}} = 0.125 \, \text{mol/L} \]

### Conclusion
The active mass of 7.0 g of nitrogen in a 2.0 L container is **0.125 mol/L**.

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