3.49g of ammonia at STP occupies a volume of 3.49 `dm^3` calculate the molar mass of ammonia.

Explanation

To calculate the molar mass of ammonia (NH₃) using the given data, we can follow these steps:

### Step 1: Understand the given data
We are given:
- Mass of ammonia (NH₃) = 3.49 g
- Volume of ammonia at STP = 3.49 dm³ (which is equivalent to 3.49 L)

### Step 2: Use the molar volume of a gas at STP
At Standard Temperature and Pressure (STP), one mole of any ideal gas occupies 22.4 L.

### Step 3: Calculate the number of moles of ammonia
To find the number of moles (n) of ammonia, we can use the formula:
\[ n = \frac{\text{Volume of gas at STP}}{\text{Molar volume at STP}} \]
Substituting the values:
\[ n = \frac{3.49 \, \text{L}}{22.4 \, \text{L/mol}} = 0.1558 \, \text{mol} \]

### Step 4: Calculate the molar mass of ammonia
The molar mass (M) can be calculated using the formula:
\[ M = \frac{\text{Mass of gas}}{\text{Number of moles}} \]
Substituting the values:
\[ M = \frac{3.49 \, \text{g}}{0.1558 \, \text{mol}} \approx 22.4 \, \text{g/mol} \]

### Conclusion
The molar mass of ammonia (NH₃) is approximately 22.4 g/mol.

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