3.49g of ammonia at STP occupies a volume of 2.48 `dm^3` calculate the molar mass of ammonia.

Explanation

To calculate the molar mass of ammonia (NH₃) given that 3.49 g of ammonia occupies a volume of 2.48 dm³ at STP (Standard Temperature and Pressure), follow these steps:

### Step 1: Understand the conditions at STP
At STP, one mole of any ideal gas occupies a volume of 22.4 liters.

### Step 2: Convert the volume from dm³ to liters
Since 1 dm³ is equal to 1 liter, we can directly state that:
- Volume of ammonia = 2.48 dm³ = 2.48 liters.

### Step 3: Use the relationship between mass, volume, and molar mass
We know that:
- Molar mass (M) = (mass of gas (m) / volume of gas (V)) × molar volume at STP (22.4 L).

### Step 4: Substitute the known values into the equation
We have:
- Mass of ammonia (m) = 3.49 g,
- Volume of ammonia (V) = 2.48 L,
- Molar volume at STP = 22.4 L.

Using the formula:
\[ M = \left( \frac{3.49 \, \text{g}}{2.48 \, \text{L}} \right) \times 22.4 \, \text{L} \]

### Step 5: Calculate the molar mass
Now, perform the calculation:
\[ M = \left( \frac{3.49}{2.48} \right) \times 22.4 \]
\[ M = 1.40645 \times 22.4 \]
\[ M \approx 31.5 \, \text{g/mol} \]

### Conclusion
The molar mass of ammonia (NH₃) is approximately **31.5 g/mol**.

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