2.49g of ammonia at STP occupies a volume of 4.48 `dm^3` calculate the molar mass of ammonia.

Options

A. 24g/mol
B. 12.45g/mol
C. 27.54g/mol
D. 25.45g/mol

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 have:
- Mass of ammonia (NH₃) = 2.49 g
- Volume of ammonia at STP = 4.48 dm³ (which is equivalent to 4.48 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 in the given volume
To find the number of moles of ammonia in 4.48 L, we can use the formula:
\[ \text{Number of moles} = \frac{\text{Volume}}{\text{Molar volume at STP}} = \frac{4.48 \text{ L}}{22.4 \text{ L/mol}} \]

Calculating this gives:
\[ \text{Number of moles} = \frac{4.48}{22.4} = 0.2 \text{ moles} \]

### Step 4: Calculate the molar mass of ammonia
The molar mass (M) can be calculated using the formula:
\[ M = \frac{\text{mass}}{\text{number of moles}} \]
Substituting the values we have:
\[ M = \frac{2.49 \text{ g}}{0.2 \text{ moles}} = 12.45 \text{ g/mol} \]

### Conclusion
The molar mass of ammonia (NH₃) is 12.45 g/mol.

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