The density in grams per litre of ethylene `(C_(2)H_(4))` at `STP` is :-

Options

A. `1.25`
B. `2.50`
C. `3.75`
D. `5.25`

Explanation

To find the density of ethylene (C₂H₄) at Standard Temperature and Pressure (STP), we will follow these steps:

### Step 1: Determine the molar mass of ethylene (C₂H₄)
- The molecular formula of ethylene is C₂H₄, which consists of:
- 2 carbon (C) atoms: Each carbon has an atomic mass of approximately 12 g/mol.
- 4 hydrogen (H) atoms: Each hydrogen has an atomic mass of approximately 1 g/mol.

Calculating the molar mass:
\[ \text{Molar mass of C₂H₄} = (2 \times 12) + (4 \times 1) = 24 + 4 = 28 \text{ g/mol} \]

### Step 2: Use the volume of one mole of gas at STP
- At STP, one mole of any ideal gas occupies a volume of 22.4 liters.

### Step 3: Calculate the density
- Density (D) is defined as mass (m) divided by volume (V):
\[ D = \frac{m}{V} \]
- Here, the mass of one mole of ethylene is 28 g, and the volume is 22.4 L.
\[ D = \frac{28 \text{ g}}{22.4 \text{ L}} \]

### Step 4: Perform the calculation
\[ D = \frac{28}{22.4} \approx 1.25 \text{ g/L} \]

### Conclusion
The density of ethylene (C₂H₄) at STP is approximately **1.25 g/L**.

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