A cylinder of compressed gas that bears no label is supposed to contain either ethane or ethene. Combustion of the sample shows that `16 cm^(3)` of the gas require `48 cm^(3)` of oxygen for complete combustion. This shows that the gas is

Options

A. only ethane
B. only ethene
C. `1:1` mixtures of two gases
D. some unknown mixture of the two gases

Answer

To determine whether the gas in the cylinder is ethane (C2H6) or ethene (C2H4) based on the combustion reaction, we can follow these steps:

### Step 1: Understand the combustion reactions of ethane and ethene.

1. **Ethane (C2H6)**:
- The balanced combustion reaction is:
\[ C2H6 + \frac{7}{2} O2 \rightarrow 2 CO2 + 3 H2O \]
- This means 1 volume of ethane reacts with 3.5 volumes of oxygen.

2. **Ethene (C2H4)**:
- The balanced combustion reaction is:
\[ C2H4 + 3 O2 \rightarrow 2 CO2 + 2 H2O \]
- This means 1 volume of ethene reacts with 3 volumes of oxygen.

### Step 2: Analyze the given data.

- We are told that 16 cm³ of the gas requires 48 cm³ of oxygen for complete combustion.

### Step 3: Calculate the required oxygen for each gas.

1. **For Ethane**:
- From the reaction, 1 volume of ethane requires 3.5 volumes of oxygen.
- Therefore, for 16 cm³ of ethane:
\[ \text{Oxygen required} = 16 \, \text{cm}^3 \times 3.5 = 56 \, \text{cm}^3 \]

2. **For Ethene**:
- From the reaction, 1 volume of ethene requires 3 volumes of oxygen.
- Therefore, for 16 cm³ of ethene:
\[ \text{Oxygen required} = 16 \, \text{cm}^3 \times 3 = 48 \, \text{cm}^3 \]

### Step 4: Compare the oxygen requirement with the given data.

- The gas in the cylinder requires 48 cm³ of oxygen for 16 cm³ of gas.
- This matches the requirement for ethene (48 cm³) and does not match the requirement for ethane (56 cm³).

### Conclusion:

Since the gas requires 48 cm³ of oxygen for complete combustion, we conclude that the gas in the cylinder is **ethene (C2H4)**.

### Final Answer:
The gas is ethene (C2H4).

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