A gas decolourises bromine water but does not react with ammoniacal silver nitrate solution. The gas is

Options

A. Ethane
B. Acetylene
C. Ethylene
D. Methane

Answer

To solve the problem, we need to analyze the information given about the gas that decolorizes bromine water but does not react with ammoniacal silver nitrate solution.

### Step-by-Step Solution:

1. **Understanding the Tests:**
- **Bromine Water Test:** This test is used to identify alkenes and alkynes. When an alkene or alkyne reacts with bromine water, it decolorizes the solution due to the addition reaction where the double or triple bond reacts with bromine.
- **Ammoniacal Silver Nitrate Test (Tollens' Test):** This test is primarily used to identify aldehydes. If a substance does not react with Tollens' reagent, it suggests that the substance is not an aldehyde.

2. **Analyzing the Gas:**
- Since the gas decolorizes bromine water, it must be either an alkene or an alkyne.
- Since the gas does not react with ammoniacal silver nitrate, it cannot be an aldehyde.

3. **Identifying the Gas:**
- Alkenes (e.g., ethylene, propylene) will decolorize bromine water but do not react with Tollens' reagent.
- Alkynes (e.g., acetylene) also decolorize bromine water but are less common in gas form.
- However, since the question specifies a gas, ethylene (C2H4) is a common example of a gas that fits this description.

4. **Conclusion:**
- The gas that decolorizes bromine water but does not react with ammoniacal silver nitrate solution is **ethylene (C2H4)**.

### Final Answer:
The gas is **ethylene (C2H4)**.

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