The colour chage observed when excess ethyne is passed through the solution of bromine water is

Options

A. Colourless to reddish brown
B. Colourless to green
C. reddish brown to colourless
D. Pink to colourless

Answer

To solve the question regarding the color change observed when excess ethyne (acetylene) is passed through bromine water, we can follow these steps:

### Step-by-step Solution:

1. **Understanding the Reactants**:
- Ethyne (C2H2) is an alkyne, which is a type of unsaturated hydrocarbon.
- Bromine water is a solution of bromine (Br2) in water, which is typically reddish-brown in color.

2. **Reaction of Ethyne with Bromine**:
- When ethyne is passed through bromine water, a reaction occurs where the triple bond in ethyne reacts with bromine.
- This reaction results in the addition of bromine across the triple bond, forming a dibromo compound.

3. **Color Change**:
- The reddish-brown color of bromine water is due to the presence of Br2.
- As ethyne reacts with bromine, the Br2 is consumed in the reaction, leading to a decrease in its concentration in the solution.
- This consumption of bromine results in a color change from reddish-brown to colorless.

4. **Conclusion**:
- Therefore, when excess ethyne is passed through bromine water, the observed color change is from reddish-brown to colorless.

### Final Answer:
The color change observed when excess ethyne is passed through the solution of bromine water is from reddish-brown to colorless.

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