A salt imparts a yellow colour to a borax bead in an oxidising flame. What would be the colour of the bead in a reducing flame?

Options

A. Green
B. Blue
C. Red
D. Violet

Answer

To solve the question regarding the color of a borax bead in a reducing flame after it imparts a yellow color in an oxidizing flame, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Borax Bead Test**:
- The borax bead test is used to identify colored metal radicals in qualitative analysis. It involves heating a borax bead (sodium borate) in a flame and observing the color changes that occur when different salts are introduced.

2. **Composition of Borax**:
- Borax is chemically represented as Na2B4O7·10H2O (sodium tetraborate decahydrate). Upon heating, it loses water and becomes anhydrous sodium borate (Na2B4O7).

3. **Reactions in the Borax Bead Test**:
- When the borax is heated, it forms sodium borate (NaBO2) and boric anhydride (B2O3). The boric anhydride can react with metal oxides to form colored complexes.

4. **Color in Oxidizing Flame**:
- In an oxidizing flame, certain metal ions can impart specific colors to the borax bead. In this case, the salt gives a yellow color to the bead.

5. **Color in Reducing Flame**:
- The same salt, when tested in a reducing flame, will produce a different color. For many metal ions, the color changes due to the different oxidation states or the presence of reducing conditions.

6. **Determining the Color Change**:
- Based on the information provided, if the salt imparts a yellow color in an oxidizing flame, it is likely that in a reducing flame, the bead will change to a green color.

7. **Conclusion**:
- Therefore, the color of the borax bead in a reducing flame will be green.

### Final Answer:
The color of the bead in a reducing flame will be **green**.

---