Borax heat test is given by

Options

A. `Co^(2+)`
B. `Zn^(2+)`
C. `Cu^(2+)` ions
D. `Ni^(2+)`

Explanation

### Step-by-Step Solution:

1. **Understanding Borax**:
- Borax is a chemical compound with the formula Na2B4O7·10H2O. It contains sodium, boron, and water of crystallization.

2. **Heating Borax**:
- When borax is heated, it loses its water of crystallization, resulting in the formation of a glassy substance. The reaction can be summarized as:
\[ \text{Na}_2\text{B}_4\text{O}_7 \cdot 10\text{H}_2\text{O} \rightarrow \text{NaBO}_2 + \text{B}_2\text{O}_3 \]
- This glassy substance is known as a glass bead.

3. **Preparation of the Bead**:
- A platinum wire is dipped into the heated borax to form a bead. The borax melts and forms a glass bead that contains sodium metaborate (NaBO2) and boron oxide (B2O3).

4. **Testing for Cations**:
- The glass bead is then used to test for the presence of certain metal cations. The bead is dipped into the dry salt of the cation and then placed in a flame.

5. **Observing Flame Colors**:
- Different metal cations produce characteristic colors when heated in a flame. The cations that can be identified using the borax bead test include:
- **Cobalt (Co2+)**: Produces a blue color.
- **Copper (Cu2+)**: Produces a green color.
- **Nickel (Ni2+)**: Produces a green color.

6. **Conclusion**:
- The borax bead test is used to identify colored salts or cations that give colored flames. The cations that can be identified using this test are Cu2+, Ni2+, and Co2+.

### Final Answer:
The borax bead test is given by the cations: **Cu2+ (Copper), Ni2+ (Nickel), and Co2+ (Cobalt)**.

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