While testing borate, green edged flame is due so formation of (a) _____.

Answer

To solve the question regarding the green-edged flame observed while testing borate, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Borate Test**: The question refers to the borax bead test, which is used to detect colored cations. In this test, borax (sodium borate) is heated.

2. **Heating Borax**: When borax is heated on a platinum loop, it swells into a white porous mass. Upon further heating, this mass melts into a transparent glass bead.

3. **Reaction with Sulfuric Acid**: When sodium borate (Na2B2O7) reacts with sulfuric acid (H2SO4), it forms boric acid (H3BO3) and sodium sulfate (Na2SO4):
\[ \text{Na}_2\text{B}_2\text{O}_7 + \text{H}_2\text{SO}_4 \rightarrow \text{H}_3\text{BO}_3 + \text{Na}_2\text{SO}_4 \]

4. **Formation of Triethyl Borate**: The boric acid can react with alcohol (commonly ethanol, C2H5OH) to form triethyl borate (C2H5)3B:
\[ \text{H}_3\text{BO}_3 + 3 \text{C}_2\text{H}_5\text{OH} \rightarrow \text{(C}_2\text{H}_5)_3\text{B} + 3 \text{H}_2\text{O} \]

5. **Green Flame Production**: The triethyl borate burns with a characteristic green flame. This is the key observation that leads to the answer.

6. **Final Answer**: Therefore, the green-edged flame observed while testing borate is due to the formation of **triethyl borate (or trialkyl borate)**.

### Answer: (a) Triethyl borate (or trialkyl borate)

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