A bromide ion does not intefere with the chromyl chloride test because when a bromide is present:

Options

A. `Br_(2)` is liberated, which leaves the NaOH solution colourless
B. `CrO_(2)Br_(2)` formed does not volatilise as `CrO_(2)Cl_(2)` does
C. `CrO_(2)Br_(2)` does not react with NaOH
D. no gaseous substance containing bromine is produced

Answer

To solve the question, we need to understand the chromyl chloride test and how bromide ions interact during this test. The chromyl chloride test is primarily used to detect chloride ions, but we need to analyze the behavior of bromide ions in this context.

**Step-by-Step Solution:**

1. **Understanding the Chromyl Chloride Test:**
- The chromyl chloride test involves the reaction of potassium dichromate (K2Cr2O7) with concentrated sulfuric acid (H2SO4). This reaction produces chromyl chloride (CrO2Cl2), which is characterized by deep red fumes.

2. **Reaction with Chloride Ions:**
- When chloride ions (Cl-) are present, they react with chromyl chloride, leading to the formation of sodium chromate (Na2CrO4) when passed through aqueous sodium hydroxide (NaOH). This indicates the presence of chloride ions.

3. **Behavior of Bromide Ions:**
- In the presence of bromide ions (Br-), a redox reaction occurs. The bromide ions are oxidized to bromine gas (Br2), while potassium dichromate is reduced to chromium ions (Cr3+).

4. **Formation of Bromine:**
- The reaction can be summarized as follows:
- 2 K2Cr2O7 + 14 H2SO4 + 6 Br- → 4 Cr3+ + 6 Br2 + 7 Na2SO4 + 7 H2O
- Here, Br- is oxidized to Br2, which is a gaseous product.

5. **Conclusion:**
- Since Br2 is produced in the presence of bromide ions, it does not interfere with the chromyl chloride test. The liberated bromine gas does not react with NaOH to produce a colored solution, thus leaving the solution colorless.

6. **Final Answer:**
- Therefore, the correct answer to the question is that when a bromide ion is present, Br2 is liberated, leaving the NaOH solution colorless.