Which salt is colourless?

Options

A. `KMnO_(4)`
B. `BaSO_(4)`
C. `NaCrO_(4)`
D. `CoCl_(2)`

Explanation

To determine which salt is colorless among the given options, we can analyze each salt one by one based on their known colors.

### Step-by-Step Solution:

1. **Identify the Salts**: The salts we need to consider are:
- Potassium permanganate (KMnO4)
- Barium sulfate (BaSO4)
- Sodium chromate (Na2CrO4)
- Cobalt chloride (CoCl2)

2. **Examine the Color of Each Salt**:
- **Potassium permanganate (KMnO4)**: This salt is known for its deep purple color due to the presence of manganese in a high oxidation state.
- **Barium sulfate (BaSO4)**: This salt is known to be colorless. It is often used as a radiocontrast agent in medical imaging.
- **Sodium chromate (Na2CrO4)**: This salt is typically yellow in color due to the chromate ion.
- **Cobalt chloride (CoCl2)**: In its anhydrous form, cobalt chloride is blue. However, when hydrated (as in CoCl2·6H2O), it appears pink or violet-blue.

3. **Conclusion**: After examining the colors of each salt, we find that:
- Potassium permanganate is purple.
- Barium sulfate is colorless.
- Sodium chromate is yellow.
- Cobalt chloride is blue (anhydrous) or pink/violet-blue (hydrated).

Thus, the only colorless salt among the options is **Barium sulfate (BaSO4)**.

### Final Answer:
The colorless salt is **Barium sulfate (BaSO4)**.

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