Water can be tested by

Options

A. smell
B. taste
C. hydrated `CuSO_(4)`
D. anhydrous `CoCl_(3)` (blue) which changes to pink

Answer

To determine how water can be tested, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Water**:
- Water is chemically represented as H₂O. It is a colorless, odorless, and tasteless liquid in its pure form. Therefore, sensory tests (taste and smell) are not reliable methods for testing water.

2. **Using Anhydrous Copper Sulfate**:
- Anhydrous copper sulfate (CuSO₄) is a white powder. When water is added to it, it undergoes a chemical reaction to form hydrated copper sulfate (CuSO₄·5H₂O), which is blue in color. This color change indicates the presence of water.

3. **Using Anhydrous Cobalt(II) Chloride**:
- Anhydrous cobalt(II) chloride (CoCl₂) is another compound that can be used to test for water. It is blue in color when dry. Upon the addition of water, it changes to cobalt(II) chloride hexahydrate (CoCl₂·6H₂O), which is pink. This color change also indicates the presence of water.

4. **Conclusion**:
- Therefore, the presence of water can be tested using anhydrous copper sulfate or anhydrous cobalt(II) chloride, as both substances exhibit a distinct color change when they come into contact with water.

### Final Answer:
Water can be tested by using anhydrous copper sulfate or anhydrous cobalt(II) chloride, as both will change color in the presence of water.

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