There are several criteria for purity of organic compounds. Out of these which one is considered best?

Options

A. Melting point
B. Microscopic examination
C. Mixed melting point
D. colour.

Answer

To determine the best criterion for the purity of organic compounds, we can analyze the various methods available. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Criteria for Purity
There are several criteria that can be used to assess the purity of organic compounds, including color, microscopic examination, melting point, and mixed melting point.

### Step 2: Eliminate Inadequate Criteria
- **Color**: Many organic compounds can have the same color, making it an unreliable indicator of purity.
- **Microscopic Examination**: This method is not effective for organic compounds as it cannot accurately determine purity.

### Step 3: Evaluate Melting Point
- **Melting Point**: While the melting point can provide some information about purity, it is not definitive. If impurities are present, they may not significantly alter the melting point, leading to potential misinterpretation.

### Step 4: Identify the Best Criterion
- **Mixed Melting Point**: This is the most reliable method for assessing purity. When a pure compound is mixed with an impure one, the melting point of the mixture will typically decrease. This decrease indicates the presence of impurities.

### Step 5: Conclusion
Therefore, the best criterion for determining the purity of organic compounds is the mixed melting point method.

### Final Answer
The best criterion for the purity of organic compounds is the **mixed melting point**.

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