How many of the following metals can be detected in the laboratory through flame test
i) Be
ii) Mg
iii) Na
iv) K
v) Ba

Answer

To determine how many of the given metals can be detected in the laboratory through a flame test, we will analyze each metal one by one based on their ability to impart color to the flame.

### Step-by-Step Solution:

1. **Identify the Metals**: The metals provided in the question are:
- Be (Beryllium)
- Mg (Magnesium)
- Na (Sodium)
- K (Potassium)
- Ba (Barium)

2. **Understand the Flame Test**: The flame test is a qualitative analysis technique used to identify the presence of certain metal ions based on the characteristic color they emit when heated in a flame.

3. **Analyze Each Metal**:
- **Beryllium (Be)**: Does not impart any color to the flame.
- **Magnesium (Mg)**: Also does not impart any color to the flame.
- **Sodium (Na)**: Imparts a golden yellow color to the flame.
- **Potassium (K)**: Imparts a lilac (purple) color to the flame.
- **Barium (Ba)**: Imparts an apple green color to the flame.

4. **Count the Detectable Metals**: From the analysis:
- Metals that can be detected: Na, K, Ba.
- Metals that cannot be detected: Be, Mg.

5. **Conclusion**: The total number of metals that can be detected through the flame test is 3 (Na, K, Ba).

### Final Answer:
**3 metals can be detected in the laboratory through flame test.**

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