How many among the following imparts colour to the Bunsen flame, when flame test is carried out?
`Ba, Mg, Ca, Be, Na, Sr,L`

Options

A. 5
B. 6
C. 7
D. 4

Answer

To determine how many of the given elements impart color to the Bunsen flame during a flame test, we will analyze each element one by one based on their known flame test colors.

### Step-by-Step Solution:

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

2. **List of Elements**: The elements provided are:
- Barium (Ba)
- Magnesium (Mg)
- Calcium (Ca)
- Beryllium (Be)
- Sodium (Na)
- Strontium (Sr)
- Lanthanum (La)

3. **Analyzing Each Element**:
- **Barium (Ba)**: Produces an apple green color in the flame test.
- **Magnesium (Mg)**: Produces a bright white flame, but it is often not visible due to its brightness.
- **Calcium (Ca)**: Produces an orange-red color in the flame.
- **Beryllium (Be)**: Does not impart any color to the flame; it is not visible in the flame test.
- **Sodium (Na)**: Produces a strong persistent yellow color in the flame.
- **Strontium (Sr)**: Produces a deep red color in the flame.
- **Lanthanum (La)**: Does not impart any color to the flame; it is not visible in the flame test.

4. **Counting the Elements that Impart Color**:
- From the analysis:
- Barium (Ba) - Yes (apple green)
- Magnesium (Mg) - Yes (bright white, but often not counted)
- Calcium (Ca) - Yes (orange-red)
- Beryllium (Be) - No
- Sodium (Na) - Yes (bright yellow)
- Strontium (Sr) - Yes (deep red)
- Lanthanum (La) - No
- The elements that impart color are: Barium, Calcium, Sodium, and Strontium. Magnesium is often not counted due to its brightness.

5. **Final Count**:
- Total elements that impart color: 5 (Barium, Calcium, Sodium, Strontium, and considering Magnesium).

### Conclusion:
The total number of elements that impart color to the Bunsen flame during the flame test is **5**.