Which of the following statements is/are wrong?

Options

A. Sulphur is estimated by Carius method as `BaSO_4`.
B. Victor Meyer's method is used for the determination of molecular mass of a non-volatile compound.
C. Kjeldahl's method is used for all nirogen-containing organic compounds.
D. Phosphorous is estimated by Carius method as `Mg(NH_4)PO_4`.

Explanation

To determine which of the statements regarding the estimation of elements and compounds are wrong, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: Sulphur is estimated by Carius method as barium sulphate.**
- The Carius method is indeed used to estimate sulfur by converting it into barium sulfate (BaSO4). This statement is correct.

2. **Statement 2: Victor Meyer’s method is used for the determination of molecular mass of a non-volatile compound.**
- The Victor Meyer method is specifically used for determining the molecular mass of volatile acids, not non-volatile compounds. Therefore, this statement is incorrect.

3. **Statement 3: Kjeldahl's method is used for all nitrogen-containing organic compounds.**
- The Kjeldahl method has limitations and cannot be used for certain nitrogen-containing compounds, such as those with nitro groups or nitrogen in a ring structure. Thus, this statement is also incorrect.

4. **Statement 4: Phosphorus is estimated by Carius method as magnesium ammonium phosphate.**
- Phosphorus is estimated by the Carius method in the form of magnesium pyrophosphate (Mg2P2O7), not magnesium ammonium phosphate. Therefore, this statement is incorrect as well.

### Conclusion:
- The wrong statements are:
- Statement 2: Victor Meyer’s method is used for the determination of molecular mass of a non-volatile compound.
- Statement 3: Kjeldahl's method is used for all nitrogen-containing organic compounds.
- Statement 4: Phosphorus is estimated by Carius method as magnesium ammonium phosphate.

### Final Answer:
The wrong statements are **2, 3, and 4**.

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