Which of the following statement is incorrect ?

Options

A. The solution of alkali metal in liquid ammonia are strongly reducing in nature
B. `BeCl_2` is a linear molecule in vapour phase , but is polymeric in solid state
C. Calcium carbide reacts with water to give acetylene
D. Calcium is also an essential constituent of chlorophyll

Answer

To determine which of the statements provided is incorrect, we will analyze each statement one by one.

### Step 1: Analyze the first statement
**Statement 1**: "The solution of alkali metal in liquid ammonia are strongly reducing in nature."

- Alkali metals, when dissolved in liquid ammonia, produce solvated electrons that are responsible for their strong reducing properties.
- This statement is **true**.

### Step 2: Analyze the second statement
**Statement 2**: "Barium chloride is a linear molecule in vapor phase but is a polymeric in solid state."

- Barium chloride (BaCl2) does exhibit different structures in different states. In the vapor phase, it can be considered linear, while in the solid state, it forms a polymeric structure due to the presence of vacant p-orbitals that allow for coordination with neighboring chlorine atoms.
- This statement is **true**.

### Step 3: Analyze the third statement
**Statement 3**: "Calcium carbide reacts with water to give acetylene."

- Calcium carbide (CaC2) indeed reacts with water to produce acetylene (C2H2) and calcium hydroxide (Ca(OH)2).
- The reaction can be represented as:
\[ \text{CaC}_2 + 2 \text{H}_2\text{O} \rightarrow \text{C}_2\text{H}_2 + \text{Ca(OH)}_2 \]
- This statement is **true**.

### Step 4: Analyze the fourth statement
**Statement 4**: "Calcium is an essential component of chlorophyll."

- Chlorophyll primarily contains magnesium (Mg) as its central atom, not calcium. Iron (Fe) is also involved in the structure of chlorophyll but is not a central component.
- Therefore, this statement is **false**.

### Conclusion
The incorrect statement among the options is the fourth statement: "Calcium is an essential component of chlorophyll."

Thus, the correct answer is **Option 4**.

---