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 an essential constituent of chlorophyll

Answer

To solve the question of which statement is incorrect, we will analyze each of the four statements provided:

1. **Statement 1**: "The solution of alkali metal in liquid ammonia is strongly reducing in nature."
- Alkali metals, when dissolved in liquid ammonia, form a deep blue solution due to the presence of ammoniated electrons. These electrons are highly reactive and make the solution a strong reducing agent. Thus, this statement is **correct**.

2. **Statement 2**: "Beryllium chloride is a linear molecule in vapor phase whereas a polymeric in solid state."
- In the vapor phase, beryllium chloride (BeCl2) exists primarily as a dimer (Be2Cl4), not as a linear molecule. In the solid state, it forms a polymeric structure. Therefore, the claim that it is linear in the vapor phase is **incorrect**.

3. **Statement 3**: "Calcium carbide reacts with water to give acetylene."
- Calcium carbide (CaC2) reacts with water to produce acetylene (C2H2) and calcium hydroxide (Ca(OH)2). This reaction is well-known and accurate. Therefore, this statement is **correct**.

4. **Statement 4**: "Calcium is an essential constituent of chlorophyll."
- This statement is **incorrect** because magnesium (Mg) is the essential constituent of chlorophyll, not calcium. Therefore, this statement is also incorrect.

After analyzing all four statements, we find that **Statement 2** is incorrect regarding the nature of beryllium chloride in the vapor phase.

### Final Answer:
The incorrect statement is **Statement 2**: "Beryllium chloride is a linear molecule in vapor phase whereas a polymeric in solid state."