Which of the following statements is false?

Options

A. HCl molecule has one sigma bond
B. Acetylene molecule has three pi bonds and three sigma bonds
C. Ethylene molecule has five sigma bonds and one pi bond
D. Water molecule has two sigma bonds and two lone pairs

Answer

To determine which of the statements is false, we will analyze each statement regarding the bonding in the specified molecules.

### Step-by-Step Solution:

1. **Analyze Statement 1: "SCl molecule has a sigma bond."**
- In the SCl molecule (sulfur monochloride), the bond between sulfur (S) and chlorine (Cl) is a single covalent bond.
- A single covalent bond consists of one sigma bond.
- **Conclusion:** This statement is true.

2. **Analyze Statement 2: "Acetylene has three pi bonds and three sigma bonds."**
- Acetylene (C2H2) has a linear structure where two carbon atoms are connected by a triple bond.
- A triple bond consists of one sigma bond and two pi bonds.
- Therefore, in acetylene, there are:
- 1 sigma bond between the two carbon atoms,
- 2 pi bonds between the two carbon atoms.
- Additionally, there are 2 sigma bonds between each carbon and hydrogen atom.
- Total sigma bonds = 1 (C≡C) + 2 (C-H) = 3 sigma bonds.
- Total pi bonds = 2 (C≡C).
- **Conclusion:** This statement is false because it incorrectly states that there are three pi bonds.

3. **Analyze Statement 3: "There are 5 sigma bonds and 1 pi bond in a certain molecule."**
- This statement is vague without specifying the molecule, but it could refer to a molecule like ethylene (C2H4) or another compound.
- If we assume it refers to a molecule with multiple single bonds and one double bond, it could be true.
- **Conclusion:** This statement is likely true, but we need more context to confirm.

4. **Analyze Statement 4: "A water molecule has 2 sigma bonds and 2 lone pairs."**
- The water molecule (H2O) has two hydrogen atoms bonded to the oxygen atom.
- The bonding structure consists of:
- 2 sigma bonds (one for each H-O bond).
- Oxygen has two lone pairs of electrons.
- **Conclusion:** This statement is true.

### Final Conclusion:
The false statement is **Statement 2**, which claims that acetylene has three pi bonds and three sigma bonds. In reality, acetylene has 3 sigma bonds and 2 pi bonds.

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