Which of the following are true?

Options

A. van der waals forces are reponsible for the formation of molecular crytals
B. Branching lower the boiling points of isomeric organic due to decrease in van der waals forces
C. In graphite, van der waal forces act between the carbon layers
D. In diamond, van der waal forces act between the carbon layers

Answer

To determine which of the statements regarding chemical bonding and molecular interactions are true, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: Van der Waals forces are responsible for the formation of molecular crystals.**
- **Analysis:** Van der Waals forces are indeed weak intermolecular forces that play a significant role in the formation of molecular crystals. These forces allow molecules to aggregate and form a solid structure. Therefore, this statement is **true**.

2. **Statement 2: Branching lowers the boiling point of isomeric organic compounds due to a decrease in Van der Waals forces.**
- **Analysis:** In branched isomers, the surface area is reduced compared to their straight-chain counterparts. This reduction in surface area leads to weaker Van der Waals forces between the molecules, resulting in a lower boiling point for branched isomers. Hence, this statement is also **true**.

3. **Statement 3: In graphite, Van der Waals forces act between carbon layers.**
- **Analysis:** Graphite consists of layers of carbon atoms arranged in a hexagonal lattice. The layers are held together by Van der Waals forces, which allow them to slide over each other easily. This characteristic is what makes graphite a good lubricant and conductor of electricity. Thus, this statement is **true**.

4. **Statement 4: In diamond, Van der Waals forces act between layers.**
- **Analysis:** Diamond has a tetrahedral structure where each carbon atom is covalently bonded to four other carbon atoms, forming a very strong three-dimensional network. There are no layers in diamond like in graphite, and thus, Van der Waals forces do not act between layers in diamond. Therefore, this statement is **false**.

### Summary of Statements:
- Statement 1: True
- Statement 2: True
- Statement 3: True
- Statement 4: False

### Final Conclusion:
The true statements are 1, 2, and 3. Statement 4 is false.

---