In multimolecular colloidal solutions , atoms or molecules are held together by :

Options

A. (a)H-bonding
B. (b)Vander-Waals forces
C. (c)Ionic bonding
D. (d)Polar covalent bonding

Answer

To solve the question regarding the forces holding atoms or molecules together in multimolecular colloidal solutions, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Colloidal Solutions**:
- Colloidal solutions consist of particles that are larger than simple molecules but smaller than those in a suspension. The size of the solute particles in colloidal solutions typically ranges from 1 nanometer (nm) to 1000 nanometers.

2. **Identifying Types of Colloids**:
- There are different types of colloids, one of which is the multimolecular colloid. In multimolecular colloids, small particles (which can be less than 1 nm) aggregate to form larger particles.

3. **Nature of Forces in Multimolecular Colloids**:
- The particles in multimolecular colloids are held together by weak interactions. These interactions can include van der Waals forces, which are weak attractive forces between molecules.

4. **Evaluating the Options**:
- The question provides several options: hydrogen bonding, van der Waals forces, ionic bonding, and polar covalent bonding.
- Among these, hydrogen bonding and ionic bonding are stronger than van der Waals forces. Polar covalent bonding involves sharing electrons between atoms, which is not applicable in this context.

5. **Conclusion**:
- Since multimolecular colloids are formed by the aggregation of small particles held together by weak forces, the correct answer is that they are held together by **van der Waals forces**.

### Final Answer:
- The correct option is **B: van der Waals forces**.