Novolac on heating with formaldehyde undergoes ___________ to form an infusible solid mass called ____________ .

Options

A. a. polymerisation , melamine
B. b. vulcanisation , resin
C. c. cross-linking, bakelite
D. d. condensation, polystyrene

Answer

To solve the question, we need to identify the process that Novolac undergoes when heated with formaldehyde and the resulting product formed.

### Step-by-Step Solution:

1. **Understanding Novolac Formation**:
- Novolac is formed through a condensation reaction between phenol and formaldehyde. This reaction can occur in the presence of an acidic or basic medium, leading to the formation of a polymer.

2. **Heating Novolac with Formaldehyde**:
- When Novolac is heated with formaldehyde, it undergoes a specific type of reaction. This reaction involves the formation of cross-links between the polymer chains.

3. **Identifying the Type of Reaction**:
- The process that Novolac undergoes when heated with formaldehyde is known as **cross-linking**. This is where the polymer chains are interconnected, resulting in a three-dimensional network.

4. **Resulting Product**:
- The product formed from this cross-linking process is an infusible solid mass known as **Bakelite**. Bakelite is a type of thermosetting plastic that is hard and heat-resistant due to its cross-linked structure.

5. **Final Answer**:
- Therefore, Novolac on heating with formaldehyde undergoes **cross-linking** to form an infusible solid mass called **Bakelite**.

### Complete Answer:
Novolac on heating with formaldehyde undergoes **cross-linking** to form an infusible solid mass called **Bakelite**.