What is true regarding free radical polymerization of ethylene?

Options

A. Polymerization is invoked by either peroxide initiator or radiation
B. Polymerization is exothermic in nature
C. Molecular weight gain occur in propagation step of polymerization
D. All of these

Answer

To determine what is true regarding the free radical polymerization of ethylene, we will analyze the process step by step.

### Step 1: Understanding Free Radical Polymerization
Free radical polymerization is a type of chain reaction that involves the formation of free radicals, which are highly reactive species with unpaired electrons. Ethylene (C2H4) can undergo free radical polymerization to form polyethylene (polythene).

### Step 2: Initiation
The process begins with an initiator, which can be a peroxide or radiation. For example, benzoil peroxide (C6H5 COO) decomposes under light to generate free radicals. This step is crucial as it produces the initial free radicals that will start the polymerization process.

**Hint:** Look for substances that can generate free radicals when decomposed, such as peroxides.

### Step 3: Propagation
In the propagation step, the free radical generated in the initiation step reacts with an ethylene molecule. This reaction forms a new free radical that can further react with another ethylene molecule. This process continues, resulting in a growing polymer chain. Each addition of an ethylene molecule increases the molecular weight of the polymer.

**Hint:** Remember that in propagation, the chain grows as each new monomer (ethylene) is added to the growing polymer.

### Step 4: Termination
The polymerization process concludes with the termination step. This occurs when two free radicals combine to form a stable molecule, effectively stopping the reaction. The termination can happen in various ways, such as the combination of two growing polymer chains.

**Hint:** Think about how free radicals can neutralize each other by pairing up their unpaired electrons.

### Step 5: Evaluating Statements
Now, we can evaluate the statements provided:

1. **Polymerization is invoked by either peroxide initiator or radiation.** - This statement is true as we discussed the role of initiators.

2. **Polymerization is exothermic in nature.** - This statement is also true because the formation of bonds releases energy.

3. **Molecular weight gain occurs in the propagation step of polymerization.** - This statement is true as well since each ethylene addition increases the molecular weight of the polymer.

4. **All of these statements are correct.** - Since all previous statements are true, this statement is also correct.

### Conclusion
All statements regarding the free radical polymerization of ethylene are true.

### Final Answer
**All of the above statements are correct regarding the free radical polymerization of ethylene.**

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