Alkyl substituted chlorosilane, `R_n SiCl_((4-n))`, on hydrolysis and then condensation polymerisation yield silicones What is the value of n is the alkyl substituted chlorosilane used for the preparation of cross linked silicone.

Explanation

To solve the problem of determining the value of \( n \) in the alkyl substituted chlorosilane \( R_n SiCl_{(4-n)} \) that is used for the preparation of cross-linked silicones, we can follow these steps:

### Step 1: Understand the structure of alkyl substituted chlorosilane
The general formula for alkyl substituted chlorosilane is \( R_n SiCl_{(4-n)} \). Here, \( R \) represents an alkyl group, \( n \) is the number of alkyl groups attached to silicon, and \( 4-n \) is the number of chlorine atoms attached to silicon.

### Step 2: Identify the hydrolysis reaction
When the chlorosilane undergoes hydrolysis, the chlorine atoms are replaced by hydroxyl (–OH) groups. The hydrolysis of \( R_n SiCl_{(4-n)} \) can be represented as:
\[ R_n SiCl_{(4-n)} + H_2O \rightarrow R_n Si(OH)_{(4-n)} + HCl \]

### Step 3: Determine the number of hydroxyl groups
After hydrolysis, if \( n = 1 \), we have:
\[ R_1 SiCl_3 \]
Upon hydrolysis, this will yield:
\[ RSi(OH)_{3} \]

### Step 4: Analyze the condensation polymerization
The next step is condensation polymerization, where the hydroxyl groups can react with each other to form siloxane bonds (Si-O-Si). For \( RSi(OH)_{3} \), the three hydroxyl groups can condense with other silanol groups to form a network structure:
\[ RSi(OH)_{3} + RSi(OH)_{3} \rightarrow RSi-O-SiR + H_2O \]

### Step 5: Conclude the value of \( n \)
In order to achieve a cross-linked silicone structure, we need at least one alkyl group (R) and the presence of three hydroxyl groups for the formation of siloxane bonds. Thus, the value of \( n \) that allows for cross-linking is:
\[ n = 1 \]

### Final Answer
Therefore, the value of \( n \) for the alkyl substituted chlorosilane used for the preparation of cross-linked silicone is:
\[ n = 1 \]

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