Hydrolysis and condensation of a mixture of $18 mol$ of $(CH X_{3}) X_{2} SiCl X_{2}$ and $4 mol$ of $(CH X_{3}) X_{3} SiCl$ gives only linear silicone molecules of the type $(CH X_{3}) X_{3} Si - [O - Si (CH X_{3}) X_{2}] X_{n} - O - Si (CH X_{3}) X_{3}$ , all with the same chain length. The value of $n$ is

Answer: C

(CH X_{3}) X_{3} SiCl

has one Cl, so it caps a chain end; each chain needs two caps.

4 mol

of capping reagent gives

4/2 = 2 mol

of chains. The

18 mol

of difunctional

(CH X_{3}) X_{2} SiCl X_{2}

is shared among these 2 chains, so

n = 18/2 = 9