What is the difference in molar mass of Undecane and Dodecane?

Write about the Wurtz reaction or describe the preparation of alkanes from alkyl halides via the Wurtz reaction,including examples and its limitations.

$CH_3-CH(CH_3)-CH_3 + CH_2=CH_2 \xrightarrow[2.5^oC]{HF} (A)$; $(A)$ is:

In the bromination of isobutane,the relative reactivity rates of $1^oH, 2^oH,$ and $3^oH$ are $1 : 82 : 1600$ respectively. Calculate the percentage yield of products $(a)$ and $(b)$ in the following reaction:
$CH_3-CH(CH_3)-CH_3 (excess) + Br_2 \xrightarrow{hv} (a) CH_3-C(Br)(CH_3)-CH_3 + (b) CH_3-CH(CH_3)-CH_2Br$

The product formed in the first step of the reaction of $CH_3-CH_2-CH(Br)-CH_2-CH(Br)-CH_3$ with excess $Mg / Et_2O$ $(Et = C_2H_5)$ is

In which of the following is the rotation around the carbon-carbon bond least restricted?