The bond length of the $C-H$ bond in ethene is ...... $pm$.

Select the suitable reagent for the conversion shown below:

$^{14}CH_2=CH-CH_3 \xrightarrow[\text{or high temp}]{\text{low conc of } Br_2} (?)$
Product of the above reaction is

Cyclopentene on treatment with alkaline $KMnO_4$ gives

Identify the major product for the following reaction:

The reaction conditions used for converting $1, 2$-dibromoethane to ethylene are: