What is the difference in molar masses of third and fourth homologues of alkane series?

Identify product ' B ' in the following sequence of reactions.

$$ \text { 1,2-Dibromoethane } \xrightarrow[\text { alcohol }]{\mathrm{KOH}} A \xrightarrow{\text { sodamide }} B $$

Identify the product ' Z ' in the following series of reactions.

The reaction of aryl halide with sodium metal in dry ether to give biphenyl is known as