Choose the correct option regarding bond enthalpy of following: Column-A [bond] Column-B [bond enthalpy kJ / mol ] (a) C - C (p) 240 (b) Si - Si (q) 260 (c) Ge - Ge (r) 297 (d) Sn - Sn (s) 348

( a - s ) ; ( b - r ) ; ( c - q ) ; ( d - p )

( a - p ) ; ( b - q ) ; ( c - r ) ; ( d - s )

( a - p ) ; ( b - r ) ; ( c - q ) ; ( d - s )

( a - r ) ; ( b - s ) ; ( c - q ) ; ( d - p )

Phosphine is generally prepared in the laboratory by

heating white phosphorus with an aqueous solution of caustic soda.

heating phosphorus in a current of hydrogen.

decomposition of P 2 H 4 at 110 ° C .

heating red phosphorus with an aqueous solution of caustic soda.

What is inert pair effect?

The inert pair effect is the reluctance of s electrons of the outermost shell to participate in bonding. This is due to the poor screening effect of the d and f orbitals. This effect is observed among the p -block elements, due to which the lower oxidation state (two units less than the group oxidation state) becomes more stable for heavier elements in each group. For example in Pb , + 2 oxidation state is more predominant than the + 4 oxidation state.