Answer:
Option B
Explanation:
Increasing order of stability
(a) $[Cu(NH_{3})_{4}]^{2+}< [Cu(en)_{2}]^{2+}<[Cu(trien)]^{2+}$
Their formation of entropy increases in the same order. Ligand denticity is increased
(b) $[{Fe(H_{2}O})_{6}]^{3+}< [Fe(NO_{2})_{6}]^{3-}<[Fe(NH_{3})_{6}]^{3+}$
$\because$ NH3 is weaker ligand than NO2-
$\therefore$ The correct stability order is
$[{Fe(H_{2}O})_{}]^{3+} <[Fe(NH_{3})_{6}]^{3+}<[Fe(NO_{2})_{6}]^{3-}$
(c) $[{Co(H_{2}O})_{6}]^{3+} <[Rh(H_{2}O)_{6}]^{3+}<[Ir(H_{2}O)_{6}]^{3+}$
Zeff value increases from Co3+ to Ir3+
(d) $[{Cr(NH_{3}})_{6}]^{+} <[Cr(NH_{3})_{6}]^{2+}<[Cr(NH_{3})_{6}]^{3+}$
O.S of Cr atom increases from +1 to +3
