Given the balanced chemical equation for the reaction, which is the correct expression for the equilibrium constant, keq? 2 upper n subscript 2 baseline upper o subscript 5 baseline (g) double-headed arrow 4 upper n upper o subscript 2 baseline (g) + upper o subscript 2 baseline (g) k subscript e q baseline = startfraction left-bracket upper n upper o subscript 2 baseline right-bracket left-bracket upper o subscript 2 baseline right-bracket over left-bracket upper n subscript 2 baseline upper o subscript 5 baseline right-bracket endfraction k subscript e q baseline = startfraction left-bracket upper n upper o subscript 2 baseline right-bracket superscript 4 baseline left-bracket upper o subscript 2 baseline right-bracket over left-bracket upper n subscript 2 baseline upper o subscript 5 baseline right-bracket superscript 2 endfraction k subscript e q baseline = startfraction left-bracket upper n subscript 2 baseline upper o subscript 5 baseline right-bracket superscript 2 over left-bracket upper n upper o subscript 2 baseline right-bracket superscript 4 baseline left-bracket upper o subscript 2 baseline right-bracket endfraction.