For the homogeneous reaction :

$4{\mathrm{NH}}_3+5{\mathrm{O}}_2\rightleftharpoons 4\mathrm{NO}+6{\mathrm{H}}_2\mathrm{O}$

The equilibrium constant ${\mathrm{K}}_{\mathrm{c}}$ has the units of:

For the homogeneous reaction,

 $4{\mathrm{NH}}_3+5{\mathrm{O}}_2\rightleftharpoons 4\mathrm{NO}+6{\mathrm{H}}_2\mathrm{O}$ the equilibrium constant, ${\mathrm{K}}_{\mathrm{c}}$ has the units 

${\text{ Conc. }}^{\mathrm{\Delta n}}={\text{ Conc. }}^{(4+6)-(4+5)}={\text{ Conc. }}^{+1}$