The first step is to formulate the Kc expression. Kc is the "concentration of the products / concentration of the reactants". We show concentration is in moldm-3 by using square brackets. The molar co-efficient in the equation are the powers. So, here Kc would be: Kc = [NO2]2 / [N2O4]. This style of calculation is best with a SUE table with S being the starting moles, U being the moles used and E being the moles at equilibrium. N2O4: Starting moles, 0.0370. Used moles, -0.006. End moles, 0.0310.NO2: Starting moles, 0. Used moles, +0.012. End moles, 0.0120.These are the number of MOLES at equilibrium, but for Kc we need concentration. c=n/v, so we simply divide by the volume (0.5dm-3) to get concentrations of N2O4: 0.0620 and NO2: 0.0240. Substitute into the Kc expression we constructed before and Kc turns out to be: (0.0242)/(0.0620) = 9.29X10-3 to 3sf. Final step is to work out the units, which turn out to be simply moldm-3.