Carbon monoxide (CO) reacts with hydrogen (H2) to form methane (CH4) and water (H2O). Upper C upper O (g) plus 3 upper H subscript 2 (g) double-headed arrow upper C upper H 4 (g) plus upper H subscript 2 upper O (g). The reaction is at equilibrium at 1,000 K. The equilibrium constant of the reaction is 3. 90. At equilibrium, the concentrations are as follows. [CO] = 0. 30 M [H2] = 0. 10 M [H2O] = 0. 020 M What is the equilibrium concentration of CH4 expressed in scientific notation? 1959 5. 9 x 10-2 0. 059 5. 9 x 102.