*i think it’s either the first one or the last one, but i’m just not sure. nitrogen dioxide gas is dark brown in color and remains in equilibrium with dinitrogen tetroxide gas, which is colorless. 2no2(g) ⇌ n2o4(g) when the light brown color equilibrium mixture was moved from room temperature to a lower temperature, the mixture turned lighter brown in color. which of the following conclusions about this equilibrium mixture is true? this reaction is endothermic because the system shifted to the left on cooling. this reaction is endothermic because the system shifted to the right on cooling. this reaction is exothermic because the system shifted to the left on cooling. this reaction is exothermic because the system shifted to the right on cooling.