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 mixture was moved from room temperature to a higher temperature, the mixture turned darker brown. Which of the following conclusions about the mixture is true? (3 points)
The forward reaction is exothermic.
The backward reaction has a negative net enthalpy.
The colorless gas has a higher enthalpy than the brown gas.
The equilibrium between the two forms of the gas is disturbed at high temperatures.