Answer: The change in energy of the gas mixture during the reaction is 60 kJ. The reaction is endothermic.
Step-by-step explanation:
According to first law of thermodynamics:

=Change in internal energy
q = heat absorbed or released
w = work done or by the system
w = work done on the system
w = -155 kJ
q = +215kJ {Heat absorbed by the system is positive}

As the heat is absorbed and enthalpy increases, the reaction is endothermic.