Question

Measurements show that the enthalpy of a mixture of gaseous reactants increases by 215. kJ during a certain chemical reaction, which is carried out at a constant pressure. Furthermore, by carefully monitoring the volume change it is determined that -155. kJ of work is done on the mixture during the reaction.Calculate the change in energy of the gas mixture during the reaction. Round your answer to 2 significant digits.Is the reaction exothermic or endothermic?

Answer 1

Answer: The change in energy of the gas mixture during the reaction is 60 kJ. The reaction is endothermic.

Explanation:

According to first law of thermodynamics:

$\Delta E=q+w$

$\Delta E$=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}

$\Delta E=+215+(-155)kJ=60kJ$

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