Question

Measurements show that the enthalpy of a mixture of gaseous reactants increases by 186.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 −179.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 1 significant digit. kJ Is the reaction exothermic or endothermic? exothermic endothermic

Answer 1

To begin with, as Delta H = variation in enthalpy is >0 , it means rxn is endothermic.
The rule says: Delta U = Delta H + W = 186 -179 = 7 kJ.
Where Delta U is variation in internal energy and W is the work done.