Question

measurements show that the enthalpy of a mixture of gaseous reactants increases by 140. 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 165. 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 3 significant digits. is the reaction exothermic or endothermic? exothermic endothermic

Explanation:

Step1: Recall first law of thermodynamics

$\Delta U = q + w$
At constant pressure, $q = \Delta H$. Since enthalpy increases, $\Delta H = +140$ kJ. Work done on the system: $w = +165$ kJ.

Step2: Calculate ΔU

$\Delta U = 140 + 165 = 305$ kJ

Step3: Determine reaction type

Positive $\Delta H$ means endothermic.

Answer:

305 kJ
endothermic