Where in the lungs does gas exchange occur

Between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.