74. which two temperatures are identical for the same substance?
(a) melting point, freezing point
b) melting point, boiling point
c) freezing point, boiling point
d) freezing point, condensation point

(A) melting point, freezing point.

Explanation:

For the same substance: when matter is transitioning from solid to liquid (melting) or liquid to solid (freezing), its temperature is fixed at the melting/freezing point, which is the same temperature.

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.