Question

Which value indicates whether a reaction is endothermic or exothermic?
A.Enthalpy change
B.Entropy change
C.Gibbs free energy change
D.Activation energy
E.Specific heat capacity

Answer 1

We know that enthalpy means the heat content of a system. It is chemically symbolized as H. The change of enthalpy $\left( {\Delta H} \right)$ is the heat energy (q) exchanged between system and surrounding at constant temperature and pressure, that is, $\Delta H = q$

Complete step by step answer:
Let’s discuss endothermic and exothermic reactions.
Endothermic reaction is the reaction in which absorption of heat takes place by system from the surroundings. The heat energy absorbed is symbolized by negative sign and enthalpy change is positive.
Exothermic reaction is the reaction in which heat energy is released to the surroundings by the system. The heat evolved in given positive signs and enthalpy change is negative.
So, we get to know that enthalpy change indicates the reaction is exothermic or endothermic.

So, the correct answer is Option A .

Additional Information:

1. Entropy is the measure of degree of randomness in a system. It is represented by the symbol S.
2. Gibbs free energy is the available amount of energy needed for resulting useful work in the conditions of constant pressure and temperature. Its symbol is G.
3. Activation energy is the minimum quantity of energy required by the reactants to undergo chemical reaction. It is represented by the symbol ${E_a}$.
4. Specific heat capacity is the heat quantity required to increase the temperature of one mole substance by one degree Celsius. It is represented by the symbol ${C_s}$.

Note:
The summation of pressure volume energy and internal energy gives the enthalpy of the system, that is, H=U+PV, where, H is enthalpy, U is internal energy and PV is pressure volume work. Both internal energy and enthalpy are state functions.