Question

For spontaneous reaction, $\Delta G$is:
(A) –ve
(B) +ve
(C) zero
(D) None of these

Answer 1

A spontaneous reaction is a chemical reaction in which there is no need for external energy to involve the reactants to convert into products.
$\Delta G$ is called the change in Gibbs free energy. Free energy is the energy offered to do work. In spontaneous reactions, free energy is going to release as it proceeds.

Complete step by step solution:
-The mathematical expression for the change in free energy of a reaction is the combination of the change in enthalpy and change in entropy.
-The mathematical expression of the change in free energy of a reaction is as follows.
$\Delta G=\Delta H-T\Delta S$
Where $\Delta G$ = change in free energy
$\Delta H$ = change in enthalpy
$\Delta S$= change in entropy
-In spontaneous reactions when the products are going to form some amount of energy is going to release.
-If the change in enthalpy is negative and change in entropy is positive then only some amount of energy is going to release in spontaneous reactions.
-Energy that is going to be released from spontaneous reactions means the free energy of a spontaneous reaction is negative.
-Therefore $\Delta G$ is negative for spontaneous reactions.

So, the correct option is A.

Note: The symbol for Gibbs free energy ‘G’ given by an American scientist Josiah Gibbs. Enthalpy is nothing but the internal energy of the system. If the energy is going to release in a spontaneous reaction means the system is losing energy then enthalpy will be negative for the spontaneous reaction. Spontaneous reactions happen with an upsurge in overall entropy, or disorderness in the reaction means entropy increases in spontaneous reactions.