Question

What‌ ‌is‌ ‌delta‌ ‌G?‌

Answer 1

H is defined as the enthalpy of the system or it can also be defined as the change in the total energy of the system. S denotes the change in entropy. The temperature at which equilibrium is given by the division of enthalpy with the change in entropy.

Complete answer:
Every chemical change that is happening in this world, as big as that happening in factories to as small as that happening in our body, involves a change in free energy.
This change in free energy is defined as $\Delta G = \Delta H - T\Delta S$
Now this equation can be explained as the subtraction of the entropy multiplied by the then temperature from the total energy of the system. The temperature has to be in kelvin.
This is also known as the standard free energy change between the system and the surrounding. It is defended in $\dfrac{{kJ}}{{mol}}$ under standard pH, temperature and pressure conditions. The standard pH is $7.0$ in biological systems, ${25^ \circ }C$ and ten kilopascals.
There can be reactions of different type: -
Exothermic reaction
These reactions which after the completion of the whole reaction releases an amount of energy so as to stabilise the reaction. The change in free energy for this reaction is always negative.
Endothermic reaction
These are the type of reactions which during the course of the reaction absorb heat for the reaction to actually happen. These reactions require some energy for the particles to interact and react. These reactions have a positive free energy change.
Equilibrium
This is the state in which the reaction neither goes in the forward direction nor goes in the backward reaction, it is stable. The change in free energy for this reaction is zero.
$\Delta G$ is defined as the change in free energy of a system.

Note:
The temperature at which equilibrium for a system or reaction occurs is calculated by ${T_{eq}} = \dfrac{{\Delta H}}{{\Delta S}}$.