
(a)
Interpretation:
The circumstances in an endothermic reaction proceed spontaneously has to be identified.
Concept introduction:
Spontaneous process: A process which is initiated by itself, without the help of external energy source is called spontaneous process. All spontaneous process is associated with the decrease in free energy in the system.
Entropy: It’s is the measure of a system’s thermal energy per unit temperature that is unavailable for doing useful work. Symbol for entropy is
Entropy was also defined as the randomness or disorder of the system. Since it is thermodynamic state function it can be measured at instant, rather it was calculated as the difference in entropy of the two state, which was denoted by the symbol
Difference of exothermic and endothermic reactions:
Exothermic reaction | Endothermic reaction |
Energy is given out to the surroundings | Energy is taken in from the surroundings |
Enthalpy | Enthalpy |
Products have less energy than reactants | Products have more energy than reactants |
(b)
Interpretation:
The reason for
Concept introduction:
Entropy is a thermodynamic quantity, which is the measure of randomness in a system. The term entropy is useful in explaining the spontaneity of a process. For all spontaneous process in an isolated system there will be an increase in entropy. Entropy is represented by the letter ‘S’. It is a state function. The change in entropy gives information about the magnitude and direction of a process. The entropy changes associated with a phase transition reaction can be found by the following equation.
Where,

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Chapter 18 Solutions
General Chemistry
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