Solid NH4NO3 is placed in a beaker containing water at 25 °C. When the solid has completely dissolved, the temperature of the solution is 23.5 °C.
- (a) Was the process exothermic or endothermic?
- (b) Was the process spontaneous?
- (c) Did the entropy of the system increase?
- (d) Did the entropy of the universe increase?
(a)
Interpretation: Considering the given reaction and its conditions it should be identified that the process is exothermic or endothermic.
Concept introduction: A process is referred to as spontaneous if the change occurs without any outside interference. The spontaneous change occurs in the direction of equilibrium.
Exothermic reaction: Exothermic reactions are those in which evolution of heat takes place during any chemical reaction. They release heat because the reactant molecules require less heat for breakage of bonds than the product molecules hence the reaction enthalpy will be negative value.
Endothermic reaction: Endothermic reactions are those in which heat is absorbed during any chemical reaction. In such type of reactions, external energy is needed hence reaction enthalpy will be positive value.
Answer to Problem 1PS
The process of dissolution of solid
Explanation of Solution
The chemical reaction is:
The change in enthalpy
(b)
Interpretation: Considering the given reaction and its conditions it should be identified that the process is spontaneous or not.
Concept introduction: A process is referred to as spontaneous if the change occurs without any outside interference. The spontaneous change occurs in the direction of equilibrium.
Exothermic reaction: Exothermic reactions are those in which evolution of heat takes place during any chemical reaction. They release heat because the reactant molecules require less heat for breakage of bonds than the product molecules hence the reaction enthalpy will be negative value.
Endothermic reaction: Endothermic reactions are those in which heat is absorbed during any chemical reaction. In such type of reactions, external energy is needed hence reaction enthalpy will be positive value.
Answer to Problem 1PS
The process of dissolution of solid
Explanation of Solution
In a spontaneous process, energy goes from being concentrated to being dispersed. The second law of thermodynamic state that a spontaneous process results in increase in entropy.
The
Hence, the process is spontaneous. Also the change in free energy for the reaction
(c)
Interpretation: Considering the given reaction and its conditions it should be identified that whether the entropy of the system increase.
Concept introduction: A process is referred to as spontaneous if the change occurs without any outside interference. The spontaneous change occurs in the direction of equilibrium.
Exothermic reaction: Exothermic reactions are those in which evolution of heat takes place during any chemical reaction. They release heat because the reactant molecules require less heat for breakage of bonds than the product molecules hence the reaction enthalpy will be negative value.
Endothermic reaction: Endothermic reactions are those in which heat is absorbed during any chemical reaction. In such type of reactions, external energy is needed hence reaction enthalpy will be positive value.
Entropy is the measure of randomness in the system. Standard entropy change in a reaction is the difference in entropy of the products and reactants.
Where,
Standard entropy change in a reaction and entropy change in the system are same.
It is the amount of arrangements possible in a system at a particular state.
Answer to Problem 1PS
The entropy of the system for the process of dissolution of
Explanation of Solution
In a spontaneous process, energy goes from being concentrated to being dispersed.
The
(d)
Interpretation: Considering the given reaction and its conditions it should be identified that the whether the entropy of the universe increase.
Concept introduction: A process is referred to as spontaneous if the change occurs without any outside interference. The spontaneous change occurs in the direction of equilibrium.
Exothermic reaction: Exothermic reactions are those in which evolution of heat takes place during any chemical reaction. They release heat because the reactant molecules require less heat for breakage of bonds than the product molecules hence the reaction enthalpy will be negative value.
Endothermic reaction: Endothermic reactions are those in which heat is absorbed during any chemical reaction. In such type of reactions, external energy is needed hence reaction enthalpy will be positive value.
Entropy is the measure of randomness in the system. Standard entropy change in a reaction is the difference in entropy of the products and reactants.
Where,
Standard entropy change in a reaction and entropy change in the system are same.
It is the amount of arrangements possible in a system at a particular state.
Answer to Problem 1PS
There is an increase in the entropy of the universe for the process of dissolution of
Explanation of Solution
The second law of thermodynamic state that a spontaneous process results in increase in entropy of the universe. The entropy of the universe is always greater than zero for a spontaneous process.
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Chapter 18 Solutions
Chemistry & Chemical Reactivity
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