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Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
Publisher: Cengage Learning
ISBN: 9781337399074
BuyFind

Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
Publisher: Cengage Learning
ISBN: 9781337399074

Solutions

Chapter
Section
Chapter 18, Problem 1PS
Textbook Problem

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.

  1. (a) Was the process exothermic or endothermic?
  2. (b) Was the process spontaneous?
  3. (c) Did the entropy of the system increase?
  4. (d) Did the entropy of the universe increase?

Expert Solution

(a)

Interpretation Introduction

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 NH4NO3 is endothermic.

Explanation of Solution

The chemical reaction is:

NH4NO3(s)NH4NO3(aq)

The change in enthalpy ΔH is positive for the reaction. The value of ΔH is +25.7 kJ/mol. Since the value is positive, thus the reaction is endothermic.

Expert Solution

(b)

Interpretation Introduction

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 NH4NO3 is spontaneous.

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 ΔrS° value for aqueous NH4NO3 is greater than for solid NH4NO3. Thus, there is an increase in entropy.

Hence, the process is spontaneous. Also the change in free energy for the reaction NH4NO3(s)NH4NO3(aq) is negative, which confirms the spontaneity.

Expert Solution

(c)

Interpretation Introduction

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. (ΔS°rxn) can be calculated by the following equation.

  ΔS°rxn = S°Products- S°reactants

Where,

  S°reactants is the standard entropy of the reactants

  S°Products is the standard entropy of the products

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. ΔSuniv=ΔSsys+ΔSsurr.

NH4NO3 is a solid compound that dissolves readily in water. In a spontaneous process, energy goes from being concentrated to being dispersed.

Answer to Problem 1PS

The entropy of the system for the process of dissolution of NH4NO3(s) increases.

Explanation of Solution

In a spontaneous process, energy goes from being concentrated to being dispersed.

The S° value for NH4NO3(s) is 151.08 J/Kmol and the S° value for NH4NO3(aq) is 259.8 J/Kmol. Thus, there is an increase in entropy of the system.

Expert Solution

(d)

Interpretation Introduction

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. (ΔS°rxn) can be calculated by the following equation.

  ΔS°rxn = S°Products- S°reactants

Where,

  S°reactants is the standard entropy of the reactants

  S°Products is the standard entropy of the products

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. ΔSuniv=ΔSsys+ΔSsurr.

NH4NO3 is a solid compound that dissolves readily in water. In a spontaneous process, energy goes from being concentrated to being dispersed.

Answer to Problem 1PS

There is an increase in the entropy of the universe for the process of dissolution of NH4NO3(s).

Explanation of Solution

NH4NO3 is a solid compound that dissolves readily in water. 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 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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Ch. 18.3 - Predict which substance in each pair has the...Ch. 18.3 - Calculate the standard entropy changes for the...Ch. 18.4 - Based on rH and rS, predict the spontaneity of the...Ch. 18.6 - Using values of fH and S to find rH and rS,...Ch. 18.6 - Calculate the standard free energy change for the...Ch. 18.6 - Oxygen was first prepared by Joseph Priestley...Ch. 18.6 - Determine the value of rG for the reaction C(s) +...Ch. 18.6 - Determine the value of the equilibrium constant,...Ch. 18.6 - Nitrogen and oxygen can react to form nitrogen...Ch. 18.7 - Consider the hydrolysis reactions of creatine...Ch. 18.7 - Assume the reaction A(aq) + B(aq) C(aq) +...Ch. 18.7 - The decomposition of diamond to graphite...Ch. 18.7 - It has been demonstrated that buckminsterfullerene...Ch. 18 - Solid NH4NO3 is placed in a beaker containing...Ch. 18 - Acetic acid, a weak acid, was added to a beaker...Ch. 18 - Identify the following processes as either...Ch. 18 - Identify the following processes as either...Ch. 18 - Predict whether each of the following processes...Ch. 18 - Predict whether each of the following processes...Ch. 18 - Indicate which of the following processes are...Ch. 18 - Indicate which of the following processes are...Ch. 18 - What information is needed to calculate the...Ch. 18 - What information is needed to calculate the...Ch. 18 - Calculate the entropy change that occurs when 0.50...Ch. 18 - Calculate the entropy change that occurs when 1.00...Ch. 18 - Calculate the change in entropy for a system in...Ch. 18 - Calculate the change in entropy of a system with...Ch. 18 - The third law of thermodynamics says that a...Ch. 18 - Identify trends in S values: (a) For the halogens:...Ch. 18 - Which substance has the higher entropy? 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(a) a...Ch. 18 - Use S values to calculate the standard entropy...Ch. 18 - Use S values to calculate the standard entropy...Ch. 18 - Calculate the standard entropy change for the...Ch. 18 - Calculate the standard entropy change for the...Ch. 18 - Calculate the standard entropy change for the...Ch. 18 - Calculate the standard entropy change for the...Ch. 18 - Is the reaction Si(s) + 2 Cl2(g) SiCl4(g)...Ch. 18 - Is the reaction Si(s) + 2 H2(g) SiH4(g)...Ch. 18 - Calculate S(universe) for the decomposition of 1...Ch. 18 - Calculate S(universe) for the formation of 1 mol...Ch. 18 - Classify each of the reactions according to one of...Ch. 18 - Classify each of the reactions according to one of...Ch. 18 - Using values of fH and S, calculate rG for each of...Ch. 18 - Using values of fH and S, calculate rG for each of...Ch. 18 - Using values of fH and S, calculate the standard...Ch. 18 - Using values of fH and S, calculate the standard...Ch. 18 - Using values of fG, calculate rG for each of the...Ch. 18 - Using values of fG, calculate rG for each of the...Ch. 18 - For the reaction BaCO3(s) BaO(s) + CO2(g), rG =...Ch. 18 - For the reaction TiCl2(s) + Cl2(g) TiCl4(), rG =...Ch. 18 - Determine whether the reactions listed below are...Ch. 18 - Determine whether the reactions listed below are...Ch. 18 - Heating some metal carbonates, among them...Ch. 18 - Calculate rH and rS for the reaction of tin(IV)...Ch. 18 - The ionization constant, Ka, for acetic acid is...Ch. 18 - The formation constant, Kf, for the reaction...Ch. 18 - The standard free energy change, rG, for the...Ch. 18 - The standard free energy change, rG, for the...Ch. 18 - Calculate rG at 25 C for the formation of 1.00 mol...Ch. 18 - Calculate rG at 25 C for the formation of 1.00 mol...Ch. 18 - For the synthesis of ammonia from its elements at...Ch. 18 - For the decomposition of solid calcium carbonate...Ch. 18 - Compare the compounds in each set below and decide...Ch. 18 - Using standard entropy values, calculate rS for...Ch. 18 - 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