Chemistry & Chemical Reactivity
Chemistry & Chemical Reactivity
10th Edition
ISBN: 9781337399074
Author: John C. Kotz, Paul M. Treichel, John Townsend, David Treichel
Publisher: Cengage Learning
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Textbook Question
Chapter 18, Problem 1PS

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?

(a)

Expert Solution
Check Mark
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.

(b)

Expert Solution
Check Mark
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.

(c)

Expert Solution
Check Mark
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.

(d)

Expert Solution
Check Mark
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

Ch. 18.7 - Prob. 1.2ACPCh. 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 - Prob. 5PSCh. 18 - Predict whether each of the following processes...Ch. 18 - Indicate which of the following processes are...Ch. 18 - Prob. 8PSCh. 18 - Prob. 9PSCh. 18 - Prob. 10PSCh. 18 - Prob. 11PSCh. 18 - Calculate the entropy change that occurs when 1.00...Ch. 18 - Prob. 13PSCh. 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? (a) dry...Ch. 18 - Which substance has the higher entropy? (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 - Prob. 44PSCh. 18 - The standard free energy change, rG, for the...Ch. 18 - Prob. 46PSCh. 18 - Calculate rG at 25 C for the formation of 1.00 mol...Ch. 18 - Prob. 48PSCh. 18 - Prob. 49PSCh. 18 - Prob. 50PSCh. 18 - Compare the compounds in each set below and decide...Ch. 18 - Using standard entropy values, calculate rS for...Ch. 18 - About 5 billion kilograms of benzene, C6H6, are...Ch. 18 - Hydrogenation, the addition of hydrogen to an...Ch. 18 - Is the combustion of ethane, C2H6, product-favored...Ch. 18 - Prob. 56GQCh. 18 - When vapors from hydrochloric acid and aqueous...Ch. 18 - Calculate S(system), S(surroundings), and...Ch. 18 - Methanol is now widely used as a fuel in race...Ch. 18 - The enthalpy of vaporization of liquid diethyl...Ch. 18 - Calculate the entropy change, rS, for the...Ch. 18 - Using thermodynamic data, estimate the normal...Ch. 18 - Prob. 63GQCh. 18 - When calcium carbonate is heated strongly, CO2 gas...Ch. 18 - Sodium reacts violently with water according to...Ch. 18 - Yeast can produce ethanol by the fermentation of...Ch. 18 - Elemental boron, in the form of thin fibers, can...Ch. 18 - Prob. 68GQCh. 18 - Prob. 69GQCh. 18 - Estimate the boiling point of water in Denver,...Ch. 18 - The equilibrium constant for the butane ...Ch. 18 - A crucial reaction for the production of synthetic...Ch. 18 - Calculate rG for the decomposition of sulfur...Ch. 18 - Prob. 74GQCh. 18 - A cave in Mexico was recently discovered to have...Ch. 18 - Wet limestone is used to scrub SO2 gas from the...Ch. 18 - Sulfur undergoes a phase transition between 80 and...Ch. 18 - Calculate the entropy change for dissolving HCl...Ch. 18 - Some metal oxides can be decomposed to the metal...Ch. 18 - Prob. 80ILCh. 18 - Prob. 81ILCh. 18 - Prob. 82ILCh. 18 - Titanium(IV) oxide is converted to titanium...Ch. 18 - Cisplatin [cis-diamminedichloroplatinum(II)] is a...Ch. 18 - Prob. 85ILCh. 18 - Explain why each of the following statements is...Ch. 18 - Decide whether each of the following statements is...Ch. 18 - Under what conditions is the entropy of a pure...Ch. 18 - Prob. 89SCQCh. 18 - Consider the formation of NO(g) from its elements....Ch. 18 - Prob. 91SCQCh. 18 - The normal melting point of benzene, C6H6, is 5.5...Ch. 18 - Prob. 93SCQCh. 18 - For each of the following processes, predict the...Ch. 18 - Heater Meals are food packages that contain their...Ch. 18 - Prob. 96SCQCh. 18 - Prob. 97SCQCh. 18 - Prob. 98SCQCh. 18 - Iodine, I2, dissolves readily in carbon...Ch. 18 - Prob. 100SCQCh. 18 - Prob. 101SCQCh. 18 - Prob. 102SCQCh. 18 - Prob. 103SCQCh. 18 - Prob. 104SCQCh. 18 - The Haber-Bosch process for the production of...Ch. 18 - Prob. 106SCQCh. 18 - Prob. 107SCQ
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