Chemistry
Chemistry
13th Edition
ISBN: 9781259911156
Author: Raymond Chang Dr., Jason Overby Professor
Publisher: McGraw-Hill Education
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Chapter 17, Problem 17.71QP

Consider the reaction

N 2 ( g ) + O 2 ( g ) 2 NO ( g )

Given that ΔG° for the reaction at 25°C is 173.4 kJ/mol, (a) calculate the standard free energy of formation of NO, and (b) calculate KP of the reaction. (c) One of the starting substances in smog formation is NO. Assuming that the temperature in a running automobile engine is 1100°C, estimate KP for the above reaction. (d) As farmers know, lightning helps to produce a better crop. Why?

(a)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

The standard free energy ΔG° value should be derived given nitric oxide formation reaction at 25°C.

Concept Introduction:

Thermodynamics is the branch of science that relates heat and energy in a system.  The four laws of thermodynamics explain the fundamental quantities such as temperature, energy and randomness in a system.  Entropy is the measure of randomness in a system.  For a spontaneous process there is always a positive change in entropy.  Free energy (Gibbs free energy) is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter G.  All spontaneous process is associated with the decrease of free energy in the system.  In non-spontaneous reaction there is an increase of free energy in the system.

Free energy(ΔG0): In thermodynamics free energy or Gibbs free energy is the energy that is used to express the total energy content of a system.  According to second law of thermodynamics, in all spontaneous process is associated with the decrease in free energy of the system.  That is the change in free energy will be negative.

Free energy (Gibbs free energy) is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter G. All spontaneous process is associated with the decrease of free energy in the system.  The standard free energy change (ΔG°rxn) is the difference in free energy of the reactants and products in their standard state.

ΔG°rxn=nΔGf°(Products)-nΔGf°(Reactants)

Explanation of Solution

The equilibrium constant is related to the to the standard free energy change by the given equation (1).

N2(g)+O2(g)2NO(g)ΔG=-RTlnK-------------[1]We rewrite the above equationΔG=GivenvaluesProduct=173.4KJ/mol2(2NOProduct)ΔG=86.7kJ/mol

(b)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

The equilibrium constant Kp value should be calculated for given reaction.

Concept Introduction:

Free energy (Gibbs free energy) is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter G.  All spontaneous process is associated with the decrease of free energy in the system.  The standard free energy change (ΔG°rxn) is the difference in free energy of the reactants and products in their standard state.

ΔG°rxn=nΔGf°(Products)-nΔGf°(Reactants)

Where, "n" is the number of moles

The calculate the standard free (ΔGf0) value for given reaction is shown below,

ΔG0=-RTlnK---------[1]ΔG=Free energyΔG0=Standardstate free energyR=GasConstant(0.08314 (or) 8.314.atm/K.atm)T=Temprature273KK=EqulibriumConstant(KPandKC)

Explanation of Solution

First calculate the equilibrium constant (Kp) value for given reaction

N2(g)+O2(g)2NO(g)ΔGf0=-RTlnK-------------[1]HereR=0.08314J/K.mol (or) -8.314J/K.molSubstitutedfor(Kp,RandT)valuesareequation(1)Given the values 173.4KJ/mol173.4×103J/mol=(8.314J/K.mol)(298K)lnKpRewrite the above equation (1)lnKp=ΔG0-RT=173.4×103J/mol)(8.314J/Kmol)(298K)lnKp=ΔG0-RT=173.4×103)(2477.572)lnKp = -69.99Kp=e69.99Kp=4.0×1031

Given NO formation reaction equilibrium constant value is 4.0×1031

(c)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

The nitric oxide starting formation has to determine.

Concept Introduction:

Thermodynamics is the branch of science that relates heat and energy in a system.  The four laws of thermodynamics explain the fundamental quantities such as temperature, energy and randomness in a system.  Entropy is the measure of randomness in a system.  For a spontaneous process there is always a positive change in entropy. Free energy (Gibbs free energy) is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter G.  All spontaneous process is associated with the decrease of free energy in the system.  The equation given below helps us to calculate the change in free energy in a system.

ΔG = ΔΗ- TΔS

Where,

ΔG  is the change in free energy of the system

ΔΗ is the change in enthalpy of the system

T is the absolute value of the temperature

ΔS is the change in entropy in the system

Explanation of Solution

 We calculate the enthalpy changes for given reaction

N2(g)+O2(g)2NO(g)HereStandard enthalpy changes equation InK2K1=ΔH0R(T2-T1T1×T2)[1]ΔH°totalno.ofproductformationΔHfo(NO)The equilibrium values of NO= 86.7kJ/molΔHfo(NO)=2(86.7kJ/mol)=173.4kJ/molTherespactivevaluesaresubstitutedequation(1)InK24.0×10-31=173.4×103J/mol8.314J/molK(1373K-298K(1373)(298K))InK24.0×10-31=173.4J/mol8.314J/molK(1075K409154K)InK24.0×10-31=(208563.86)(2.672×10-3K)InK24.0×10-31=5572.82KK2=3×10-7

(d)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

The lighting helps to produce a better crop, the reason behind this has to explained. 

Concept Introduction:

Thermodynamics is the branch of science that relates heat and energy in a system.  The four laws of thermodynamics explain the fundamental quantities such as temperature, energy and randomness in a system.  Entropy is the measure of randomness in a system.  For a spontaneous process there is always a positive change in entropy.  Free energy (Gibbs free energy) is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter G.  All spontaneous process is associated with the decrease of free energy in the system.  In non-spontaneous reaction there is an increase of free energy in the system.

Non-spontaneous reaction: This type of reaction explain as, endergonic reaction (mean by heat absorption non-spontaneous process) or unfavourable reaction in a chemical reaction in which the standard change in free energy is positive and energy is absorbed.

Explanation of Solution

The lighting promotes the formation of NO (from N2 and O2 in the air), which eventually leads to the formation of nitrate ions (NO3) as essential nutrition for plants.

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Chapter 17 Solutions

Chemistry

Ch. 17.5 - Prob. 2RCFCh. 17.5 - Prob. 3RCFCh. 17.5 - Prob. 4RCFCh. 17.6 - Calculate the equilibrium constant (KP) for the...Ch. 17.6 - Prob. 7PECh. 17.6 - Prob. 8PECh. 17.6 - A reaction has a positive H and a negative S.Is...Ch. 17.6 - For the reaction A(g)+B(g)C(g) G = 33.3 kJ/mol at...Ch. 17.6 - For the reaction C(aq)A(aq)+B(aq) G = 1.95 kJ/mol...Ch. 17 - Explain what is meant by a spontaneous process....Ch. 17 - State which of the following processes are...Ch. 17 - Prob. 17.3QPCh. 17 - Define entropy. 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Given...Ch. 17 - The Ksp of AgCl is given in Table 16.2. What is...Ch. 17 - Prob. 17.55QPCh. 17 - Water gas, a mixture of H2 and CO, is a fuel made...Ch. 17 - Consider the following Brnstead acid-base reaction...Ch. 17 - Crystallization of sodium acetate from a...Ch. 17 - Prob. 17.59QPCh. 17 - A certain reaction is spontaneous at 72C. If the...Ch. 17 - Predict whether the entropy change is positive or...Ch. 17 - 17.62The reaction NH3(g)+HCl(g)NH4Cl(s) proceeds...Ch. 17 - Prob. 17.63QPCh. 17 - The molar heat of vaporization of ethanol is 39.3...Ch. 17 - Prob. 17.65QPCh. 17 - In the Mond process for the purification of...Ch. 17 - Calculate G and KP for the following processes at...Ch. 17 - Calculate the pressure of O2 (in atm) over a...Ch. 17 - Prob. 17.69QPCh. 17 - Prob. 17.70QPCh. 17 - Consider the reaction N2(g)+O2(g)2NO(g) Given that...Ch. 17 - Prob. 17.72QPCh. 17 - Prob. 17.73QPCh. 17 - Prob. 17.74QPCh. 17 - Prob. 17.75QPCh. 17 - Prob. 17.76QPCh. 17 - Prob. 17.77QPCh. 17 - Prob. 17.78QPCh. 17 - Prob. 17.79QPCh. 17 - Prob. 17.80QPCh. 17 - Prob. 17.81QPCh. 17 - Prob. 17.82QPCh. 17 - Prob. 17.83QPCh. 17 - Prob. 17.84QPCh. 17 - Shown here are the thermodynamic data for ethanol:...Ch. 17 - The reaction shown here is spontaneous at a...Ch. 17 - Consider two carboxylic acids (acids that contain...Ch. 17 - Many hydrocarbons exist as structural isomers,...Ch. 17 - Use the thermodynamic data in Appendix 2 to...Ch. 17 - A rubber band is stretched vertically by attaching...Ch. 17 - One of the steps in the extraction of iron from...Ch. 17 - Derive the equation G=RTln(Q/K) where Q is the...Ch. 17 - The sublimation of carbon dioxide at 78C is...Ch. 17 - Entropy has sometimes been described as times...Ch. 17 - Referring to Figure 17.1, we see that the...Ch. 17 - A student looked up the Gf, Hf, and S values for...Ch. 17 - Consider the following reaction at 298 K:...Ch. 17 - As an approximation, we can assume that proteins...Ch. 17 - Which of the following are not state functions: S,...Ch. 17 - Which of the following is not accompanied by an...Ch. 17 - Hydrogenation reactions (for example, the process...Ch. 17 - Give a detailed example of each of the following,...Ch. 17 - At 0 K, the entropy of carbon monoxide crystal is...Ch. 17 - Comment on the correctness of the analogy...Ch. 17 - The standard enthalpy of formation and the...Ch. 17 - In chemistry, the standard state for as solution...Ch. 17 - The following diagram shows the variation of the...Ch. 17 - Consider the gas-phase reaction between A2 (green)...Ch. 17 - The KP for the reaction N2+3H22NH3 is 2.4 103 at...Ch. 17 - The table shown here lists the ion-product...Ch. 17 - Draw the missing distributions in Figure 17.2....Ch. 17 - The reaction NH3(g)+HCl(g)NH4Cl(s) is spontaneous...Ch. 17 - The boiling point of diethyl ether is 34.6C....Ch. 17 - Nicotine is the compound in tobacco responsible...Ch. 17 - Estimate S for the process depicted in Figure...Ch. 17 - At what point in the series HOnH(g) (n = 1, 2, 3,...
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