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Chemistry & Chemical Reactivity

9th Edition
John C. Kotz + 3 others
Publisher: Cengage Learning
ISBN: 9781133949640

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Section
BuyFindarrow_forward

Chemistry & Chemical Reactivity

9th Edition
John C. Kotz + 3 others
Publisher: Cengage Learning
ISBN: 9781133949640
Chapter 18, Problem 8PS
Textbook Problem
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Calculate the standard entropy change for the following reactions at 25 °C. Comment on the sign of ΔrS°.

(a) 2 Na(s) + 2 H2O() → 2 NaOH(aq) + H2(g)

(b) Na2CO3(s) + 2 HCl(aq) → 2 NaCl(aq) + H2O() + CO2(g)

(a)

Interpretation Introduction

Interpretation:

The standard entropy changes for reaction 2Na(s)+2H2O(l)2NaOH(aq)+H2(g) should be calculated.

Concept Introduction:

Entropy is a measure of the randomness of the system. It is a thermodynamic quantity and an extensive property. It is represented by the symbol S. It can also be defined as the degree of energy dispersal. More the dispersal in energy, more is the value if entropy.

The standard entropy change for any reaction is the sum of standard molar entropies of product, subtracted from the sum of standard molar entropies of reactants. The standard molar entropies are multiplied by the stoichiometric coefficient which is as per the balanced equation.

  ΔrS°=nS°(products)nS°(reactants)

Explanation of Solution

The standard entropy change for the reaction of sodium with water is calculated below.

Given: 2Na(s)+2H2O(l)2NaOH(aq)+H2(g)

The standard entropy of NaOH(aq) is 48.1 J/Kmol

The standard entropy of Na(s) is 51.21 J/Kmol

The standard entropy of H2(g) is 130.7 J/Kmol

The standard entropy of H2O(l) is 69.95 J/Kmol

The balanced chemical equation for the reaction of sodium with water is 2Na(s)+2H2O(l)2NaOH(aq)+H2(g)

The expression for the standard entropy change is,

  ΔrS°=nS°(products)nS°(reactants)=[[(2 mol NaOH(aq)/mol-rxn)S°[NaOH(aq)]+(1 mol H2(g)/mol-rxn)S°

(b)

Interpretation Introduction

Interpretation:

The standard entropy changes for reaction Na2CO3(s)+2HCl(aq)2NaCl(aq)+H2O(l)+CO2(g) should be calculated.

Concept Introduction:

Entropy is a measure of the randomness of the system. It is a thermodynamic quantity and an extensive property. It is represented by the symbol S. It can also be defined as the degree of energy dispersal. More the dispersal in energy, more is the value if entropy.

The standard entropy change for any reaction is the sum of standard molar entropies of product, subtracted from the sum of standard molar entropies of reactants. The standard molar entropies are multiplied by the stoichiometric coefficient which is as per the balanced equation.

  ΔrS°=nS°(products)nS°(reactants)

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Chapter 18 Solutions

Chemistry & Chemical Reactivity
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Ch. 18.4 - Without looking up their standard entropies in...Ch. 18.4 - Without doing any calculations, predict the sign...Ch. 18.4 - Calculate rS for the following reaction at 25 C....Ch. 18.5 - Based on rH and rS, predict the spontaneity of the...Ch. 18.5 - Calculate rS for the following reaction at 25 C...Ch. 18.5 - Calculate S(universe) for the following reaction...Ch. 18.5 - 3. If rH° = +467.9 kJ/mol-rxn and rS° = +560.7 J/K...Ch. 18.6 - For a reaction to be spontaneous, rG will be...Ch. 18.6 - A reaction for which rG 0 is (a) product-favored...Ch. 18.7 - Using values of fH and S to find rH and rS,...Ch. 18.7 - Calculate the standard free energy change for the...Ch. 18.7 - Oxygen was first prepared by Joseph Priestley...Ch. 18.7 - Determine the value of rG for the reaction C(s) +...Ch. 18.7 - Determine the value of the equilibrium constant,...Ch. 18.7 - Nitrogen and oxygen can react to form nitrogen...Ch. 18.7 - 1. Given that H° = −2219 kJ/mol-rxn and that rS° =...Ch. 18.7 - 2. Using values of rG°, determine the value of rG°...Ch. 18.7 - 3. The value of Kp for the following reaction at...Ch. 18.7 - Consider the hydrolysis reactions of creatine...Ch. 18.7 - Assume the reaction A(aq) + B(aq) C(aq) +...Ch. 18.A - The decomposition of diamond to graphite...Ch. 18.A - It has been demonstrated that buckminsterfullerene...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 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 - 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 - Write a balanced equation that depicts the...Ch. 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 - The following reaction is reactant-favored at...Ch. 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 - Estimate the vapor pressure of ethanol at 37 C...Ch. 18 - The equilibrium constant, Kp, for N2O4(g) 2...Ch. 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 - 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