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Find Δ³Ò∘ for the reactions in Problem 20.50 using Δ±áf∘ and S∘ values.

Short Answer

Expert verified

Reaction-A the value of standard free energy isΔ³Òrxno=-1138kJ¯.

Reaction-B the value of standard free energy is Δ³Òrxno=-1379kJ¯.

Reaction-C the value of standard free energy is Δ³Òrxno=-226kJ¯.

Step by step solution

01

Concept.

Solubility: The maximum amount of solute that can be dissolved in the solvent at equilibrium is defined as solubility.

Constant of soluble product: For equilibrium between solids and their respective ions in a solution, the solubility product constant is defined. In general, the term "solubility product" refers to water-equilibrium insoluble or slightly soluble ionic substances.

02

 Find ΔG∘ for the reactions-A

Reaction-A

Considering the given Chemical reaction:

BaO(s)+CO2(g)→BaCO3(s)

The number of particles decreases as well, indicating that entropy is decreasing.

As a result, the localid="1663373089546" Δ³Òfovalues are zero, indicating that the solid is less than the gas.

Standard enthalpy change is,

The reaction's enthalpy change is calculated as follows:

localid="1663373436489" Δ±árxno=∑mΔ±áf(Products)o-∑nΔ±áf(reactants)oΔ±árxno=(1molMgO)Δ±áfoofMgO-(2molMg)Δ±áfoofMg+1molO2Δ±áfoofO2=[(2molMgO)(-601.2kJ/mol)]-(2molMg)(0kJ/mol)+(1molO)2(0kJ/mol)Δ±árxno=-1202.4kJ

The enthalpy change is negative. Hence, the enthalpy Δ±árxnovalue is -1202.4kJ

Entropy change Δ³§systemo

The standard equation for entropy change is:

Δ³§rxno=∑mSProductso-∑nSreactantso

Where, (m) and (n) are the stoichiometric co-efficient.

Δ³§rxno=(1molMgO)SoofMgg-(2molMg)SoofMg+1molO2SoofO2Δ³§rxno=[(1molMgO)(26.9J/mol×K)]-2molN2(32.69J/mol×K)+1mol2(205.0J/mol×K)

Therefore, the Δ³§rxn0of the reaction is -216.58J/K

Calculate the change in free energy Δ³Òrxnonext.

Standard Free energy change equation is,

Δ³Òrxno=Δ±árxno-TΔ³§rxno

Free energy changeΔ³Òfo

The enthalpy and entropy values calculated are

Δ±árxno=-1202.4kJΔ³§rxno=-216.58J/K

These figures are used to fill in the blanks in the standard free energy equation.

Δ³Òrxno=-1202.4kJ-(298K)(-216.58J/K)1kJ/103JΔ³Òrxno=-1137.859kJ

Therefore, the standard free energy value is localid="1663373970893" Δ³Òrxno=-1138kJ.

03

Find ΔG∘for the reactions-B.

Reaction-B

Considering the given Chemical reaction:

2CH3OH(g)+3O2(g)→2CO2(g)+4H2O(g)

The number of particles decreases as well, indicating that entropy is decreasing.

As a result, the values are zero, indicating that the solid is less than the gas.

The standard enthalpy change formula is:

The reaction's enthalpy change is calculated as follows:

Δ±árxno=∑mΔ±áf(Products)o-∑nΔ±áf(reactants)oΔ±árxno=2molCO2Δ±árxnoofCO2+4molH2OΔ±árxnoofH2O-2molCH3OHΔ±árxnoofCH3OH+3molO2Δ±árxnoofO2]Δ±árxno=2molCO2(-393.5kJ/mol)+(4molH2O)(-241.826kJ/mol)2molCHH3OH(-201.2kJ/mol)+3molO2(0kJ/mol)Δ±árxno=-1351.904kJ

The change in enthalpy is negative.

Hence, the enthalpy Δ±árxno value is -1351.904kJ

Entropy changeΔ³§systemo.

Standard entropy change equation is,

Where, (m) and (n) are the stoichiometric co-efficient.

Δ³§rxno=2molCO2SoofCO2+4molH2OSoofH2O-2molCH3OHSoofCH3OH+3molO2SoofO2Δ³§rxno=2molCO2(213.7J/mol×K)+4molHH2O(188.72J/mol×K)2molCH3OH(238J/mol×K)+3molO2(205.0J/mol×K)Δ³§rxno=-91.28J/K

Therefore, the Δ³§rxn0of the reaction is -91.28J/K

Next calculate the Free energy change Δ³Òrxno

standard Free energy change equation is,

Δ³Òrxno=Δ±árxno-TΔ³§rxno

Free energy change Δ³Òfo

The values of calculated enthalpy and entropy are,

Δ±árxno=-1351.904kJΔ³§rxno=-91.28J/K

These figures are used to fill in the blanks in the standard free energy equation.

Δ³Òrxno=-1351.904kJ-(298K)(-91.28J/K)1kJ/103JΔ³Òrxno=-1379.105kJ

Therefore, the standard free energy value is Δ³Òrxno=-1379kJ¯.

04

 Find ΔG∘for the reactions-C.

Reaction-C

Considering the given Chemical reaction:

BaO(s)+CO2(g)→BaCO3(s)

The number of particles decreases as well, indicating that entropy is decreasing.

As a result, the Δ³Òfovalues are zero, indicating that the solid is less than the gas.

The standard enthalpy change formula is:

The reaction's enthalpy change is calculated as follows:

localid="1663375260779" Δ±árxno=∑mΔ±áf(Products)o-∑nrΔ±áf(reactants)oΔ±árxno=1molBaCOB3Δ±árxnoofBaCO3-(1molBaO)Δ±árxnoofBaO+1molCOCO2Δ±árxnoofCO2=[(1molBaCO3)(-1219kJ/mol)]-[(1molBaO)(-548.1kJ/mol)+1molCO2(-393.5kJ/mol)Δ±árxno=-277.4kJ

The enthalpy change is negative. Hence, the enthalpy Δ±árxno value is -277.4kJ

Entropy change Δ³§systemo

Standard entropy change equation is,

Where, (m) and (n) are the stoichiometric co-efficient.

localid="1663375451404" Δ³§rxno=2molBaCO3SoofBaCO3-(1molBaO)SoofBaO+(1molCO2)SoofCO2=[(1mol)(112J/mol×K)]-[(1mol)(72.07J/mol×K)+(1mol)(213.7J/mol×K)]Δ³§rxno=-173.77J/K

Therefore, the Δ³§rxnoof the reaction is -173.77J/K

Finally calculate the Free energy change Δ³Òrxno

Standard Free energy change equation is,

Δ³Òrxno=Δ±árxno-TΔ³§rxno

Free energy change Δ³Òfo

Calculated enthalpy and entropy values are

DHrxno=-277.4kJDSrxno=-173.77J/K

These values are plugging above standard free energy equation,

Δ³Òrxno=-277.4kJ-(298K)(-173.77J/K)1kJ/103JΔ³Òrxno=-225.6265kJ

Therefore, the standard free energy value is Δ³Òrxno=-225.6265kJ.

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