Living organisms use energy from the metabolism of food to create an energy-rich molecule called adenosine triphosphate (ATP). The ATP acts as an energy source for a variety of reactions that the living organism must carry out to survive. ATP provides energy through its hydrolysis, which can be symbolized as follows: ATP(aq) + H2O(l) → ADP(aq) + Pi(aq) ΔG°rxn = -30.5 kJ where ADP represents adenosine diphosphate and Pi represents an inorganic phosphate group (such as HPO42-). b. The free energy obtained from the oxidation (reaction with oxygen) of glucose (C6H12O6) to form carbon dioxide and water can be used to re-form ATP by driving the given reaction in reverse. Calculate the standard free energy change for the oxidation of glucose and estimate the maximum number of moles of ATP that can be formed by the oxidation of one mole of glucose.
Ch.18 - Free Energy and Thermodynamics
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831
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TOC.tableOfContents
- Ch.1 - Matter, Measurement & Problem Solving136
- Ch.2 - Atoms & Elements112
- Ch.3 - Molecules, Compounds & Chemical Equations159
- Ch.4 - Chemical Quantities & Aqueous Reactions140
- Ch.5 - Gases118
- Ch.6 - Thermochemistry106
- Ch.7 - Quantum-Mechanical Model of the Atom62
- Ch.8 - Periodic Properties of the Elements103
- Ch.9 - Chemical Bonding I: The Lewis Model104
- Ch.10 - Chemical Bonding II: Molecular Shapes & Valence Bond Theory89
- Ch.11 - Liquids, Solids & Intermolecular Forces73
- Ch.12 - Solids and Modern Material59
- Ch.13 - Solutions110
- Ch.14 - Chemical Kinetics140
- Ch.15 - Chemical Equilibrium78
- Ch.16 - Acids and Bases155
- Ch.17 - Aqueous Ionic Equilibrium176
- Ch.18 - Free Energy and Thermodynamics108
- Ch.19 - Electrochemistry118
- Ch.20 - Radioactivity and Nuclear Chemistry82
- Ch.21 - Organic Chemistry150
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Non è quello che usi tu?Cambia libro di testo
Capitolo 18, Problema 94
Calculate ΔG° at 298 K for these reactions and predict the effect on ΔG° of lowering the temperature.
a. NH3(g) + HBr(g) → NH4Br(s)
b. CaCO3(s) → CaO(s) + CO2(g)
c. CH4(g) + 3 Cl2(g) → CHCl3(g) + 3 HCl(g) (ΔG°f for CHCl3(g) is -70.4 kJ/mol.)
Guida verificata passo dopo passo1
Identify the reaction: CaCO_3(s) \(\rightarrow\) CaO(s) + CO_2(g).
Use the standard Gibbs free energy change formula: \( \Delta G^\circ = \Delta H^\circ - T\Delta S^\circ \).
Look up the standard enthalpy change (\( \Delta H^\circ \)) and standard entropy change (\( \Delta S^\circ \)) for each substance involved in the reaction from a data table.
Calculate \( \Delta H^\circ \) and \( \Delta S^\circ \) for the reaction using the formula: \( \Delta X^\circ = \sum \Delta X^\circ_{\text{products}} - \sum \Delta X^\circ_{\text{reactants}} \), where \( X \) is either enthalpy or entropy.
Substitute the values of \( \Delta H^\circ \), \( \Delta S^\circ \), and \( T = 298 \text{ K} \) into the Gibbs free energy formula to find \( \Delta G^\circ \). Consider the effect of lowering the temperature on \( \Delta G^\circ \) by analyzing the term \( -T\Delta S^\circ \).
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Concetti chiave
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Gibbs Free Energy (ΔG)
Gibbs Free Energy (ΔG) is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure. It is a crucial concept in predicting the spontaneity of a reaction; a negative ΔG indicates a spontaneous process, while a positive ΔG suggests non-spontaneity. The standard Gibbs free energy change (ΔG°) is calculated under standard conditions, providing a reference point for reactions.
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01:51
Gibbs Free Energy of Reactions
Temperature's Effect on ΔG
The temperature of a system can significantly influence the Gibbs free energy change (ΔG) of a reaction. According to the Gibbs-Helmholtz equation, ΔG is dependent on both enthalpy (ΔH) and entropy (ΔS) changes of the reaction. Lowering the temperature generally decreases the contribution of the entropy term (TΔS) to ΔG, which can lead to an increase in ΔG for reactions that are entropy-driven, potentially shifting the reaction from spontaneous to non-spontaneous.
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02:31Photoelectric Effect
Reaction Quotient (Q) and Equilibrium
The reaction quotient (Q) is a measure of the relative amounts of products and reactants present in a reaction at any point in time, compared to their equilibrium concentrations. It helps in determining the direction in which a reaction will proceed to reach equilibrium. For the reaction CaCO3(s) → CaO(s) + CO2(g), understanding Q is essential for predicting how changes in temperature and concentration will affect the spontaneity and equilibrium position of the reaction.
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00:49Reaction Quotient Q
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These reactions are important in catalytic converters in automobiles. Calculate ΔG° for each at 298 K. Predict the effect of increasing temperature on the magnitude of ΔG°.
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