Ch. 17 - Chemical ThermodynamicsSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: The process by which plants convert CO2 and H2O into C6H12O6 and O2 is called photosynthesis. This process is nonspontaneous, so energy must be provided to make the reaction occur, and that energy is provided by sunlight. “Chemosynthesis” refers to the biological conversion of simple carbon-containing molecules (e.g. CO2 or methane, CH4) into more complex energy-rich molecules using non-biological (inorganic) molecules as the energy source, rather than sunlight, as in photosynthesis. For example, giant tube worms found near deep-ocean sulfur vents contain bacteria that convert carbon dioxide to simple sugars using hydrogen sulfide as the energy source according to the chemical equation 12H2S + 6CO2 → C6H12O6 + 6H2O + 12S  A. Using the data provided below, calculate the following thermodynamic parameters for the above reaction.  1. ΔH°    2. ΔS°    3. ΔG°   B. Note the value you calculated for ΔG°. The normal expectation is that the reaction is spontaneous, but the calculations indicate that the reaction is nonspontaneous at 25°C.  At what temperature will the reaction become spontaneous?  When the reaction becomes spontaneous, will it be driven by enthalpy or entropy? 

Problem

The process by which plants convert CO2 and H2O into C6H12O6 and O2 is called photosynthesis. This process is nonspontaneous, so energy must be provided to make the reaction occur, and that energy is provided by sunlight. “Chemosynthesis” refers to the biological conversion of simple carbon-containing molecules (e.g. CO2 or methane, CH4) into more complex energy-rich molecules using non-biological (inorganic) molecules as the energy source, rather than sunlight, as in photosynthesis. For example, giant tube worms found near deep-ocean sulfur vents contain bacteria that convert carbon dioxide to simple sugars using hydrogen sulfide as the energy source according to the chemical equation

12H2S + 6CO2 → C6H12O6 + 6H2O + 12S 

A. Using the data provided below, calculate the following thermodynamic parameters for the above reaction. 

1. ΔH° 

 

2. ΔS° 

 

3. ΔG°

 

B. Note the value you calculated for ΔG°. The normal expectation is that the reaction is spontaneous, but the calculations indicate that the reaction is nonspontaneous at 25°C. 

At what temperature will the reaction become spontaneous? 

When the reaction becomes spontaneous, will it be driven by enthalpy or entropy?