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.
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?