Use the information in the table to calculate delta H in kilojoules fr phosynthe

Question

Use the information in the table to calculate delta H in kilojoules fr phosynthesis of glucose Use the information in the table to calculate delta Hdegree in kilojoules for the photosynthesis of glucose (C6H12O6) and O2 from CO2 and liquid H2O. a reaction carried out by all green plants. TABLE Standard Heats of Formation for Some Common Substances at 25 degree C Express your answer using four significant figures. To understand how standard enthalpy of reaction is related to the standard heats of formation of the reactants and products The standard enthalpy of reaction is the enthalpy change that occurs in a reaction when all the reactants and products are in their standard states The symbol for the standard enthalpy of reaction is delta Hrxn degree where the subscript "rxn" stands for "reaction" The standard enthalpy of a reaction is calculated from the standard heats of formation ( delta Hf degree) (subscript "f" for formation) of its reactants and products Therefore, the standard enthalpy delta Hrxn degree of any reaction can be mathematically determined, as long as the standard heats of formation (delta Hr degree) of its reactants and products are known. In a generic chemical reaction involving reactants A and B and products C and D. aA + bB rightarrow cC + dD. the standard enthalpy delta Hrxn degree of the reaction is given by Notice that the stoichiometric coefficients, a. b. c. d. are an important part of this equation This formula is often generalized as follows, where the first sum on the right-hand side of the equation is a sum over the products and the second sum is over the reactants where m and n represent the appropriate stoichiometric coefficients for each substance What is delta Hrxn degree for the following chemical reaction? CS2(g) + 2H2O(l) rightarrow CO2(g) + 2H2S(g) You can use the following table of standard heats of formation to calculate the enthalpy of the given reaction Express the standard enthalpy of reaction to three significant figures and include the appropriate units.

Explanation / Answer

The overall chemical reaction involved in photosynthesis is: 6CO2 + 6H2O (+ light energy) C6H12O6 + 6O2 Given: ?Hf of CO2 = -393.5 kJ/mol ?Hºf of H2O = -285.8 kJ/mol ?Hºf of O2 = 0 kJ/mol [Since O2 is in elemental state] ?Hºf of C6H12O6 = -1273.3 kJ/mol ? ?H for the photosynthesis reaction is given by: ?Hº = ??vp?Hºf(products) - ?? vr?Hºf(reactants) Where: vp= stoichiometric coefficient of the product vr= stoichiometric coefficient of the reactants ?Hºf= standard enthalpy of formation for the reactants or the products ? ?Hºr = -1273.3 - [(6*-393.5) + (6* -285.8)] = 2802.5 kJ/mol Rounded to 4 significant figures it is 2802 kJ/mol.

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