Concept explainers
Combustion reactions involve reacting a substance with oxygen. When compounds containing carbon and hydrogen are combusted, carbon dioxide and water are the products. Using the enthalpies of combustion for
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Chemical Principles
- At 298 K, the standard enthalpies of formation for C2H2(g) and C6H6(l) are 227 kJ/mol and 49 kJ/mol, respectively. a. Calculate H for C6H6(l)3C2H2(g) b. Both acetylene (C2H2) and benzene (C6H6) can be used as fuels. Which compound would liberate more energy per gram when combusted in air?arrow_forwardGasohol, a mixture of gasoline and ethanol, C2H5OH, is used as automobile fuel. The alcohol releases energy in a combustion reaction with O2. C2H5OH(l)+3O2(g)2CO2(g)+3H2O(l) If 0.115 g ethanol evolves 3.62 kJ when burned at constant pressure, calculate the combustion enthalpy for ethanol.arrow_forwardUse Appendix L to find the standard enthalpies of formation of oxygen atoms, oxygen molecules (O2), and ozone (O3). What is the standard state of oxygen? Is the formation of oxygen atoms from O2 exothermic? What is the enthalpy change for the formation of 1 mol of O3 from O2?arrow_forward
- When a gas expands, what is the sign of w? Why? When a gas contracts, what is the sign of w? Why? What are the signs of q and w for the process of boiling water?arrow_forward9.42 Why is enthalpy generally more useful than internal energy in the thermodynamics of real world systems?arrow_forwardUnder what circumstances is the heat of a process equal to the enthalpy change for the process?arrow_forward
- The enthalpy of combustion of solid carbon to form carbon dioxide is 393.7 KJ/mol carbon, and the enthalpy of combustion of carbon monoxide to form carbon dioxide is 283.3 KJ/mol CO. Use these data to calculate H for the reaction 2C(s)+O2(g)2CO(g)arrow_forwardHow is the sign of q, heat, defined? How does it relate to the total energy of the system?arrow_forward
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