Concept explainers
Set up a Hess’s law cycle, and use the following information to calculate ΔH°f for aqueous nitric acid, HNO3(aq). You will need to use fractional coefficients for some equations.
Want to see the full answer?
Check out a sample textbook solutionChapter 8 Solutions
General Chemistry: Atoms First
- The process of dissolving ammonium nitrate, NH4NO3, in water is an endothermic process. What is the sign of q? If you were to add some ammonium nitrate to water in a flask, would you expect the flask to feel warm or cool?arrow_forwardThe head of a strike anywhere match contains tetraphosphorus trisulfide, P4S3. In an experiment, a student burned this compound in an excess of oxygen and found that it evolved 3651 kJ of heat per mole of P4S3 at a constant pressure of 1 atm. She wrote the following thermochemical equation: P4S3(s)+8O2(g)P4O10(s)+3SO2(g);H=3651kJ Calculate the standard enthalpy of formation of P4S3, using this students result and the following standard enthalpies of formation: P4O10(s), 3009.9 kJ/mol; SO2(g), 296.8 kJ/mol. How does this value compare with the value given in Appendix C?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_forward
- Hydrogen sulfide, H2S, is a poisonous gas with the odor of rotten eggs. The reaction for the formation of H2S from the elements is H2(g)+18S3(rhombic)H2S(g) Use Hesss law to obtain the enthalpy change for this reaction from the following enthalpy changes: H2S(g)+32O2(g)H2O(g)+SO2(g);H=518kJH2(g)+12O2(g)H2O(g);H=242kJ18S8(rhombic)+O2(g)SO2(g);H=297kJarrow_forwardThe decomposition of ozone, O3, to oxygen, O2, is an exothermic reaction. What is the sign of q? If you were to touch a flask in which ozone is decomposing to oxygen, would you expect the flask to feel warm or cool?arrow_forwardEthylene glycol, HOCH2CH2OH, is used as antifreeze. It is produced from ethylene oxide, C2H4O, by the reaction C2H4O(g)+H2O(l)HOCH2CH2OH(l) Use Hesss law to obtain the enthalpy change for this reaction from the following enthalpy changes: 2C2H4O(g)+5O2(g)4CO2(g)+4H2O(l);H=2612.2kJHOCH2CH2OH(l)+52O2(g)2CO2(g)+3H2O(l);H=1189.8kJarrow_forward
- Nitrogen gas (2.75 L) is confined in a cylinder under constant atmospheric pressure (1.01 105 pascals). The volume of gas decreases to 2.10 L when 485 J of energy is transferred as heat to the surroundings. What is the change in internal energy of the gas?arrow_forwardWhen solid iron burns in oxygen gas (at constant pressure) to produce Fe2O3(s), 1651 kJ of heat is released for every 4 mol of iron burned. How much heat is released when 10.3 g Fe2O3(s) is produced (at constant pressure)? What additional information would you need to calculate the heat released to produce this much Fe2O3(s) if you burned iron in ozone gas, O3(g), instead of O2(g)?arrow_forwardThe specific heat capacity of copper is 0.385 J g1 C1, whereas it is 0.128 J g1 C1 for gold. Assume you place 100. g of each metal, originally at 25 C, in a boiling water bath at 100 C. If energy is transferred to each metal at the same rate, determine which piece of metal will reach 100 C first.arrow_forward
- A 250-g sample of water at 20.0C is placed in a freezer that is held at a constant temperature of 20.0C. Considering the water as the system, answer the following questions: a What is the sign of qsys for the water after it is placed in the freezer? b After a few hours, what will be the state of the water? c How will the initial enthalpy for the water compare with the final enthalpy of the water after it has spent several hours in the freezer? d What will the temperature of the water be after several hours in the freezer?arrow_forward9.42 Why is enthalpy generally more useful than internal energy in the thermodynamics of real world systems?arrow_forwardThe standard molar enthalpy of formation of diborane, B2H6(g), cannot be determined directly because the compound cannot be prepared by the reaction of boron and hydrogen. It can be calculated from other enthalpy changes, however. The following enthalpy changes can be measured. 4 B(s) + 3 O2(g) 2 B2O3(s) rH = 2543.8 kJ/mol-rxn H2(g) + O2(g) H2O(g) rH = 241.8 kl/mol-rxn B2H6(g) + 3 O2(g) B2O3(s) + 3 H2O(g) rH = 2032.9 kJ/mol-rxn (a) Show how these equations can be added together to give the equation for the formation of B2H6(g) from B(s) and H2(g) in their standard states. Assign enthalpy changes to each reaction. (b) Calculate fH for B2H6(g). (c) Draw an energy level diagram that shows how the various enthalpies in this problem are related. (d) Is the formation of B2H6(g) from its elements exo- or endothermic?arrow_forward
- Chemistry: The Molecular ScienceChemistryISBN:9781285199047Author:John W. Moore, Conrad L. StanitskiPublisher:Cengage LearningChemistry: Principles and PracticeChemistryISBN:9780534420123Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward MercerPublisher:Cengage LearningGeneral Chemistry - Standalone book (MindTap Cour...ChemistryISBN:9781305580343Author:Steven D. Gammon, Ebbing, Darrell Ebbing, Steven D., Darrell; Gammon, Darrell Ebbing; Steven D. Gammon, Darrell D.; Gammon, Ebbing; Steven D. Gammon; DarrellPublisher:Cengage Learning
- Chemistry for Engineering StudentsChemistryISBN:9781337398909Author:Lawrence S. Brown, Tom HolmePublisher:Cengage LearningChemistry by OpenStax (2015-05-04)ChemistryISBN:9781938168390Author:Klaus Theopold, Richard H Langley, Paul Flowers, William R. Robinson, Mark BlaserPublisher:OpenStaxChemistry: Principles and ReactionsChemistryISBN:9781305079373Author:William L. Masterton, Cecile N. HurleyPublisher:Cengage Learning