The following data compare the standard enthalpies and free energies of formation of some crystalline ionic substances and aqueous solutions of the substances:
Substance | ΔHOf (KJ / mol) | Δ GOf (KJ / mol) |
AgNO3(s) | −124.4 | −33.4 |
AgNO3(aq) | −101.7 | −34.2 |
MgSO4(S) | −1283.7 | -1169.6 |
MgSO4(aq) | −1374.8 | -1198.4 |
Write the formation reaction for AgNO3 (s). Based on this reaction, do you expect the entropy of the system to increase or decrease upon the formation of AgNO3 (s)?
(b) Use ΔHO f and ΔGO f of AgNO3 (S) to determine the entropy change upon formation of the substance. Is your answer consistent with your reasoning in part (a)?
(c ) Is dissolving AgNO3 in water an exothermic or endothermic process?
What about dissolving MgSO4 in water?
(d) For both AgNO3 and MgSO4, use the data to calculate the entropy change when the solid is dissolved in water.
(e) Discuss the results from part (d) with reference to material presented in this chapter and in the “A Closer Look” box on page 814.
Want to see the full answer?
Check out a sample textbook solutionChapter 5 Solutions
Chemistry: The Central Science (13th Edition)
- Give the definition of the standard enthalpy of formation for a substance. Write separate reactions for the formation of NaCl, H2O , C6H12O6, and PbSO4 that have H values equal to Hf for each compound.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_forwardWhite phosphorus, P4, ignites in air to produce P4O10. When 3.56 g P4 is burned, 85.8 kJ of thermal energy is evolved at constant pressure. Calculate the combustion enthalpy of P4.arrow_forward
- Given: 2Cu2O(s) + O2(g) 4CuO(s)H = 288 kJ Cu2O(s) CuO(s) + CuO(s)H = 11kJ Calculate the standard enthalpy of formation (Ht) for CuO(s).arrow_forward9.42 Why is enthalpy generally more useful than internal energy in the thermodynamics of real world systems?arrow_forwardThe 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_forward
- The 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_forwardThe formation of aluminum oxide from its elements is highly exothermic. If 2.70 g Al metal is burned in pure O2 to give A12O3, calculate how much thermal energy is evolved in the process (at constant pressure).arrow_forwardUnder what circumstances is the heat of a process equal to the enthalpy change for the process?arrow_forward
- Chemistry: The Molecular ScienceChemistryISBN:9781285199047Author:John W. Moore, Conrad L. StanitskiPublisher:Cengage LearningChemistry & Chemical ReactivityChemistryISBN:9781337399074Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage LearningChemistry & Chemical ReactivityChemistryISBN:9781133949640Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage Learning
- Chemistry: An Atoms First ApproachChemistryISBN:9781305079243Author:Steven S. Zumdahl, Susan A. ZumdahlPublisher:Cengage LearningChemistryChemistryISBN:9781305957404Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCostePublisher:Cengage Learning