dard enthalpy 6.68 (a) What is the value of the standard enthalpy of formation of an element in its most stable form? (b) Write the chemi. cal equation for the reaction whose enthalpy change is the standard enthalpy of formation of sucrose (table sugar), enthalpy of formation? C12H2„O11($), AHf°[C12H22O11(S)]. 6.69 For each of the following compounds, write a balanced ther. mochemical equation depicting the formation of one mole of the compound from its elements in their standard states and then look up AH°r for each substance in Appendix C. (a) NO2(8), (b) SO3(8), (c) NaBr(s), (d) Pb(NO3)2(s). 6.70 Write balanced equations that describe the formation of the following compounds from elements in their standard states, and then look up the standard enthalpy of formation for each substance in Appendix C: (a) H2O2(8), (b) CaCO3(s). (c) POCI3(1), (d) C,H;OH(1). 6.71 The following is known as the thermite reaction:ods 2 Al(s) + Fe2O3(s) Al203(s) + 2 Fe(s) This highly exothermic reaction is used for welding massive units, such as propellers for large ships. Using standard en- thalpies of formation in Appendix C, calculate AH° for this reaction. CH'OH

dard enthalpy 6.68 (a) What is the value of the standard enthalpy of formation of an element in its most stable form? (b) Write the chemi. cal equation for the reaction whose enthalpy change is the standard enthalpy of formation of sucrose (table sugar), enthalpy of formation? C12H2„O11($), AHf°[C12H22O11(S)]. 6.69 For each of the following compounds, write a balanced ther. mochemical equation depicting the formation of one mole of the compound from its elements in their standard states and then look up AH°r for each substance in Appendix C. (a) NO2(8), (b) SO3(8), (c) NaBr(s), (d) Pb(NO3)2(s). 6.70 Write balanced equations that describe the formation of the following compounds from elements in their standard states, and then look up the standard enthalpy of formation for each substance in Appendix C: (a) H2O2(8), (b) CaCO3(s). (c) POCI3(1), (d) C,H;OH(1). 6.71 The following is known as the thermite reaction:ods 2 Al(s) + Fe2O3(s) Al203(s) + 2 Fe(s) This highly exothermic reaction is used for welding massive units, such as propellers for large ships. Using standard en- thalpies of formation in Appendix C, calculate AH° for this reaction. CH'OH

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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Consider the following reaction. CH3OH(g) CO(g) + 2 H2(g) H = +90.7 kJ (a) Is the reaction exothermic or endothermic? endothermicexothermic (b) Calculate the amount of heat transferred when 40.0 g of CH3OH(g) are decomposed by this reaction at constant pressure.H = kJ(c) If the enthalpy change is 11.0 kJ, how many grams of hydrogen gas are produced? g(d) How many kilojoules of heat are released when 13.5 g of CO(g) reacts completely with H2(g) to form CH3OH(g) at constant pressure?H = kJ(e) Calculate E when 360.0 g of CH3OH(g) completely reacts at a constant temperature of 300 K and constant pressure of 0.95 atm. R = 8.314 J/mol*K and R = 0.08206 atm*L/mol*K kJ HopHelpCh5N1
and 2 Enthalpy #1.30 enoindice pled TT 2010 2D49.bs 22) When 1 mole of Fe2O3(s) reacts with H₂(g) to form Fe(s) and H2O(g) according to the following equation, 98.8 kJ of energy are absorbed. (6 Fe2O3(s) + 3 H2(g) → 2 Fe(s) + 3 H₂O(g) (pp) (20/d4 (pm) $40 D Reaclanis 13:48 SH Products endothermic, A endothermic, B (2) exothermic, A exothermic, B nad W (21 Enthalpy MOMS. Reactants Products (A) (B) Is the reaction endothermic or exothermic, and which of the enthalpy diagrams above represents grow olor and to noin (01 this reaction? SH GH TH A HOMH X HILD 08.10 Page 6 of 8
O THERMOCHEMISTRY Using Hess's Law to calculate net reaction enthalpy Lindsay Dimethyl ether, a useful organic solvent, is prepared in two steps. In the first step, carbon dioxide and hydrogen react to form methanol and water: CO,(g) + 3 H,(g) → CH;OH(1) + H,0(1) AH=-131. kJ In the second step, methanol reacts to form dimethyl ether and water: 2 CH,OH(1) → CH;OCH,(g) + H,0(1) AH=8. kJ Calculate the net change in enthalpy for the formation of one mole of dimethyl ether from carbon dioxide and hydrogen from these reactions. Round your answer to the nearest kJ. II
Sulfur dioxide, SO2(g), can react with oxygen to produce sulfur trioxide, SO3(g), by the reaction 2 SO2(g) + O2(g) → 2 SO3(g) The standard enthalpies of formation for SO2(g) and SO3(g) are AH; [SO2(g)] = -296.8 kJ/mol AH; [SO3(g)] = -395.7 kJ/mol Calculate the amount of energy in the form of heat that is produced when a volume of 2.25 L of SO2(g) is converted to 2.25 L gas behavior. of SO3(g) according to this process at a constant pressure and temperature of 1.00 bar and 25.0 °C. Assume ideal AH= kJ
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5.67 (a) What is meant by the term standard conditions with zec erence to enthalpy changes? (b) What is meant by the ferm enthalpy of formation? (c) What is meant by the term standard enthalpy of formation? os gniwollol ori 19bian T0
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When methanol, CH3OH,CH3OH, is burned in the presence of oxygen gas, O2,O2, a large amount of heat energy is released. For this reason, it is often used as a fuel in high performance racing cars. The combustion of methanol has the balanced, thermochemical equation CH3OH(g)+32O2(g)⟶CO2(g)+2H2O(l)ΔH=−764 kJCH3OH(g)+32O2(g)⟶CO2(g)+2H2O(l)ΔH=−764 kJ How much methanol, in grams, must be burned to produce 639 kJ639 kJ of heat?
（1）Consider the reaction: 2A (g) + 3 B (g) → 2 C (g) ΔHrxn = +254.3 kJ What will be the enthalpy change (in kJ) if 0.471 mol B reacts in excess A? （2）Consider the reaction: C (s) + O2 (g) → CO2 (g) ΔHrxn = -393.5 kJ What mass of carbon (in g) must be reacted via this mechanism to release 581.2 kJ of heat?
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6.116 Ethylene glycol, HOCH,CH;OH, is used as anti- freeze. It is produced from ethylene oxide, C,H,O, by the reaction C,H,0(g) + H,0(1) — НОСН,СH,0Н() Use Hess's law to obtain the enthalpy change for this reac- tion from the following enthalpy changes: 2C,H,0(g) + 5O2(g)· → 4CO2(g) + 4H,O(l); AH = -2612.2 kJ НОСН,СH,ОН() + ;0,(g) — 2C0,(g) + зH,О(); AH = –1189.8 kJ