Concept explainers
Determine the standard enthalpy of formation of ethanol (C2H5OH) from its standard enthalpy of combustion (−1367.4 kJ/mol).
Interpretation:
The standard enthalpy of formation of Ethanol has to be calculated.
Concept Introduction:
The change in enthalpy that is associated with the formation of one mole of a substance from its related elements being in standard state is called standard enthalpy of formation (
The standard enthalpy of reaction is the enthalpy of reaction that takes place under standard conditions.
The equation for determining the standard enthalpies of compound and element can be given by,
To calculate: The standard enthalpy of formation of Ethanol
Answer to Problem 10.130QP
The standard enthalpy of formation of Ethanol is
Explanation of Solution
Standard enthalpy of formation of
Standard enthalpy of formation of Water =
Standard enthalpy of formation of Oxygen =
The equation of formation of Ethanol from its elements can be given as,
The reverse reaction of the above equation gives the combustion of the Ethanol that can be given as,
Water is removed from the reactant side and
Standard enthalpy of formation of Ethanol=
The standard enthalpy of formation of Ethanol was calculated by using the values of standard enthalpies of reactants and the products. The standard enthalpy of formation of Ethanol is found to be
Want to see more full solutions like this?
Chapter 10 Solutions
Chemistry: Atoms First - With Solutions and Access
- Which of the enthalpies of combustion in Table 5.2 the table are also standard enthalpies of formation?arrow_forwardWhen 2.50 g of methane burns in oxygen, 125 kJ of heat is produced. What is the enthalpy of combustion per mole of methane under these conditions?arrow_forwardCompounds with carboncarbon double bonds, such as ethylene, C2H4, add hydrogen in a reaction called hydrogenation. C2H4(g)+H2(g)C2H6(g) Calculate the enthalpy change for this reaction, using the following combustion data: C2H4(g)+3O2(g)2CO2(g)+2H2O(l);H=1411kJC2H6(g)+72O2(g)2CO2(g)+3H2O(l);H=1560kJH2(g)+12O2(g)H2O(l);H=286kJarrow_forward
- The Romans used calcium oxide, CaO, to produce a strong mortar to build stone structures. Calcium oxide was mixed with water to give Ca(OH)2, which reacted slowly with CO2 in the air to give CaCO3. Ca(OH)2(s) + CO2(g) CaCO3(s) + H2O(g) (a) Calculate the standard enthalpy change for this reaction. (b) How much energy is evolved or absorbed as heat if 1.00 kg of Ca(OH)2 reacts with a stoichiometric amount of CO2?arrow_forwardA 0.470-g sample of magnesium reacts with 200 g dilute HCl in a coffee-cup calorimeter to form MgCl2(aq) and H2(g). The temperature increases by 10.9 C as the magnesium reacts. Assume that the mixture has the same specific heat as water and a mass of 200 g. (a) Calculate the enthalpy change for the reaction. Is the process exothermic or endothermic? (b) Write the chemical equation and evaluate H.arrow_forwardWhat mass of acetylene, C2H2(g), must be burned to produce 3420 kJ of heat, given that its enthalpy of combustion is 1301 kJ/mol? Compare this with the answer to Exercise 5.91 and determine which substance produces more heat per gram.arrow_forward
- The 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_forwardThe enthalpy change for the following reaction is 393.5 kJ. C(s,graphite)+O2(g)CO2(g) (a) Is energy released from or absorbed by the system in this reaction? (b) What quantities of reactants and products are assumed? (c) Predict the enthalpy change observed when 3.00 g carbon burns in an excess of oxygen.arrow_forwardA compound is 82.7% carbon and 17.3% hydrogen, and has a molar mass of approximately 60 g/mol. When 1.000 g of this compound burns in excess oxygen, the enthalpy change is 49.53 kJ. (a) What is the empirical formula of this compound? (b) What is the molecular formula of this compound? (c) What is the standard enthalpy of formation of this compound? (d) Two compounds that have this molecular formula appear in Appendix G. Which one was used in this exercise?arrow_forward
- Use standard enthalpies of formation in Appendix L to calculate enthalpy changes for the following: (a) 0.054 g of sulfur burns, forming SO2(g) (b) 0.20 mol of HgO(s) decomposes to Hg() and O2(g) (c) 2.40 g of NH3(g) is formed from N2(g) and excess H2(g) (d) 1.05 102 mol of carbon is oxidized to CO2(g)arrow_forwardThe first step in the preparation of lead from its ore (galena, PbS) consists of roasting the ore. PbS(s)+32O2(g)SO2(g)+PbO(s) Calculate the standard enthalpy change for this reaction, using enthalpies of formation (see Appendix C).arrow_forwardThe combustion of 1.00 mol liquid methyl alcohol (CH3OH) in excess oxygen is exothermic, giving 727 kJ of heat. (a) Write the thermochemical equation for this reaction. (b) Calculate the enthalpy change that accompanies the burning 10.0 g methanol. (c) Compare this with the amount of heat produced by 10.0 g octane, C8H18, a component of gasoline (see Exercise 5.41).arrow_forward
- Chemistry: Matter and ChangeChemistryISBN:9780078746376Author:Dinah Zike, Laurel Dingrando, Nicholas Hainen, Cheryl WistromPublisher:Glencoe/McGraw-Hill School Pub CoChemistry by OpenStax (2015-05-04)ChemistryISBN:9781938168390Author:Klaus Theopold, Richard H Langley, Paul Flowers, William R. Robinson, Mark BlaserPublisher:OpenStaxChemistry: The Molecular ScienceChemistryISBN:9781285199047Author:John W. Moore, Conrad L. StanitskiPublisher:Cengage Learning
- General 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 LearningChemistry: Principles and PracticeChemistryISBN:9780534420123Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward MercerPublisher:Cengage LearningChemistry & Chemical ReactivityChemistryISBN:9781337399074Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage Learning