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(a)
Interpretation: The enthalpy of combustion of ethanol and isooctane, the fuel which release more
Concept introduction:
Enthalpy of combustion: At standard conditions when one mole of substance is burnt completely in presence of oxygen, the enthalpy change involved is called enthalpy of combustion.
(a)
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Answer to Problem 47GQ
Isooctane release more energy than ethanol.
Explanation of Solution
Given the combustion of ethanol and isooctane:
Enthalpy of combustion can be calculated by the equation:
Enthalpy of combustion can be calculated by the equation:
Isooctane releases more energy per kilogram.
(b)
Interpretation: compare the enthalpy of combustion of ethanol and isooctane and the fuel which release more
Concept introduction:
Enthalpy of combustion: At standard conditions when one mole of substance is burnt completely in presence of oxygen, the enthalpy change involved is called enthalpy of combustion.
(b)
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Answer to Problem 47GQ
Ethanol produces less
Explanation of Solution
One mole of ethanol produces two moles of
The number of moles
One mole of isooctane produces eight moles of
The number of moles
Isooctane release more amount of
(c)
Interpretation: The better fuel in terms of energy production and greenhouse gases should be determined.
Concept introduction:
Enthalpy of combustion: At standard conditions when one mole of substance is burnt completely in presence of oxygen, the enthalpy change involved is called enthalpy of combustion.
(c)
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Answer to Problem 47GQ
Isooctane releases more energy, but it releases more
Explanation of Solution
In-order to say whether ethanol or isooctane is a better fuel, we have to compare its energy release.
Comparing ethanol and isooctane, isooctane releases more energy.
But the problem is that when we compare the
On the basis of energy release isooctane can be considered as a better fuel, but when the release of
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Chapter 20 Solutions
Chemistry & Chemical Reactivity
- From the data given in Appendix I, determine the standard enthalpy change and the standard free energy change for each of the following reactions: (a) BF3(g)+3H2O(l)B(OH)3(s)+3HF(g) (b) BCl3(g)+3H2O(l)B(OH)3+3HCl(g) (c) B2H6(g)+6H2O(l)2B(OH)3(s)+6H2(g)arrow_forwardActually, the carbon in CO2(g) is thermodynamically unstable with respect to the carbon in calcium carbonate(limestone). Verify this by determining the standardGibbs free energy change for the reaction of lime,CaO(s), with CO2(g) to make CaCO3(s).arrow_forwardWhen 7.11 g NH4NO3 is added to 100 mL water, the temperature of the calorimeter contents decreases from 22.1 C to 17.1 C. Assuming that the mixture has the same specific heat as water and a mass of 107 g, calculate the heat q. Is the dissolution of ammonium nitrate exothermic or endothermic?arrow_forward
- The value of G for the reaction 2C4H10(g)+13O2(g)8CO2(g)+10H2O(l) is 5490. kJ. Use this value and data from Appendix 4 to calculate the standard free energy of formation for C4H 10(g).arrow_forwardConsider the Haber process: N2(g)+3H2(g)2NH3(g);H=91.8kJ The density of ammonia at 25C and 1.00 atm is 0.696 g/L. The density of nitrogen, N2, is 1.145 g/L, and the molar heat capacity is 29.12 J/(mol C). (a) How much heat is evolved in the production of 1.00 L of ammonia at 25C and 1.00 atm? (b) What percentage of this heat is required to heat the nitrogen required for this reaction (0.500 L) from 25C to 400C, the temperature at which the Haber process is run?arrow_forwardUsing values of fH and S, calculate rG for each of the following reactions at 25 C. (a) 2 Na(s) + 2 H2O() 2 NaOH(aq) + H2(g) (b) 6 C(graphite) + 3 H2(g) C6H6() Which of these reactions is (are) predicted to be product-favored at equilibrium? Are the reactions enthalpy- or entropy-driven?arrow_forward
- 9.68 What are some features of petroleum that make it such an attractive fuel?arrow_forwardThe combustion of methane can be represented as follows: a. Use the information given above to determine the value of H for the combustion of methane to form CO2(g) and 2H2O(l). b. What is Hf for an element in its standard state? Why is this? Use the figure above to support your answer. c. How does H for the reaction CO2(g) + 2H2O (1) CH4(g) + O2(g) compare to that of the combustion of methane? Why is this?arrow_forwardThere are millions of organic compounds known, and new ones are being discovered or made at a rate of morethan 100,000 compounds per year. Organic compoundsburn readily in air at high temperatures to form carbondioxide and water. Several classes of organic compoundsare listed, with a simple example of each. Write a balanced chemical equation for the combustion in O2ofeach of these compounds, and then use the data inAppendix J to show that each reaction is product-favoredat room temperature. From these results, it is reasonable to hypothesize thatallorganic compounds are thermodynamically unstable inan oxygen atmosphere (that is, their room-temperaturereaction with O2(g) to form CO2(g) and H2O() isproduct-favored). If this hypothesis is true, how canorganic compounds exist on Earth?arrow_forward
- In the late eighteenth century Priestley prepared ammonia by reacting HNO3(g) with hydrogen gas. The thermodynamic equation for the reaction is HNO3(g)+4H2(g)NH3(g)+3H2O(g)H=637kJ (a) Calculate H when one mole of hydrogen gas reacts. (b) What is H when 10.00 g of NH3(g) are made to react with an excess of steam to form HN3(g) and H2 gases?arrow_forwardAt 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_forwardUse the appropriate tables to calculate H for (a) the reaction between copper(II) oxide and carbon monoxide to give copper metal and carbon dioxide. (b) the decomposition of one mole of methyl alcohol (CH3OH) to methane and oxygen gases.arrow_forward
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