Chemistry for Engineering Students
4th Edition
ISBN: 9781337398909
Author: Lawrence S. Brown, Tom Holme
Publisher: Cengage Learning
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Textbook Question
Chapter 9, Problem 9.77PAE
9.77 When a reaction is exothermic, is the sum of bond energies of products or of reactants greater?
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Using bond energies to estimate enthalphy (or H) of the reaction, if a reaction is exothermic then the energy needed to break the bonds was __________ the energy released to form the new bonds.
1) less than
2)More than
3) equal to
Use average bond energies to estimate the enthalpy changes of the following reaction? 2HF-->H2 + F2
a. -466kJ
b. +38.6kJ
c, -413kJ
d. -93kJ
Balance the following thermochemical equation with the lowest whole number coefficients, then use the table of bond enthalpies to determine:A) the enthalpy of reaction, ΔrH∘. B) heat exchanged when 39.86 g of Cl2(g) reacts (assume it is the limiting reactant).
Reaction: C2N2(g)+Cl2(g)⟶NCl3(g)+CCl4(g)
Bond Bond Energy (kJ/mol) Bond Bond Energy (kJ/mol)C-C 347 C=O (in CO2) 799C=C 614 C=O 745C≡C 839 C≡O 1070C-H 413 O=O 498O-H 467 N-H 391H-H 432 N≡N 945C-O 358 N-Cl 200C-N 305 N-O 201C-Cl 339 C≡N 891Cl-Cl 243 S-Cl 250S=O 535 S-S 215S-O 364 S-H 339
Chapter 9 Solutions
Chemistry for Engineering Students
Ch. 9 - Explain the economic importance of conversions...Ch. 9 - • define work and beat using the standard sign...Ch. 9 - • define state functions and explain their...Ch. 9 - • state the first law of thermodynamics in words...Ch. 9 - • use calorimetric data to obtain values for E and...Ch. 9 - • define Hfo and write formation reactions for...Ch. 9 - • explain Hess’s law in your own words.Ch. 9 - • calculate H for chemical reactions from...Ch. 9 - Prob. 9.1PAECh. 9 - Prob. 9.2PAE
Ch. 9 - Prob. 9.3PAECh. 9 - Prob. 9.4PAECh. 9 - Prob. 9.5PAECh. 9 - Prob. 9.6PAECh. 9 - Define the term internal energy.Ch. 9 - How fast (in meters per second) must an iron ball...Ch. 9 - What is the kinetic energy of a single molecule of...Ch. 9 - 9.10 The kinetic energy of molecules is often used...Ch. 9 - 9.11 Analyze the units of the quantity...Ch. 9 - 9.12 How many kilojoules are equal to 3.27 L atm...Ch. 9 - Prob. 9.13PAECh. 9 - Prob. 9.14PAECh. 9 - 9.15 Carry out the following conversions of energy...Ch. 9 - 9.16 According to Figure 9.2, the total energy...Ch. 9 - 9.17 If a machine does 4.8103kJ of work after an...Ch. 9 - 9.18 Calculate (a) q when a system does 54J of...Ch. 9 - 9.19 If the algebraic sign of E is negative, in...Ch. 9 - 9.20 State the first law of thermodynamics briefly...Ch. 9 - 9.21 Which type of energy heat or work, is valued...Ch. 9 - 9.12 PV-work occurs when volume changes and...Ch. 9 - 9.23 Which system does not work: (a) E=436J ,...Ch. 9 - 9.29 In which case is heat added to the system:...Ch. 9 - Prob. 9.25PAECh. 9 - 9.26 Gas furnaces have achieved impressive...Ch. 9 - Prob. 9.27PAECh. 9 - 9.28 When an electrical appliance whose power...Ch. 9 - Prob. 9.29PAECh. 9 - 9.30 For the example of shallow water and sandy...Ch. 9 - 9.31 A metal radiator is made from 26.0 kg of...Ch. 9 - 9.32 The material typically used to heat metal...Ch. 9 - 9.33 Copper wires used to transport electrical...Ch. 9 - 9.34 A copper nail and an iron nail of the same...Ch. 9 - 9.35 A piece of titanium metal with a mass of 20.8...Ch. 9 - 9.36 Define the term calibration.Ch. 9 - 9.37 A calorimeter contained 75.0 g of water at...Ch. 9 - 9.38 The energy densities of various types of coal...Ch. 9 - 9.39 How much thermal energy is required to heat...Ch. 9 - Prob. 9.40PAECh. 9 - 9.41 Under what conditions does the enthalpy...Ch. 9 - 9.42 Why is enthalpy generally more useful than...Ch. 9 - Prob. 9.43PAECh. 9 - Prob. 9.44PAECh. 9 - 9.45 What happens to the temperature of a material...Ch. 9 - 9.46 The heat of fusion of pure silicon is 43.4...Ch. 9 - 9.47 If 14.8 kJ of heat is given off when 1.6 g of...Ch. 9 - 9.48 Calculate the energy required to convert 1.70...Ch. 9 - 9.49 Hvap=31.3 kJ/mol for acetone. If 1.40 kg of...Ch. 9 - 9.50 When a 13.0-g sample of NaOH(s) dissolves in...Ch. 9 - Prob. 9.51PAECh. 9 - 9.52 Write the formation reaction for each of the...Ch. 9 - 9.53 Using these reactions, find the standard...Ch. 9 - 9.54 The phase change between graphite and diamond...Ch. 9 - 9.55 Hydrogen gas will react with either acetylene...Ch. 9 - 9.56 Using heats of formation tabulated in...Ch. 9 - 9.57 The heat of combustion of butane is —2877...Ch. 9 - 9.58 For the reaction C2H2(g)+2H2(g)C2H6,H=136 kJ....Ch. 9 - 9.59 For the reaction N2(g)+O2(g)2NO(g),H=180.5kJ...Ch. 9 - 9.60 Nitroglycenne, C3H5(NO3)3( l ), is an...Ch. 9 - 9.61 Silane, SiH4, burns according to the...Ch. 9 - 9.62 Sulfur trioxide can be removed from the...Ch. 9 - 9.63 Reactions of hydrocarhons are often studied...Ch. 9 - Prob. 9.64PAECh. 9 - 9.65 When 0.0157 g of a compound with a heat of...Ch. 9 - Prob. 9.66PAECh. 9 - Prob. 9.67PAECh. 9 - 9.68 What are some features of petroleum that make...Ch. 9 - 9.69 How are the roles of transmission substations...Ch. 9 - 9.70 Residential electric service in the United...Ch. 9 - 9.71 In recent years, the notion of a “smart grid”...Ch. 9 - 9.72 Although it can be a nuisance when a laptop...Ch. 9 - 9.73 Without looking up any numerical data or...Ch. 9 - 9.74 Without looking up any numerical data or...Ch. 9 - 9.75 Explain why each of the following chemical...Ch. 9 - 9.76 Which of the following are state functions?...Ch. 9 - 9.77 When a reaction is exothermic, is the sum of...Ch. 9 - Prob. 9.78PAECh. 9 - Prob. 9.79PAECh. 9 - Prob. 9.80PAECh. 9 - 9.81 A substance has the following properties:...Ch. 9 - 9.82 The specific heat of gold is 0.13 J g-1 K-1...Ch. 9 - 9.83 A student performing a calorimetry experiment...Ch. 9 - 9.84 Some claim it would be more logical to use...Ch. 9 - 9.85 The figure below shows a "self-cooling"...Ch. 9 - 9.86 You make some iced tea by dropping 134 g of...Ch. 9 - 9.87 What will be the final temperature of a...Ch. 9 - Prob. 9.88PAECh. 9 - 9.89 A sample of gas is 80.0% CH4 and 20.0% C2H6...Ch. 9 - 9.90 Many engineering designs must incorporate...Ch. 9 - 9.91 You want to heat the air in your house with...Ch. 9 - Prob. 9.92PAECh. 9 - Prob. 9.93PAECh. 9 - Prob. 9.94PAECh. 9 - 9.95 How much heat is required to convert 250 g of...Ch. 9 - 9.96 Most first aid "cold packs" are based on the...Ch. 9 - 9.97 Suppose that the working fluid inside an...Ch. 9 - 9.98 Hydrogen combines with oxygen in fuel cells...Ch. 9 - 9.99 The chemical reaction...Ch. 9 - 9.100 Two baking sheets are made of different...Ch. 9 - Prob. 9.101PAECh. 9 - 9.102 A runner generates 418 kJ of energy per...Ch. 9 - 9.103 One reason why the energy density of a fuel...Ch. 9 - 9.104 An engineer is using sodium metal as a...Ch. 9 - Prob. 9.105PAECh. 9 - Prob. 9.106PAECh. 9 - Prob. 9.107PAECh. 9 - Prob. 9.108PAECh. 9 - Prob. 9.109PAECh. 9 - Prob. 9.110PAE
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- In general the higher the charge on the ions in an ionic compound, the more favorable the lattice energy. Why do some stable ionic compounds have +1 charged ions even though +4, + 5, and +6 charged ions would have a more favorable lattice energy?arrow_forwardExplain the decomposition of nitroglycerin in terms of relative bond enthalpies.arrow_forwardhat is the enthalpy change for a process? Is enthalpy a state function? In what experimental apparatus are enthalpy changes measured?arrow_forward
- Calculate the enthalpy of reaction for HCN(g)H(g)+C(g)+N(g) from enthalpies of formation (see Appendix C). Given that the CH bond enthalpy is 411 kJ/mol, obtain a value for the CN bond enthalpy. Compare your result with the value given in Table 9.5.arrow_forwardDraw a curve that describes the energy of a system with H and Cl atoms at varying distances. Then, find the minimum energy of this curve two ways. (a) Use the bond energy found in Table 8.1 to calculate the energy for one single HCl bond (Hint: How many bonds are in a mole?) (b) Use the enthalpy of reaction and the bond energies for H2 and Cl2 to solve for the energy of one mole of HCl bonds. H2(g)+Cl2(g)2HCl(g)Hrxn=184.7kJ/molarrow_forwardA commercial process for preparing ethanol (ethyl alcohol), C2H5OH, consists of passing ethylene gas. C2H4, and steam over an acid catalyst (to speed up the reaction). The gas-phase reaction is Use bond enthalpies (Table 9.5) to estimate the enthalpy change for this reaction when 37.0 g of ethyl alcohol is produced.arrow_forward
- Compare your answers from parts a and b of Exercise 69 of Chapter 3 with H values calculated for each reaction using standard enthalpies of formation in Appendix 4. Do enthalpy changes calculated from bond energies give a reasonable estimate of the actual values?arrow_forwardThe lattice energy of KF is 794 kJ/mol, and the interionic distance is 269 pm. The Na—F distance in NaF, which has the same structure as KF, is 231 pm. Which of the following values is the closest approximation of the lattice energy of NaF: 682 kJ/mol, 794 kJ/mol, 924 kJ/mol, 1588 kJ/mol, or 3175 kJ/mol? Explain your answer.arrow_forwardWhich statement(s) is/are true about bond enthalpy? (a) The bond energy for a triple bond between A and B is three times that of a single bond between A and B. (b) H for the breaking of a bond is always a negative number. (c) Energy is required to make a bond. (d) Bond enthalpy is defined only for bonds broken or formed in the gaseous state. (e) The presence of bonds does not influence the geometry of a molecule. However, the presence of bonds affects the value of the bond enthalpy between two atoms.arrow_forward
- With a platinum catalyst, ammonia will burn in oxygen to give nitric oxide, NO. 4NH3(g)+5O2(g)4NO(g)+6H2O(g);H=906kJ What is the enthalpy change for the following reaction? NO(g)+32H2O(g)NH3(g)+34O2(g)arrow_forwardUse bond enthalpies in Table 5.4 to estimate ΔH for each ofthe following reactions:arrow_forwardUse average bond energies to calculate ΔH for the reaction of H2 and O2 to form water.arrow_forward
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