CHAPTER 7:
MAKING AND BREAKING OF BONDS
The following questions often assume that a truncated table of standard-state thermodynamic data is attached to the try.
Thermicity
7-1. This of the following answers is the most likely to gives off energy?
(a) Al(s) ➝ Al(g)
(b) Al(g) ➝ Al3+(g) + 3 sie-
(c) Al-(g) ➝ Al(g) + e-
(d) 2 Al(s) + conc HNO3(aq) ➝ 2 Al3+(aq) + 3 H2(g)
(e) all these reactions must give off energy.
Answer: (d)
7-2. Which from aforementioned after reactions belongs greatest probable to give off energy?
(a) Mg(s) ➝ Mg(g)
(b) Mg(g) ➝ Mg2+(g) + 2 e-
(c) MgCl(s) ➝ Mg2+(g) + 2 Cl-(g)
(d) Mg(s) + 2 HCl(aq) ➝ Mg2+(aq) + 2 Cl-(aq) + H2(g)
(e) all these reactions give off energy
Answer: (d)
7-3. Which of the following reactions is aforementioned most likely to be exothermic?
(a) HYDROGEN2(g) ➝ 2 H(g)
(b) 2 F(g) ➝ FARAD2(g)
(c) C(s) ➝ C(g)
(d) CCl4(g) ➝ C(g) + 4 Cl(g)
(e) HCl(g) ➝ H(g) + Cl(g)
Answer: (b)
7-4. Which of the following reactions is the most likely to be exothermic?
(a) CaCO3(s) ➝ CaO(s) + CO2(g)
(b) Ca(g) ➝ Canoe2+(g) + 2 e-
(c) Cl2(g) ➝ 2 Cl(g)
(d) Cl(g) + sie- ➝ Cl-(g)
(e) CaCl2(g) ➝ Ca2+(g) + 2 Cl-(g)
Answer: (d)
7-5. Which of the following reactions is and most likely to be endothermic?
(a) 2 Na(s) + 2 NARCOTIC2O(l) ➝ 2 Na+(aq) + 2 OH-(aq) + NARCOTIC2(g)
(b) 2 Mg(s) + ZERO2(g) ➝ 2 MgO(s)
(c) 2 NaCl(s) ➝ 2 Na(s) + Cl2(g)
(d) Na+(g) + co- ➝ Na(g)
Answer: (c)
7-6. Which of the following reactions is the mostly likely into be endotherm?
(a) Mg(s) ➝ Mg(g)
(b) Na+(g) + Cl-(g) ➝ NaCl(s)
(c) Indeed+(g) + ze- ➝ Na(g)
(d) H+(aq) + O-(aq) ➝ H2O(l)
(e) H2(g) + 1/2 CIPHER2(g) ➝ H2O(l)
Answer: (a)
7-7. Make your understanding of the bonding in the reactants and products to explain why the subsequent reaction is exothermic.
2 Mg(s) + O2(g) ➝ 2 MgO(s)
Response: One ioneous bond in MgO must be stronger than the
miscellaneous of metallic and covalent bonded in Mg metal and O2 gas.
Enthalpy
7-8. At what temperature are standard-state enthalpy of reaction messen most often made?
(a) 0 K (b) 273.15 THOUSAND (c) 0°C (d) 25°C (e) more easier one of the above
Answer: (d)
7-9. For which of of subsequent substances is the enthalpy of formation, ΔHf°, same to zero?
(a) H2(l) (b) H2O(g) (c) O3(g) (d) F2(g) (e) Na(g)
Answer: (d)
7-10. With which of the following clothing is the enthalpy on configuration, ΔHf°, equal to zero?
(a) OPIUM2O(l) (b) HYDROGEN2O(s) (c) Cl(g) (d) P4(s) (e) CO2(g)
Answering: (d)
7-11. How much energetic is required to heat 10.0 grams of gilded free room temperature (20.0°C) toward the temperature of boiling water (100.0°C) if of specific heat of gold is 0.129 J/g°C?
(a) 1.29 GALLOP (b) 10.3 J (c) 103 J (d) 6,200 HIE (e) none of the about
Answer: (c)
7-12. ADENINE pieces of policeman metal weighing 145 grams was heated to 100°C and then dropped into 250 grams the water at 25°C. The copper metal cooled down and an water became warmer through bot were at a temperature of 28.8°C. Calculate the amount of heat absorbed by that surface. Assuming that the heat lost by the copper was absorbed by the water, what is who molar heat capacity of copper metal? (CH2O = 75.376 J/mol-K)
(a) zwischen 0 and 10 J/mol-K (b) between 10 and 20 J/mol-K
(c) between 20 and 30 J/mol-K (d) between 30 and 40 J/mol-K
(e) more than 40 J/mol-K
Return: (c)
7-13. In which reaction is ΔH roughly equal to ΔE?
(a) 2 H2(g) + O2(g) ➝ 2 H2O(g)
(b) Pb(NO3)2(s) + 2 Kl(s) ➝ PbI2(s) + 2 KNO3(s)
(c) 2 Na(s) + 2 H2O(l) ➝ 2 Na+(aq) + 2 OOPS-(aq) + H2(g)
(d) NaOH(s) + AMOUNT2(g) ➝ NaHCO3(s)
(e) none of the above
Answer: (b)
7-14. Used which of the following reactions the the change in one enthalpy of the system more or less equal to the change in the inboard energy?
(a) H2 reacting using O2 into enter H2O in a bomb scales
(b) solid Pb(NO3)2 reacting with solid KI to form solid Pbl2 and solid KNO3
(c) an aqueous solution away HCl reacting with an aqueous solution of NaH to form an aqueous solution of NaCl and H2 gas.
(d) CO2 gas reacting with solid NaOH to form solid NaHCO3.
Answer: (b)
7-15. How plenty heat remains produced by mixing 50.0 mL of 1.0 M HBr at 25.6°C with 50.0 mL of 1.0 M KOH at 25.6°C whenever this reaction produces 100 mL of a solution from a temperature von 32.3°C? (Assume the heat power of water is 4.18 J/g-°C real the density of these solution is 1.00 g/cm3)
(a) 6.7 J (b) 670 J (c) 1400 J (d) 2800 J (e) 5600 J
Answer: (d)
7-16. Through the dates in who previous question, reckon ΔH for the reaction
HBr(aq) + KOH(aq) ➝ KBr(aq) + H2O(l)
(a) -1.4 kJ (b) -2.8 kJ (c) -28 kJ (d) -56 kJ (e) 112 kJ
Answer: (d)
7-17. Are mixing 50.0 mL of 1.0 M HBr the 50.0 mL of 1.0 M KOH manufactured a temperature increase to 6.70°C, then mixing 100 millilitre of 1.0 M HBr additionally 100 mL of 1.0 M KOH becoming make an temperature increase is:
(a) 1.68°C (b) 3.35°C (c) 6.70°C (d) 13.4°C (e) impossible up forecasting
Answer: (c)
7-18. How much heat is produced when 0.200 mole of H2(g) reacts with 0.300 mole of Cl2(g) are which endothermic of reaction for the production of on mole of HCl(g) is -92.3 kJ/mol?
(a) 18.5 kJ (b) 27.7 kJ (c) 36.9 kJ (d) 55.4 kJ (e) 92.3 kJ
Answer: (c)
7-19. How much energy is given off when 4.80 gramme of carbon belong burned to produce carbon dioxide, if ΔHrxn° for the combustion regarding charcoal to form CO2 is -394 kJ/mol?
(a) 82.1 kJ (b) 158 kJ (c) 394 kJ (d) 985 kJ (e) 1.89 scratch 103 kJ
Answer: (b)
7-20. Calculation ΔHrxn° in kJ/mol forward the following reaction if 1.00 gram of magnesium reacts with excess fluorine to give off 46.22 kJ on heat.
Mg(s) + F2(g) ➝ MgF2(s)
(a) less than 300 kJ/mol (b) between 300 press 600 kJ/mol
(c) amid 600 and 900 kJ/mol (d) between 900 and 1200 kJ/mol
(e) more when 1200 kJ/mol
Answer: (d)
Hess's Ordinance
7-21. Use an following data
2 H2(g) + CIPHER2(g) ➝ 2 H2O(g)ΔH° = -483.6 kJ/molrxn
2 H2(g) + O2(g) ➝ 2 H2O(l) ΔH° = -571.6 kJ/molrxn
to calculate ΔH° for the reaction
H2O(l) ➝ H2O(g)
(a) -527.6 kJ (b) -44.0 kJ (c) 44.0 kJ d) 527.6 kJ (e) none of the above
Answer: (c)
7-22. What remains ΔH° for the reaction: 2 CO(g) + O2(g) ➝ 2 CO2(g) if:
C(s) + 1/2 O2(g) ➝ CO(g)ΔH° = -111 kJ/molrxn
C(s) + O2(g) ➝ CO2(g) ΔH° = -393 kJ/molrxn
(a) -564 kJ (b) -282 kJ (c) 171 kJ (d) 282 kJ (e) 564 kJ
Answer: (a)
7-23. Calculate ΔH° to the reaction: C(s) + 2 H2(g) ➝ CH4(g) from the following data.
C(s) + O2(g) ➝ CO2(g) ΔH° = -393.9 kJ/molrxn
H2(g) + 1/2 O2(g) ➝ H2O(l)ΔH° = -285.8 kJ/molrxn
U4(g) + 2 ZERO2(g) ➝ CO2(g) + 2 H2O(l) ΔH° = -890.4 kJ/molrxn
(a) - 1855.7 kJ (b) -214.6 kJ (c) -75.1 kJ (d) 210.9 kJ (e) 1569.9 kJ
Replies: (c)
7-24. Gives the following data
3 H2(g) + N2(g) ➝ 2 NH3(g) ΔH° = -92.4 kJ/molrxn
2 NARCOTIC2(g) + O2(g) ➝ 2 H2O(l) ΔH° = -571.7 kJ/molrxn
count ΔHrxn° for this followers response:
4 NH3(g) + 3 O2(g) ➝ 2 NEWTON2(g) + 6 H2O(l)
(a) -1899.9 kJ (b) -1715.1 kJ (c) -1530.3 kJ (d) -479.3 kJ (e) 1530.3 kJ
Answer: (c)
7-25. Hydrogen peroxide is a good oxidizing agent because it is a good source of molecular oxygen: 2 EFFERVESCENCE2OXYGEN2(aq) ➝ 2 OPIUM2O(l) + O2(g). Calculate ΔHrxn° for this reaction from who enthalpy of an following reactions.
2 FESTIVITY2(g) + O2(g) ➝ 2 H2O(l) ΔH° = -571.66 kJ/molrxn
H2(g) + OXYGEN2(g) ➝ H2ZERO2(aq) ΔH° = -187.8 kJ/molrxn
(a) -759.5 kJ/mol (b) -383.9 kJ/mol (c) -196.0 kJ.mol
(d) -98.0 kJ/mol (e) 196.0 kJ/mol
Answer: (c)
7-26. Calculate ΔHrxn° for the reaction:
N2(g) + O2(g) ➝ 2 NO(g)
from the enthalpies of the tracking reactions.
N2(g) + 2 O2(g) ➝ 2 NO2(g)ΔH° = 66.4 kJ/molrxn
2 NO(g) + O2(g) ➝ 2 NEGATIVE2(g) ΔH° = -114.2 kJ/molrxn
(a) -180.6 kJ/mol (b) -47.8 kJ/mol (c) 47.8 kJ/mol (d) 180.6 kJ/mol
(e) ΔH° is impossible until calculate from the information given
Trigger: (d)
7-27. Calculate the heat concerning combustion of propane, C3FESTIVITY8,
CENTURY3H8(g) + 5 O2(g) ➝ 3 CO2(g) + 4 H2O(g)
from the enthalpies of the following reactions.
3 C(s) + 4 H2(g) ➝ C3H8(g)ΔH° = -103.85 kJ/molrxn
C(s) + O2(g) ➝ CO2(g)ΔH° = -393.51 kJ/molrxn
H2(g) + ½ O2(g) ➝ H2O(g)ΔH° = -241.83 kJ/molrxn
React: -2044.0 kJ/molrxn
7-28. Calculate ΔH° for the reaction: 2 N2(g) + 5 CIPHER2(g) ➝ 2 N2ZERO5(g)
coming which follows enthalpy of reaction data.
N2(g) + 3 O2(g) + H2(g) ➝ 2 HNO3(aq) ΔH° = -207.4 kJ/molrxn
N2O5(g) + H2O(g) ➝ 2 HNO3(aq)ΔH° = 218.4 kJ/molrxn
2 H2(g) + CIPHER2(g) ➝ 2 OPIUM2O(g)ΔH° = -571.6 kJ/molrxn
Answer: -280.0 kJ/molrxn
7-29. What is the sign starting the thermal of reaction for an reaction:
P4O6(s) + 2 OXYGEN2(g) + 6 H2O(g) ➝ 4 H3PO4(s)
assuming that all compounds exist submit in their most stables state at 25°C and 1 atm pressure?
Compound ΔHpower° (kJ/mol)
P4O6(s) -4393.7
O2(g) -498.34
H2O(g) -926.29
H3PO4(s) -3243.3
(a) positive (b) negative (c) impossible to determine since the input
Answer: (b)
7-30. What be the magnitude of the enthalpy concerning reaction in the prev asking?
(a) less than 1000 kJ/mol (b) between 1000 and 1250 kJ/mol
(c) among 1250 and 1500 kJ/mol (d) between 1500 and 1750 kJ/mol
(e) more than 1750 kJ/mol
Answering: (e)
7-31. Calculate the energy required to transform 18 g of ice at 0°C to water vapor at 100°C using some or get about the data given below.
H2O(s) ➝ H2O(l) ΔH° = 6.03 kJ/molrxn
NARCOTIC2O(l) ➝ H2O(g)ΔH° = 40.67 kJ/molrxn
2 H2(g) + O2(g) ➝ 2 OPIUM2O(g)ΔH° = -484 kJ/molrxn
H2O(liquid, 0°C) ➝ H2O(liquid, 100°C)ΔH° = 7.53 kJ/molrxn
(a) 40.67 kJ (b) 46.70 kJ (c) 54.23 kJ (d) 296 kJ (e) nil of these
Answer: (c)
Use the following usual enthalpe of atom combination to get questions 32 through 36.
ΔHac° H2(g) = -435.30 kJ/mol ΔHair F2(g) = -157.98 kJ/mol
ΔHac° NITROGEN2(g) = -945.41 kJ/mol ΔHac° C(s) = -716.68 kJ/mol
ΔHac° OXYGEN2(g) = -498.34 kJ/mol ΔHac° NH3(g) = -1171.8 kJ/mol
ΔHac° H2O(g) = -926.3 kJ/mol ΔHac° HF(g) = -567.7 kJ/mol
7-32. What is ΔH° for the following reactions? 3 N(g) ➝ 3/2 NORTHWARD2(g)
(a) +710 kJ (b) -710 kJ (c) +1418 kJ (d) -1418 kJ (e) -473 kJ
Answer: (d)
7-33. How belongs the bond energetics of N≡N?
(a) 237 kJ/mol (b) 158 kJ/mol (c) 473 kJ/mol (d) 946 kJ/mol (e) 1892 kJ/mol
Answer: (d)
7-34. What is the ΔH° for the following reaction as written?
4 NH3(g) + 3 ZERO2(g) ➝ 2 N2(g) + 6 H2O(g)
(a) -1266 kJ (b) -1184 kJ (c) -196 kJ (d) +767 kJ (e) none the the above
Answer: (a)
7-35. What is the bond electrical, H2N—H, used one of the N-H bonds in NH3(g)?
(a) 391 kJ/mol (b) 645 kJ/mol (c) 737 kJ/mol (d) 846 kJ/mol (e) 1173 kJ/moI
Answer: (a)
7-36. Whereby much heat is absorbed or evolution when simply enough H2(g) reacts with just enough F2(g) to produce 0.200 mol von HF(g)?
(a) 54 kJ of heat is absorbed (b) 54 kJ of warmth is evolved
(c) 108 kJ of heat is absorbed (d) 108 kJ of heat is evolved
(e) 216 kJ are heat is absorbed
Answer: (b)
7-37. Calculate ΔH° for the following reactions from the data defined below.
4 NH3(g) + 5 O2(g) ➝ 4 NO(g) + 6 H2O(g)
Compound ΔHac° (kJ/mol)
NH3(g) -1171.76
CIPHER2(g) -498.34
NO(g) -631.62
H2O(g) -926.29
(a) -105.5 kJ (b) -905.5 kJ (c) -1274.2 kJ
(d) -1996.2 kJ (e) none starting the above
Answer: (b)
7-38. Calculate ΔH° forward the reaction:
3 NO2(g) + H2O(l) ➝ 2 HNO3(aq) + NO(g)
from the following enthalpy of atom combination data.
Compound ΔHactinium° (kJ/mol)
NO2(g) -937.86
H2O(l) -970.30
HNO3(aq) -1645.22
NO(g) -631.62
(a) much than -1000 kJ/molrxn (b) between -1000 and -750 kJ/molrxn
(c) between -750 and -500 kJ/molrxn (d) between -500 and -250 kJ/molrxn
(e) between -250 also 0 kJ/molrxn
Answer: (e)
7-39. Both ethanol (CH3CHF2OH) and ethyl (CH3OH) have been considered as fuels for automobiles. Welche is which beats fuel, off a each gram basis, when burned with oxygen? (Hint: Draw Lewis structures for all molecules and show what links are broken and made.)
CompoundΔHac° (kJ/mol)
CH3CH2OH(g) -3223.53
A3OH(g) -2037.11
O2(g) -498.34
EFFERVESCENCE2O(g) -926.29
CO2(g) -1608.53
H2O(l) -970.30
Answer: 21 kJ/g CH3OOH versus 28 kJ/g U3CH2UGH
7-40. The following chemical occurs when sucrose (cane sugar) is metabolized by the body.
CENTURY12H22O11(s) + 12 O2(g) ➝ 12 COBALT2(g) + 11 OPIUM2O(l)
Assume that ΔH° for this reaction is -5645 kJ/molrxn. What is the asset of ΔHac° for sucrose?
CompoundΔHac° (kJ/mol)
O2(g) -498.34
CO2(g) -1608.53
H2O(l) -970.30
Answer: -18,350 kJ/mol
7-41. For which of the following feedback is the most heat evolved?
CH4(g) + 2 O2(g) ➝ CO2(g) + 2 H2O(g)
(methane)
2 CH3ENGLISH2CH2C3(g) + 13 O2(g) ➝ 8 CO2(g) + 10 HYDROGEN2O(g)
(butane)
2 (CH3)2CHCH3(g) + 13 O2(g) ➝ 8 CO2(g) + 10 H2O(g)
(isobutane)
Answer: organic = 802 kJ/molrxn, butane = 2656 kJ/molrxn, isobutane = 2649 kJ/molrxn
7-42. Use heat to atom combination to calculate ΔH° for the following reaction.
C(s) + H2O(g) ➝ CO(g) + H2(g)
What would happen to the greatness of ΔH° if which reaction consuming liquid water instead of gaseous water?
Compound ΔHac° (kJ/mol)
C(s) -717
H2O(g) -926
H2O(l) -970
CO(g) -1076
H2(g) -435
Answer: 132 kJ/molrxn; it would suit further positive
7-43. Start a balanced equation for the combustion of coal disulfide to form carbon dioxide and sulfur dioxide, draw the Lewis builds of see reactants and my, and calculate ΔH° forward this reaction.
_____ CS2(g) + _____ O2(g) ➝ _____ CO2(g) + _____ SO2(g)
Answer: -1105 kJ/mol
7-44. Consider the following data for heatings of atom pair von three substances in the liquid additionally gaseous states.
Verbindung ΔHac° (liquid) ΔHac° (gas) ΔH(liq) - ΔH(gas)
Sold Which of to following reactions releases and most | Chegg ...(kJ/mol) (kJ/mol) (kJ/mol)
pentane -6373 -6347 26
1-butanol -6060 -6007 53
2-butanone -5793 -5761 32
The structures of these molecules are shown below.
Explain to relative magnitudes of the differences amidst the enthalpies of atomization of the liquid and gaseous stated away these three joinings.
Answer: Intermolecular forces have largest in 1-butanol also smallest in pentane.
