Combination of two Equation - Shailendra Kumar Chemistry

PHYSICAL CHEMISTRY
By: Shailendra Kumar
PHYSICAL CHEMISTRY
by: SHAILENDRA KR.
Classes at: -
Meq. Approach
SCIENCE TUTORIALS; Opp. Khuda Baksh Library, Ashok Rajpath, Patna
PIN POINT STUDY CIRCLE; House No. 5A/65, Opp. Mahual Kothi, Alpana Market, Patna
Topic: Combination of Two Equations
1. Calculate ∆H°C/kJ for the following reaction using the listed standard enthalpy of reaction data:
(C 2
H 5
) 2
O (l) → C 4
H 9
OH (l)
C 4
H 9
OH (l) + 6 O 2
(g) → 4 CO 2
(g) + 5 H 2
O (g)
∆H°/kJ = -2456.1 kJ
(C 2
H 5
) 2
O (l) + 6 O 2
(g) → 4 CO 2
(g) + 5 H 2
O (g) ∆H°/kJ = -2510.0 kJ
a) -4966.1 b) -53.9
c) +53.9 d) +4966.1
e) -2483.1
2. Given the following equations and ∆H° values, determine the heat of reaction at 298 K for the
reaction:
4 HCl (g) + O 2
(g) → 2 H 2
O (g) + 2 Cl 2
(g)
H 2
(g) + Cl 2
(g) → 2 HCl (g) ∆(kJ) = -185
2 H 2
(g) + O 2
(g) → 2 H 2
O (g) ∆(kJ) = -484
a) +669 b) -114
c) -299 d) +114
e) +299
3. Given the following equations and ∆H° values, determine the heat of reaction (kJ) at 298 K for the
reaction :
CuCl 2
2 (s) + Cu (s) → 2 CuCl(s)
Cu (s) + Cl 2
(g) → CuCl 2
(s) ∆H°/kJ = -206
2 Cu (s) + Cl 2
(g) → 2 CuCl (s) ∆H°/kJ = -136
a) +35 b) +70
c) +342 d) -70
e) -342
4. Given the following equations and ∆H° values, determine the heat of reaction at 298 K for the
reaction :
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C 2
H 4
(g) + 6 F 2
(g) → 2 CF 4
(g) + 4 HF (g)
H 2
(g) + F 2
(g) → 2 HF (g) ∆H°/kJ = -537
C (s) + 2 F 2
(g) → CF 4
(g) ∆H°/kJ = -680
2 C (s) + 2 H 2
(g) → C 2
H 4
(g) ∆H°/kJ = +52.3
a) +2486 b) -2486
c) -2132 d) +1165
e) -1165
5. Given the following equations and ∆H° values, determine the heat of reaction at 298 K for the
reaction :
C (s) + 2 H 2
(g) → CH 4
(g)
C (s) + O 2
(g) → CO 2
(g) ∆H°/kJ = -393.5
H 2
(g) + 1/2 O 2
(g) → H 2
O (l) ∆H°/kJ = -285.8
CO 2
(g) + 2 H 2
O (l) → CH 4
(g) + 2 O 2
(g) ∆H°/kJ = +890.3
a) -192.2 b) -74.8
c) +74.8 d) +211.0
e) -211.0
6. Given the following equations and ∆H° values, determine the heat of reaction at 298 K for the
reaction which occurs in a welder’s acetylene torch:
2 C 2
H 2
(g) + 5 O 2
(g) → 4 CO 2
(g) + 2 H 2
O (l)
H 2
(g) + 1/2 O 2
(g) → H 2
O (l) ∆H°/kJ = -285.8
2 C (s) + H 2
(g) → C 2
H 2
(g) ∆H°/kJ = +226.7
C (s) + O 2
(g) → CO 2
(g) ∆H°/kJ = -393.5
a) -571.6 b) -2599.0
c) -1574.0 d) -2145.6
e) -285.8
7. Given the following equations and ∆H° values, determine the heat of reaction (kJ) at 298 K for the
reaction:
2 NF 3
(g) + Cu (s) → N 2
F 4
(g) + CuF 2
(s)
2 NF 3
(g) + 2 NO (g) → N 2
F 4
(g) + 2 NOF (g) ∆H°/kJ = -82.9
NO (g) + 1/2 F 2
(g) → NOF (g) ∆H°/kJ = -156.9
Cu (s) + F 2
(g) → CuF 2
(g) ∆H°/kJ = -531.0
a) +770.8 b) +291.2
c) -291.6 d) -300.1
e) -605.0
8. Calculate the standard enthalpy change (kJ) for the following reaction of nitrogen dioxide with
water:
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3 NO 2
(g) + H 2
O (l) → 2 HNO 3
(aq) + NO (g)
2 NO (g) + O 2
(g) → 2 NO 2
(g) ∆H°/kJ = -114 kJ
2 N 2
(g) + 5 O 2
(g) + 2 H 2
O (l) → 4 HNO 3
(aq) ∆H°/kJ = -255 kJ
N 2
(g) + O 2
(g) → 2 NO (g)
∆H°/kJ = +181 kJ
a) -185 b) -268
c) -313 d) -136
e) -224
9. Given the following equations and ∆H° values, determine the heat of reaction (kJ) at 298 K for the
reaction:
3 NO 2
(g) + H 2
O (l) → 2 HNO 3
(l) + NO (g)
NH 3
(g) + HNO 3
(l) → NH 3
NO 3
(s) ∆H°/kJ = -145.7
NH 4
NO 3
(s) → N 2
O (g) + 2 H 2
O (l) ∆H°/kJ = -125.2
3 NO (g) → N 2
O (g) + NO 2
(g) ∆H°/kJ = -155.8
4 NH 3
(g) + 5 O 2
(g) → 4 NO (g) + 6 H 2
O (l) ∆H°/kJ = -1169.2
NO (g) + 1/2 O 2
(g) → NO 2
(g) ∆H°/kJ = -56.6
a) -300.1 b) -805.9
c) -685.9 d) -70.4
e) -1291.6
10. Which of the following equations represents a reaction that provides the heat of formation of
hydrogen cyanide (HCN)?
a) NH 3
(g) + C (s) → HCN (g) + H 2
(g)
b) CH 4
(g) + N 2
(g) → HCN (g) + NH 3
(g)
c) 1/2 H 2
(g) + C (s) + 1/2 N 2
(g) → HCN (g)
d) CH 3
NH 2
(g) → HCN (g) + 2 H 2
(g)
e) H (g) + C (s) + N (g) → HCN (g)
11. Which of the following equations represents a reaction that provides the heat of formation of
Fe 3
O 4
?
a) 3 FeO (s) + H 2
O (g) → Fe 3
O 4
(s) + H 2
(g)
b) 3 Fe (s) + 4 O (g) → Fe 3
O 4
(s)
c) 3 Fe (s) + 2 O 2
(g) → Fe 3
O 4
(s)
d) FeO (s) + Fe 2
O 3
(s) → Fe 3
O 4
(s)
e) 3/2 Fe 2
O 3
(s) → Fe 3
O 4
(s) + 1/2 O 2
(g)
12. Which of the following equations represents a reaction that provides the heat of formation of
ethanol (CH 3
CH 2
OH)?
a) CH 2
= CH 2
(g) + H 2
O (l) → CH 3
CH 2
OH (l)
b) 2 CO 2
(g) + 6 H 2
(g) → CH 3
CH 2
OH (l) + 3 H 2
O (l)
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PHYSICAL CHEMISTRY
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c) 2 C (s) + 3 H 2
(g) + 1/2O 2
(g) → CH 3
CH 2
OH (l)
d) 2 CO (g) + 3 H 2
(g) → CH 3
CH 2
OH (l) + 1/2O 2
(g)
e) 2 C (s) + 6 H (g) + O (g) → CH 3
CH 2
OH (l)
13. Calculate ∆H° f
(kJ) for the following reaction from the listed standard enthalpies of formation:
PH 3
(g) + 2 O 2
(g) → H 3
PO 4
(s)
∆H° f
PH 3
(g) = +5.4 kJ
∆H° f
H 3
PO 4
(s) = -1279.0 kJ
a) +1284.4 b) -636.8
c) -1284.4 d) -1273.6
e) +1273.6
14. Use the given standard enthalpies of formation to determine the heat of reaction of the heat of
reaction of the following reaction:
N 2
H 4
(l) + O 2
(g) → N 2
(g) + 2 H 2
O (l)
∆H° f
N 2
H 4
(l) = +50.6 kJ/mole
∆H° f
H 2
O (l) = -285.9 kJ/mole
a) -133.5 b) -198.6
c) -622.4 d) -470.6
e) -890.4
15. Calculate ∆H° f
(kJ) for the following reaction from the standard enthalpies of formation ∆H° f
NaCl
(s) = -411.15 kJ.
2 Na (s) + Cl 2
(g) → 2 NaCl (s)
a) +411.15 b) 0.0
c) -822.30 d) +822.30
e) -411.15
16. The standard enthalpy of formation of propane, C 3
H 8
, is -103.6 kJ/mole. Calculate the heat of
combustion of one mole of C 3
H 8
. The heats of formation of CO 2
(g) and H 2
O (l) are -394 kJ/mole
and -285.8 kJ/mole respectively.
a) 2060.0 b) 1721.2
c) -1939.1 d) 2220
e) 1856
17. The standard enthalpy of formation of methanol, CH 3
OH, is -238.6 kJ/mole. Calculate the heat of
combustion of one mole of CH 3
OH. The heats of formation of CO 2
(g) and H 2
O (l) are -394 kJ/
mole and -285.8 kJ/mole respectively.
a) 976 b) 854
c) 1142 d) 727
e) 1300
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PHYSICAL CHEMISTRY
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By: Shailendra Kumar
18. The standard enthalpy of formation of benzene, C 6
H 6
, is +49.2 kJ/mole. Calculate the heat of
combustion of one mole of C 6
H 6
. The heats of formation of CO 2
(g) and H 2
O (l) are -394 kJ/mole
and -285.8 kJ/mole respectively.
a) 3420 b) 2150
c) 2860 d) 3270
e) 3560
19. Using the following information calculate the heat of formation of NF 3
.
NH 3
(g) + 3 F 2
(g) → NF 3
(g) + 2 HF(g)
∆H° = -604.8 kJ
∆H° f
NH 3
(g) = -46.19 kJ/mole
∆H° f
HF(g) = -269 kJ/mole
a) -140 b) -97.2
c) -113 d) -165
e) -198
20. The heat of formation of PCl 3
(g) is -287.0 kJ/mole. What is the heat of reaction for the following
process?
2 PCl 3
(g) → 2 P(s) + 3 Cl 2
(g)
a) +306.4 b) -612.8
c) +153.2 d) -306.4
21. Using the following information calculate the heat of formation of HCl.
2 Cl 2
(g) + 2 H 2
O (l) → 4 HCl (g) + O 2
(g)
∆H° = +202.5 kJ ∆H° f
H 2
O (l) = -285.85 kJmole
a) +122.5 b) -193.5
c) -92.3 d) +92.3
e) -122.5
22. The heats of formation of CO 2
(g) and H 2
O (l) are -394 kJ/mole and -285.8 kJ/mole respectively.
Using the data for the following combustion reaction, calculate the heat of formation of C 6
H 6
(l).
2 C 6
H 6
(l) + 15 O 2
(g) → 12 CO 2
(g) + 6 H 2
O (l)
∆H° = -6541.1 kJ
a) -49.2 b) 49.2
c) 20.2 d) 61.2
e) -61.2
23. The heats of formation of CO 2
(g) and H 2
O (l) are -394 kJ/mole and -285.8 kJ/mole respectively.
Using the data for the following combustion reaction, calculate the heat of formation of C 3
H 4
(g).
C 3
H 4
(g) + 4 O 2
(g) → 3 CO 2
(g) + 2 H 2
O (l)
∆H° = -1939.1 kJ
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PHYSICAL CHEMISTRY
By: Shailendra Kumar
a) 212.2 b) 185.4
c) -103.8 d) 20.4
e) -143.3
24. The heats of formation of CO 2
(g) and H 2
O (l) are -394 kJ/mole and -285.8 kJ/mole respectively.
Using the data for the following combustion reaction, calculate the heat of formation of C 2
H 2
(g).
2 C 2
H 2
(l) + 5 O 2
(g) → 4 CO 2
(g) + 2 H 2
O (l)
∆H° = -2601 kJ
a) -226.7 b) 226.7
c) -238.6 d) 253.2
e) 238.7
25. The combustion of 1.00 mol of the amino acid alanine, C 3
H 7
O 2
N, liberates 1622 kJ of heat. What
quantity of heat (kJ) is liberated by 37.2 g of alanine?
(Atomic weights: C = 12.01, O = 16.00, N = 14.01, H = 1.008).
a) 677 b) 702
c) 767 d) 733
e) 635
26. Calculate the heat absorbed (kJ) for the reaction in which 1.0 g of ICI is formed.
(Atomic weights: I = 126.9, Cl = 35.45).
I 2
(s) + Cl 2
(g) → 2 ICl (g)
∆H°= 36 kJ
a) 0.11 b) 0.44
c) 2.2 d) 1.1
e) 0.22
27. Aluminum reacts with chromium (III) oxide according to the following equation. How much heat
(kJ) is released by the reaction of excess aluminum with 25.0 g of Cr 2
O 3
?
(Atomic weights: Cr = 52.00, Al = 26.98, O = 16.00).
2 Al (s) + Cr 2
O 3
(s) → Al 2
O 3
(s) + 2 Cr (s)
∆H°= -536 kJ
a) 88.2 b) 44.1
c) 112.0 d) 98.4
e) 64.5
28. The fat, glyceryl trioleate, is metabolized via the following reaction. Given the enthalpies of formation,
calculate the energy (kJ) liberated when 1.00 g of this fat reacts. (At Wt. C=12.01,H=1.008,O=16)
C 57
H 107
O 6
(s) + 80 O 2
(g) → 57 CO 2
(g) + 52 H 2
O (l)
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∆H° C 57
H 107
O 6
(s) = -70870 kJ/mole
∆H° H 2
O (l) = -285.8 kJ/mole
∆H° CO 2
(g) = -393.5 kJ/mole
a) 33.4 b) 30.2
c) 40.4 d) 37.8
e) 42.6
29. Dimethylhydrazine, used as a rocket fuel. Given the enthalpies of formation, calculate the energy
liberated when 10 g of dimethylhydrazine reacts.
(Atomic weights: C = 12.01, N = 14.01, H = 1.008, O = 16.00).
(CH 3
) 2
NNH 2
(l) + 4 O 2
(g) → 2 CO 2
(g) + 4 H 2
O (g) + N 2
(g)
∆H° (CH 3
) 2
NNH 2
= +42.0 kJ/mole
∆H° H 2
O (g) = -241.8 kJ/mole
∆H° CO 2
(g)= -393.3 kJ/mole
a) -1795.8 b) -1642.6
c) -1828.6 d) 3.0 x 10 2
e) -1892.5
30. Nitroglycerin decomposes via the following process. Given the enthalpies of formation, calculate
the energy liberated when 10 g of nitroglycerin is detonated.
(Atomic weights: C = 12.01, H = 1.008, N = 14.01, O = 16.00).
4 C 3
H 5
(NO 3
) 3
(l) → 6 N 2
(g) + O 2
(g) + 12 CO 2
(g) + 5 H 2
O (g)
∆H° C 3
H 5
(NO 3
) 3
(l) = -364 kJ/mole
∆H° CO 2
(g) = -393.5 kJ/mole
∆H° H 2
O(g) = -241.8 kJ/mole
a) -4825 b) 196
c) -3383 d) 49
e) -4475
31. Calculate the ∆H° for the following reaction using the given bond energies. (H - N = 389 kJ; O - O
= 494 kJ; H - O = 463, N - N = 941).
4 NH 3
(g) + 3 O 2
(g) → 6 H 2
O (g) + 2 N 2
(g)
a) -1132 b) -1220
c) -1288 d) -1330
e) -1180
32. Use the following bond energies to calculate ∆H° for the given reaction. ( H - C = 414; H - O = 464;
C = O = 730; H - H = 435,: C - O = 351).
CH 2
= O (g) + H 2
(g) → CH - OH (g)
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a) -44 b) -76
c) -64 d) -52
e) -88
33. Using the following bond energies and the heat of reaction for the reaction, calculate the average
bond energy of Xe - F in XeF 2
. ( H - H = 435; H - F = 565).
XeF 2
(g) + H 2
(g) → 2 HF (g) + Xe (g)
∆H° = -430 kJ
a) 352 b) 264
c) 133 d) 172
e) 298
34. A sample of 25.00 mL of HCl (aq) was mixed with 25.00 mL of KOH (aq) of the same concentration
in a calorimeter. As a result, the temperature rose from 25.00 to 26.60°C. Given that ∆H° = -56.02
kJ for the reaction and that the heat capacity of dilute aqueous solutions is 75.4 J/°K mol, determine
the molarity of the original HCl solution. (Assume the heat capacity of the calorimeter to be
negligible.).
H 3
O + (aq) + OH – (aq) → 2 H 2
O (l)
a) 0.24 b) 0.012
c) 0.0060 d) 0.48
e) 0.024
35. A 5.00 g sample of CS 2
was burned in excess O 2
in a calorimeter. The calorimeter contained 750
g of H 2
O and has a heat capacity of 1.47 kJ/°C. The temperature of the calorimeter and its
contents increased form 18.00°C to 33.33°C. What quantity of heat (kJ) would be liberated by the
combustion of one mole of CS 2
? (Atomic weights : C = 12.01, O = 16.00, S = 32.06).
a) 1.07 x 10 3 b) 1.21 x 10 3
c) 7.25 x 10 2 d) 9.02 x 10 2
e) 8.15 x 10 2
36. When 2.500 g of sulfur were burned completely in oxygen to SO 2
(g), the temperature of 1.0 kg of
water in a bomb caloimeter of negligible heat capacity was raised from 22.00°C to 27.40°C.
Calculate ∆H° (kJ) for the reaction per mole of SO 2
formed.
(Atomic weights: S = 32.01, O = 16.00)
a) -290 b) -310
c) -300 d) -330
e) -320
37. A 500.0 g sample of lead is heated and then is placed into an insulated vessel containing 1.00 L of
water at 20.0°C. The final temperature after equilibrium is achieved is 23.5°C. What was the
temperature ( 0 K) of the lead? The heat capacity of lead is 0.130 J/g°C.
a) 221.2 b) 234.2
c) 204.4 d) 248.8
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PHYSICAL CHEMISTRY
By: Shailendra Kumar
A N S W E R S
1. b 16. d 31. c
2. b 17. d 32. c
3. b 18. d 33. c
4. b 19. c 34. a
5. b 20. c 35. a
6. b 21. c 36. a
7. d 22. b 37. d
8. d 23. b
9. d 24. b
10. c 25. a
11. c 26. a
12. c 27. a
13. c 28. d
14. c 29. d
15. c 30. d
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