Transcript Chem 1310: Introduction to physical chemistry Part 1a: PSP chapter 6

Chem 1310:
Introduction to physical chemistry
Part 1a: PSP chapter 6
Peter H.M. Budzelaar
PSP 6.1, p217
(a) One hot dog is 160 Cal. How much in joules?
(b) 1 Watt of power is 1 J/s; an x-Watt device
running for y seconds uses x*y joules. How much
electrical energy (in joules) is use by a 75-watt
bulb burning for 3 hours?
(c) One packet of sweetener provides 16 kJ of
nutritional energy. How much is this in kcal?
PSP 6.2, p222
The internal energy of a mixture of hydrogen and
oxygen decreases by 2400 J when it burns. The
surroundings are heated by 1.89 kJ. How much
work is done by the system on the surroundings?
PSP 6.3, p225
250 g of Al is heated using 24.1 kJ of energy. The
initial temperature is 5.0°C; what is the final
temperature?
(specific heat of Al: 0.902 J g-1 K-1, from Table 6.1)
PSP 6.4, p227
A filled coffee cup (250 mL) is heated from 37°C to
65°C, no work being done. What is DEsystem?
PSP 6.5, p228
400 g Fe is heated in a flame, then immersed in
1000g water of 20.0°C. The final temperature is
32.8°C; what was the temperature of the Fe before
cooling?
(specific heat of Fe: 0.451 J g-1 K-1, from Table 6.1)
PSP 6.6, p233
For K melting at 1 atm, the heat transfer is 14.6
cal/g. At the melting point, the densities of solid
and liquid K are 0.86 and 0.82 g/ml, respectively.
A volume change of 1 mL at 1 atm corresponds to
0.10 J of work. Calculate DH and DE for melting
1.00 g of K.
PSP 6.7, p235
Sublimation of 1 mol of iodine at 25°C and 1 bar has
DH = +62.4 kJ.
(a) How much energy must be transferred to
vaporize 10.0 g of solid iodine.
(b) How much energy is transferred if 3.42 g
iodine vapour condenses to solid.
(c) Is the change under (b) exothermic or
endothermic?
PSP 6.8, p238
Ca(s) + ½ O2 (g) CaO(s) DH° = -635.09 kJ
Write the equation and calculate the enthalpy change
for forming 4 moles of O2 (g) from CaO.
PSP 6.9, p240
Given the equation
H2O(l) H2 (g) + ½ O2 (g) DH° = +285.8 kJ
how much thermal energy is required to maintain
constant temperature when decomposing 12.6 g
liquid water to H2 and O2 at 25°C?
PSP 6.10, p244
1 Fritos chip (1.0 g) is placed in a bomb calorimeter
(heat capacity 877 J/K) containing 832 g of water.
Burning (with excess oxygen) results in a
temperature change from 20.64 to 25.43°C.
Check that this agrees with the statement that the
chip provides 5 Cal of energy when metabolized.
PSP 6.11, p245
100 mL 1M HCl and 100 mL 1M NaOH, both at
20.4°C, are combined in a coffee cup calorimeter.
Given the neutralization equation
H +(aq) +OH-(aq)  H2O(l) DH° = -58.7 kJ
calculate the final temperature.
PSP 6.12, p248
Given the equations
C(s) + O2 (g) CO2 (g)
CO(g) + ½ O2 (g) CO2 (g)
Calculate DH° for:
C(s) + ½ O2 (g) CO (g)
DH° = -393.5 kJ
DH° = -283.0 kJ
PSP 6.13, p 249
Write thermochemical equations for:
(a) Standard molar enthalpy of formation of
NH3(g) at 25°C is -46.11 kJ/mol
(b) Standard molar enthalpy of formation of CO(g)
at 25°C is -110.525 kJ/mol
PSP 6.14, p252
Nitroglycerin, DHf° = -364 kJ/mol, decomposes
explosively according to
2 C3H5(NO3)3 (l)  3 N2 (g) + ½ O2 (g) + 6 CO2 (g) + 5 H2O (g)
Calculate the energy transfer when 10.0 g
nitroglycerin explodes.
PSP 6.15, p253
Using Table 6.2, calculate the molar heat of
combustion of SO2 (g) to SO3 (g).
PSP 6.16, p258
For whole milk (5.0% carbohydrate, 4.0% fat, 3.3%
protein by wt):
(a) estimate the caloric value of an 8-oz (227-g) glass
(b) how long would this glass support a 70-kg male
taking a leisurely walk?
Work and Volume
A volume change requires work: w = p DV
when expressed in the correct units!
We need both in SI units:
p in Pascal: 1 atm = 101.325 kPa = 101325 kg m-1 s-2
DV in m3: 1 L = 1 dm3 = 10-3 m3
then w = p DV in (kg m-1 s-2)(m3) = kg m2 s-2 = J
Review Question 33
400 g Fe is heated in a flame, then immersed in
1000g water of 20.0°C. The final temperature is
32.8°C; what was the temperature of the Fe before
cooling?
(specific heat of Fe: 0.451 J g-1 K-1, from Table 6.1)
Review Question 39
200 g Al is heated in a flame, then immersed in
500 mL water of 22.0°C. The final temperature is
33.6°C; what was the temperature of the Al before
cooling?
(specific heat of Al: 0.902 J g-1 K-1, from Table 6.1;
density of water at 22.0°C: 0.98 g/cm3)
(the answer on p A.85 is wrong)
Review Question 40
200 g Cu is heated in a flame to 500°C, then
immersed in 1000g water of 23.4°C. What is the
final temperature?
(specific heat of Cu: 0.385 J g-1 K-1, from Table 6.1)
Review Question 87
Given:
PbO(s) + C(s)  Pb(s) + CO(g)
2 C(s) + O2 (g)  2 CO(g)
asked:
Pb(s) + ½ O2 (g)  PbO(s)
Endothermic or exothermic?
DH° = 106.8 kJ
DH° = -221.0 kJ
DH° = ???
(1)
(2)
Review Question 94
6 CO2 + 6 H2O  6 O2 + C6H12O6
From Table 6.2,
DHf°(CO2 (g)) = -285.830 kJ/mol
DHf°(H2O(l)) = -393.509 kJ/mol
DHf°(C6H12O6 (s)) = -1274.4 kJ/mol
DH° = ???