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 Esystem?

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 H and E for melting 1.00 g of K.

PSP 6.7, p235

Sublimation of 1 mol of iodine at 25°C and 1 bar has H = +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) H° = -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) H° = +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) H° = -58.7 kJ

calculate the final temperature.

PSP 6.12, p248

Given the equations

C(s) + O2 (g) CO2 (g) H° = -393.5 kJ

CO(g) + ½ O2 (g) CO2 (g) H° = -283.0 kJ

Calculate H° for:

C(s) + ½ O2 (g) CO (g)

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, Hf° = -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 Vwhen 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

V in m3: 1 L = 1 dm3 = 10-3 m3

then w = p V 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 in500 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) H° = 106.8 kJ (1)

2 C(s) + O2 (g) 2 CO(g) H° = -221.0 kJ(2)

asked:

Pb(s) + ½ O2 (g) PbO(s) H° = ???

Endothermic or exothermic?

Review Question 94

6 CO2 + 6 H2O 6 O2 + C6H12O6 H° = ???

From Table 6.2,

Hf°(CO2 (g)) = -285.830 kJ/mol

Hf°(H2O(l)) = -393.509 kJ/mol

Hf°(C6H12O6 (s)) = -1274.4 kJ/mol