1. The specific heat capacity of aluminum is 0.900 J/g·K. What quantity of heat is

required to heat 5.60 kg of aluminum from 20.0 °C to 358.7 °C?

2. The initial temperature of a 215-g sample of graphite (c = 0.720 J/g·K) is -82.1 °C. If

the sample absorbs 15.2 kJ of heat, what is its final temperature?

3. What is the mass of a sample of water (c = 4.184 J/g·K) that loses 340 J of heat

energy in cooling from 50.0 °C to 20.0 °C?

4. A 26.47-g piece of lead, initially at 89.98 °C, is dropped into 100. g of water at

22.50 °C. When the system reaches equilibrium, the temperature is 23.17 °C. What

is the specific heat capacity of lead?

5. A piece of gold (c = 0.129 J/g·K) with a mass of 14.7 g is heated in boiling water to

99.5 °C and then dropped into a calorimeter containing 30.0 g of water at 19.6 °C.

What equilibrium temperature will the system reach?

6. Using the information in Appendix IIB, calculate °

Δrxn

H for each of these reactions:

a. CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l)

b. 2 CO(g) + O2(g) → 2 CO2(g)

c. 2 Al(s) + Fe2O3(s) → 2 Fe(s) + Al2O3(s)

d. 3 N2H4(l) → 4 NH3(g) + N2(g)

7. Use your answers to question 6 to calculate the heat changes for the following:

a. the combustion of 5.00 g of methane, CH4

b. the decomposition of 31.2 g of carbon dioxide (from reaction 6b)

c. the complete reaction of 4.60 kg of aluminum

d. the formation of 91.7 g of hydrazine, N2H4

Answers: 1) 1.71 MJ 2) 289.3 K or 16.1 °C 3) 2.71 g 4) 0.158 J/g·K 5) 20.8 °C

6) a) -890.4 kJ/mol b) -566.0 kJ/mol c) -850.2 kJ/mol d) -335.5 kJ/mol

7) a) -277.5 kJ b) 201 kJ c) -72500 kJ d) 330.4 kJ

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Address:
Biology and Chemistry

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Chemistry

Upload date:
23/12/2012