Thermodynamics / Quantum Mechanics, Chemistry

1. A laboratory animal exercised on a treadmill that was connected to a weight with a mass of
250. g through a pulley. The work done by the animal raised the weight through 1.32 m. At the
same time the animal gave off 8.0 J of energy as heat. Disregarding any other losses and treating
the animal as a closed system, what was the change in internal energy of the animal?

2. A piece of metal of mass 20.0 g at 100.0 oC is placed in a calorimeter containing 50.7 g at water
at 22.0 oC. The final temperature of the mixture is 25.7 oC. What is the specific heat capacity of
the metal?

3. Suppose that coal of density 1.5 g.cm-3 is carbon. The combustion of carbon is described by the
equation
C(s) + O2(g) ---> CO2(g) ?Ho = -394 kJ
(a) Calculate the heat produced when a lump of coal of size 7.0 cm x 6.0 cm x 5.0 cm is burned.
(b) Estimate the mass of water that can be heated from 25 oC to 100.oC by burning this piece of
coal.

4. Calculate the standard enthalpy of formation for dinitrogen pentoxide from the following data
and from the standard enthalpy of formation of nitric oxide.

2NO(g) + O2(g) ---> 2NO2(g) ?Ho = -114.1 kJ

4NO2(g) + O2(g) ---> 2N2O5(g) ?Ho = -110.2 kJ

5. The average speed of a helium atom at 25oC is 1.23 x 103 m.s-1. What is the average wavelength
of a helium atom at this temperature?

6. Complete the following questions for the hydrogen atom:

(a) What is the highest energy photon that can be absorbed by a ground-state hydrogen atom
without causing ionization?
(b) What is the wavelength of this radiation?
(c) To what region of the electromagnetic spectrum does this photon belong?

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