Problem Set 1 (Due at beginning of class on assigned date):

1. Tungsten has been used as a lamp filament since the early 1900s.� Incandescent lights operate by passing an electric current through a tungsten filament; electrical resistance results in heating of the tungsten filament to a temperature of approximately 2900�C.� Approximately 90% of the energy expended in incandescent light bulbs is used to generate heat; the rest produces light.

a. Calculate the wavelength at which the intensity of light emitted from this light bulb is at a maximum.

b. Sketch a diagram of wavelength vs intensity illustrating the types and relative amounts of light emitted.

c. The thermodynamic efficiency of coal-fired power plants in the Charlotte region ranges from 25% to 42%.� This efficiency is primarily a limitation of the second law of thermodynamics and represents the percentage of heat generated by the coal combustion chemical reaction that is actually converted into electricity.� Transmission of electricity across the grid also results in energy losses of 5-10% of the generated electricity.� Calculate the overall percentage of heat energy produced from burning coal that is actually converted to light generated by incandescent lights plugged into the grid.� Clearly show your rationale, all calculations, and all assumptions.

2. Later in the course, we will examine the generation of tropospheric ozone on hot summer days.� One of the steps in this process involves the photodecomposition of nitrogen dioxide (NO₂) to produce nitrogen monoxide (NO) and an oxygen atom.� The brown tint of air in polluted cities is primarily due to NO₂ absorption of visible light.���

a. Calculate the change in enthalpy for this reaction using the enthalpies of formation table (for NO and NO₂) from your Atkins text.� The enthalpy of formation for atomic oxygen is 248 kJ/mole (half the bond enthalpy for O₂).

b. Determine the range of wavelengths (in nm) of light with sufficient energy to photodecompose nitrogen dioxide.

c. Comment on your answer to b in terms of light present at ground level.

3. Baird 1.7

4. Baird 1.9, also draw clearly labeled enthalpy-reaction coordinate diagrams for each of the two reactions.