A typical frostless refrigerator uses 655 k W h of energy per year in the form o

Question

A typical frostless refrigerator uses 655 kWh of energy per year in the form of electricity. Suppose that all of this electricity is generated at a power plant that burns coal containing 3.5% sulfur by mass and that all of the sulfur is emitted as SO2 when the coal is burned.

If all of the SO2 goes on to react with rainwater to form H2SO4, what mass of H2SO4 is produced by the annual operation of the refrigerator? (Hint: Assume that the remaining percentage of the coal is carbon and begin by calculating ?H?rxn for the combustion of carbon.)         

Explanation / Answer

SO2 + O + H2O ? H2SO4

1 mole of SO2 makes 1 mole of H2SO4.

Coal is primarily carbon in solid state and the heating value of coal is 32,800 kJ/kg. The refrigerator uses 655kWh of energy. Converting this to kJ you get 1638000 kJ of energy used by the refrigerator over the course of 1 year. Assuming that all of the energy released by burning the coal is used to create electricity, to create this much energy, you will need to burn 1638000 kJ/[32800 kJ/kg] = 50 kg of coal.

You are given that 3.5% of the coal mass is Sulfur. Therefore, 1.75 kg of sulfur is found in 50 kg of coal. This is .0547 kmol of S which produces .0547 kmol of SO2

Since 1 kmol of SO2 produces 1 kmol H2SO4, 0.0547 kmol of H2SO4 is produced, which is 3.5 kg. (mol weight of H2SO4 is 98.08 kg/kmol)

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