Coal-fired electric power plants are a major source of atmospheric SO_2, a pollu

Question

Coal-fired electric power plants are a major source of atmospheric SO_2, a pollutant that causes acid rain, harms plants, and aggravates human respiratory disease. Sulfur appears as an impurity in coal, generally as less than 4% of the total mass. a. Write the balanced chemical reaction for the combustion of sulfur ("S") with oxygen gas (O_2), and calculate the mass of SO_2 (in kg) produced from burning 1 metric ton of coal containing 1.2% sulfur by mass. b. Using your answer to #2a and the table in #1, calculate the mass of SO_2 released per kWh generated by this coal.

Explanation / Answer

At normal atmospheric conditions Sulphur is mildly flammable, The products formed by the combustion of sulphur are sulfur dioxide and sulfur trioxide.

S(s) + O2(g) ——> SO2(g)

2S(s) + 3O2(g) ——> 2SO3(g)

SO2 and SO3 are the major source of acid rain as they combine with atmospheric moisture to form sulphurous and sulphuric acid respectively:

SO2(g) + H2O(g) ——> H2SO3(g), SO3(g) + H2O(g) ——> H2SO4(g)

We have 1 metric ton i.e 1000 kg of coal which contains 1.2% sulphur:

i.e 100 kg contain 1.2 kg Sulphur

so 1000 kg will contain= (1.2/100)*1000
Mass of sulphur = = 12kg of Sulphur
The combustion equation forming sulphur dioxide is as follows:
S+O2 SO2
i.e 1mol S reacts with 1 mol O2 to produce 1 mol SO2
Molar mass SO2 = 64g/mol
Molar mass S = 32 g/mol
The molar mass of SO2 is double that of S.
Therefore 12kg of S will produce 24 kg SO2

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