A typical coal-fired electric generating plant will burn about 3 metric tons of

Question

A typical coal-fired electric generating plant will burn about 3 metric tons of coal per hour.

Most of the coal burned in the United States contains 1 to 4 % by weight sulfur in the form of pyrite, which is oxidized as the coal burns:

Once in the atmosphere, the SO2 is oxidized to SO3, which then reacts with water in the atmosphere to form sulfuric acid:

If 57.1 metric tons of coal that contains 3.43 % by weight S is burned and all of the sulfuric acid that is formed rains down into a pond of dimensions 306 m x 273 m x 3.45 m, what is the pH of the pond? (OK to assume 2 mol H3O+ per mole H2SO4.)

Hint: 1 metric ton = 1000 kg

Explanation / Answer

4FeS2(s) + 11 O2(g) ->  2 Fe2O3(s) + 8 SO2(g)

SO2 + 1/2O2 = SO3

SO3(g) + H2O(l) --> H2SO4(aq)

m = 57.1 tons of coal

mass of S =3.43/100*57.1 = 1.95853 ton of S

tonmol of S= mass/MW = 1.95853 /32 = 0.06120 ton mol of S

0.06120 ton mol of S = 0.06120 ton mol of SO2 = 0.06120 tonmol o fSO3

then..

0.06120 ton mol of OS3 = 0.06120 ton mol of H2SO4

gmol of H2SO4 = ton mol * 10^6

V = 206*273*3.45 =194021.1m3 = 194021.1*10^3 L

[H2SO4] = (0.06120*10^6 ) / (194021.1*10^3) = 0.0003154

assume

[H+] = 2*[H2SO4] = 0.0003154*2 = 0.0006308 M

pH = -log(H+) = -log(0.0006308 = 3.2

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