[Savan]

1. The amount of sulfur emitted into the atmosphere in a year by burning coal is 75 million tonnes. Assuming that the entire quantity of sulfur is solid state, how much volume will occupy sulfur (sulfur attributed to a quantity of a building)? (Density S = 2 g / cm3).

2. SO2 and SO3 is released into the environment from various industrial activities. Considering that these two oxides of sulfur are the only source of pollution as a result of industrial activities, was collected a stample of 20 liters air in normal conditions. It was bubbled through 100 mL H2O2 concentration c = 2.4 * 10-3 mol / L. After completion of bubbling, the solution was treated with BaCl2, resulting 105.6 mg precipitat.The excess of H2O2 is titrated with a solution containing 15.9 mg K2Cr2O7. Determine the concentrations expressed in g oxide / m3 air for that two oxides present in the air : SO2 and SO3.

[Hunter2]

What is your attempt?

[Savan]

For problem no. 2 I used equivalence law:...But I don't know to solve the problem from chemical reactions.
E K2Cr2O7 = M/6 = 294/6 = 49
15,9 mg K2Cr2O7 = 15,9 * 10-3 g K2Cr2O7 => E K2Cr2O7 =M/49 = 15,9 * 10-3 / 49 = 3,24 * 10-4 ( equivalent K2Cr2O7) => 
->   3,24 * 10-4 equivalent H202 =>      2* 2,4 * 10-4  equiv. H2O2 = 4,8 * 10-4  E H2O2 =>
2,4 * 10-4 mol H2O2                           
E H2O2 = M/2
->   4,8-3,24 = 1,56 * 10-4 E H2O2 => 1,56 * 10-4 E SO2 => 2 * 1,56 = 3,2 * 10-4 mol SO2
M SO2= 3,2 * 10-4 * 64g = 0,12 g SO2
E SO2 = M/2

M BaSO4=233 g/mol, 105,6 mg BaSO4 =105,6 * 10-3 g BaSO4 ->4,5 * 10-4 mol -> 3,2 * 10-4 mol SO2 and 1,3 * 10-4 mol SO3

M SO3 = 80 g/mol
m SO3 = 1,3 * 10-4 * 80 = 0,104 g.

20L air ..0,12g SO2....0,104g SO3
1000L air (1m3)..x g....y g

x=200/20 = 10 g SO2 m3 ... and y=5,2g SO3 m3

[Borek]

For problem no. 2 I used equivalence law:...But I don't know to solve the problem from chemical reactions.

Not looking at what you did: equivalents are just a conclusion of the reaction equations, so both approaches are (if correctly used) perfectly equivalent.

In general: start writing reaction equations. If you know what equivalents are here, you know what the reactions are, aren't you?

[Savan]

I know that chemical reactions, but it is harder solving through chemical reactions.

" SO2 + 1/2O2 = SO3
  SO2 + H2O2 = H2SO3 + 1/2O2
  SO3 + H2O2 = H2SO4 + 1/2O2
  H2SO4 + BaCl2 = BaSO4 + 2HCl "

[AWK]

These are not correct reactions:

SO2 + H2O2 = H2SO3 + 1/2O2
  SO3 + H2O2 = H2SO4 + 1/2O2

[Savan]

These are not correct reactions:

SO2 + H2O2 = H2SO3 + 1/2O2
  SO3 + H2O2 = H2SO4 + 1/2O2

Right! "SO2 + H2O2 = H2SO4
          SO3 + H2O2 = I'm not sure..

[Hunter2]

The main reaction is the first one. The SO₃ you dont have to oxidise, because its not possible. It has only dissolved in water. in both cases you get sulfuric acid. This will get the precipitate of Bariumsulfate.  This value reflects to the whole SO₃.

You need the reaction of bichromate with Peroxide. The value you get from Bichromate has to be substracted and you can calculate SO₂ as well.

[Savan]

Thank you very much!!