Gas Stoichiometry Problems

Graham's Law

Example 4:
Hydrogen sulfide reacts with sulfur dioxide to give H₂O and S, H₂S + SO₂ = H₂O + S(solid), unbalanced.If 6.0 L of H₂S gas at 750 torr produced 3.2 g of sulfur, calculate the temperature in C. Solution
Balanced reaction:

2 H2S + SO2 = 2 H2O + 3 S(solid),
 2 mol                3*32 = 96 g

         2 mol H2S
 3.2 g S ---------- = 0.067 mol H2S;
          96 g S

  P = 750/760 = 0.987 atm

      PV            0.987 atm * 6 L 
  T = --- = --------------------------------
      n R   0.067 mol * 0.08205 atm L /(mol K)

    = 1085 K
    = 812°C

Discussion:
Atomic mass: H, 1.0; O, 16.0; S, 32.0. R = 0.08205 L atm /(K mol) is OK but watch units used for pressure. source: http://www.science.uwaterloo.ca/~cchieh/cact/c120/gastoichiometry.html