Question

Roasting galena [lead(II) sulfide] is an early step in the industrial isolation of lead. How many liters of sulfur dioxide, measured at STP, are produced by the reaction of 4.77 kg of galena with 125 L of oxygen gas at 220°C and 2.00 atm? Lead(II) oxide also forms.

Answer 1

2 PbS + 3O₂ ------> 2 PbO + 2SO₂

from to idealgas equation

PV =nRT

2.00 x 125 = n x 0.0821 x 493

n = 6.177

moles of O2 = 6.177 mol

molesof PbS taken = 4.77 x 10³ g / 239.266 g /mol

                              = 19.94 moles

from the balanced equation :

2 PbS + 3O₂ ------> 2 PbO + 2SO₂

    2          3

19.94   6.177

here limiting reagent is O2.

3 mol O2   ------------> 2 mol SO2

6.177 mol O2   ---------> ??

moles of SO2 = 6.177 x 2 / 3 = 4.118

At STP :

1 mol SO2   -----------> 22.4 L

4.118 mol SO2 -----------> ??

volume of SO2 = 4.118 x 22.4 = 92.24

volume of SO2 = 92.2 L