Posted by CJ on .
Sulfuric acid (H2SO4) is prepared commercially from elemental sulfur using the contact process. In a typical sequence of reactions, the sulfur is ﬁrst burned:
S + O2 → SO2 ,
then it is converted to SO3 using a catalyst:
2 SO2 + O2 → 2 SO3 .
The resulting SO3 is reacted with water to produce the desired product:
SO3 + H2O → H2SO4 .
How much sulfuric acid could be prepared
from 34 moles of sulfur?
Answer in units of g

AP Chemistry 
DrBob222,
This is a regular stoichiometry problem. You can work it as three problems OR you can collapse the three into one problem with a shortcut.
Method 1: Three problems.
S + O2 ==> SO2. 34 mol S; calculate mols SO2 formed. Then
2SO2 + O2 ==> 2SO3. Use mols SO2 from the first problem and calculate mols SO3 formed.
SO3 + H2O ==> H2SO4. Use mols SO3 from second problem and calculate mols H2SO4 formed.
Method 2:
Write all of the equations.
S + O2 > SO2
2SO2 + O2 ==> 2SO3
SO3 + H2SO4 = H2SO4.
Now watch this. Using the coefficients in the balanced equation we have
1 mol S = 1 mol SO2
2 mol SO2 = 2 mol SO3 or 1>1
1 mol SO3 = 1 mol H2SO4
Therefore we can see that 1 mol S forms 1 mol H2SO4 and it seems obvious then that 34 mols S will produce 34 mols H2SO4. 
AP Chemistry 
CJ,
So that would also equal 34 grams right?

AP Chemistry 
DrBob222,
No. The problem asked for mols and answer is 34 mols S. A mol of S has a mass of 32.066 grams; therefore, 34 mols will be 34 x 32.066 = a bunch of grams.