What number of moles of O2(g) is required to react with 3.6 mol SO2(g) in the following reaction?
2SO2(g)+ O2(g) → →2SO3(g)

first balance the equation:

2SO2+O2=2SO3. BALANCED EQUATION

find the ratio:

2:1:2. SO2:O2:SO3

5.0 moles of SO2 React

1/2×5.0 moles=2.5moles of O2 are needed

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.