Best Answer - Chosen by Voters
1 S + 1 O2 -> 1 SO2
So 1 mole (or 6.02 x 10 to the 23 units) of sulfur needs 1 mole of of O2 to make one mole of SO2.
Another example would be:
2C2H6 + 7O2 -> 4CO2 + 6H2O
One mole of ethane (C2H6) would produce 3 moles of H2O since the ratio between the two compounds coefficients in the balanced reaction is 2:6 which simplifies to 1:3.
Steps to do that are:
1. Write the chemical expression.
2. Balance it.
3. Use the coefficient of the compound you're starting with to make a ratio.
4. Convert to moles with the substance you have some amount and then using the ratio get the other (ex: if you have 2 moles of a reactant and the ratio between it and a product's coefficients in a reaction is 2:3 then there would 3 moles of product made).