Yield reaction

Jan 2020
First of all, I apologize if wrote something incorrectly because English is not my first language.
67.2 liters of sulfur (IV) oxide were obtained with a reaction yield of 80%. How many grams of sulfur is burned?
So given info is V (SO2) actual = 67,2 l ir η (SO2) = 80 % and find m (SO2) theoretical.
I know the formula η= (V actual : V theoretical) * 100%), but how I should get grams?
Apr 2015
I assume the burning takes place in the atmosphere so the products will return to STP (standard temperature and pressure) before measurement.

So can you use the gas laws to work out the number of moles of sulphur dioxide occupying 67.2 litres at STP ?

Since this is a Chemistry question you can then work out the mass of sulphur that is 80% of the original, from the number of moles and the molecular weight.

Finding the original mass is then a simple question of proportional scaling.