Acidic

When we take some reaction either sulphur dioxide (SO2) or carbon dioxide (CO2)
is produced , we can put a moist pH paper near the place where collect the gas ,
If the paper turn red or orange , This prove that the gas produce is acidic

OR put a blue limus paper near the place where the gas produce , turn red mean the gas is acidic

P.S when Sulphur dioxide produce is test with a blue litmus paper , the paper will turn
red and become colourless because sullphur dioxide is a bleaching agent

Let the gas pass through water, they will disolve in water slightly. Test the water, it will show acidic.