When 50 gm of a sample of sulphur was burnt in air 4% of the sample was left over. Calculate the volume of air required at STP containing 21% oxygen by volume.

Explanation

Given that when a 50 gms of sample of sulphur was burnt 4 % of the sample was left over.
`:. 50 " gms of"" S"to 48 ` gms of .S. burnt.
Chemical equation is S + `O_(2) to SO_(2)`
32 gm of .S. 22.4 lit of `O_(2)` at STP
48 gms of S `to`
`(48 x 22.4)/(32)=33.6` lit
100 ml air contains 21 ml of oxygen
100 lit of air contains 21 lit of oxygen
33.6 lit of Oxygen is present in `(33.6 x 100)/(2.1)=160` lit
`:.` The volume of air needed for combustion =160 lit