Certain mass of potassium chlorate is thermally decomposed and 3.36 L of `O_(2)` is collected at STP. What will be the weight of the residue in the experiment? 

Explanation

Potassium chlorate on decomposition gives potassium chloride and oxygen
`2KCIO_(3)rarr2KCI+3O_(2)`
3 moles of `O_(2)` = 2 moles of KCI
`(3xx22.4)L "of" O_(2)` at STP = ` (2xx74.5)` grams of KCI
The weight of residue (KCI) obtained when 3.36 L of `O_(2)` is collected at STP `=(3.36)/(3xx22.4)xx2xx74.5`
=7.45 grams