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 given potassium chloride and oxygen.
`2KCl O_(3) to 2KCl+3O_(2)`
3 moles of `O_(2)-="2 moles of "KCl`
`(3 xx 22.4)"L of O"_(2) at STP=(2 xx 74.5)` grams of KCl
The weight of residue (KCl) obtained when 3.36L of `O_(2)` is collected at STP= `(3.36)/(3 xx 22.4) xx 2 xx 74.5 =7.45"grams"`