A student forgot to add the reaction mixture to the round bottomed open flask at `27^(@) C` and put it one the flame After a lapse of time he realized his mistake using a pyrometer he found the temperature of the flask was `477^(@)C` What fraction of air would have been expelled out ? .

Explanation

Initial mole of air in flask `= n_(1)`
Temperature `= 27 +273 = 300 K`
Final mole of air in flask `=n_(2)`
Temperature ` =477 + 273 =750K`
The volume and pressure remains constant thus
`n_(1)T_(1) =n_(2)T_(2)`
`:. n_(2) = (n_(1)xx 300)/(750) = (2)/(5) n_(1)`
Thus, air expelled out on heating `= n_(1) - n_(2)`
`n_(1) - (2//5) n_(1) = (3)/(5) n_(1)`
or fraction of air expelled `=3//5` .