Initial temperature is given as,
T1=27+273
=300K
If initially the numbers of molecules are n and after escape out the left molecules will be 23n.
Since, the pressure is constant and the temperature is inversely proportional to the numbers of molecules.
It can be written as,
T1T2=n2n1
300T2=23nn
T2=450K
=177∘C
Thus, the heating temperature is 177∘C.