an open vessel at 37 is heated until ¾ of air is has been expelled .assuming volume of the vessel remains constant,the temperature to which vessel remain in the flask

Let the number of moles of air pesent in the vessel = n

75% means ¾ th of the original moles of gas has been expelled.

Therefore, the remaining number of moles of air in the vessel = (n – ¾ n)

   =  ¼ n

At constant pressure and volume,

n1T1= n2T2

n x 310 = ¼ n x T2

T2 = 1240 K = 967 degree Celcius

Hence, the temperature to which the vessel has been heated is 967 degree Celcius.