Question

A glass vessel contains air at 27° C. To what temperature must it be heated to expel one-fourth of the air, the pressure remaining constant.

Answer 1

a glass vessel contain air at to what

Answer 2

Answer:

102°C

Explanation:

now we have a flask, lets say of volume ‘V’ it is at 27 C . converting Celsius to kelvin we get 300K , this is what almost all workings contain.

now we say that 1/4th of the air is expelled, due to the expansion. but does this mean that this expelled air creates a vacuum in the flask? NO. so basically the place is taken by the air left in the flask which has expanded. now just for the sake of visualisation, lets consider the absence of the flask and the presence of this air in vacuum. so we said that 1/4th of V is out , but the remaining 3/4th is still in the flask but due to expansion it covers V volume. so now the total volume air present in total is V+1/4V =5/4V.

now using the basic gas laws we can say,

V1/T1=V2/T2

V/T=5/4V/T

V/300=5/4V/T

V and V cancel and we are left with the equation T=(5/4)*300

therefore T=375K, WHICH IS 102 C