A magician friend asks for your help in designing an illusion involving a "frozen" balloon containing 5.0 L of air at 0°C out of a freezer & heat it with a small explosive charge.

He needs to know how much heat energy will be required to raise the temperature to

20°C.

The molar specific heat of air at constant volume is 2.5 R.

Neglecting the tension in the balloon's latex, what do you tell him?

Ex 18.75

0 1: Exposive raises T of gas isovolumically.1 2: Gas expand adiabatically.Since surface tension of balloon is negligible, P0 = P2 = 1 atm.Other lines are isotherms.

Known: P0 , V0 , T0 , P2 , T2 , Cv .

0

22.4

Vn 1 0V V 2

22

n R TV

P

v

v

C R

C

1

21 2

1

VT T

V

1 0vQ n C T T