Q24 of 31 Page 94

A balloon has 5.0 g mole of helium at 7°C. Calculate

(a) the number of atoms of helium in the balloon,


(b) the total internal energy of the system.


Given:


No. of moles of helium gas in the balloon n=5


Temperature of gas T= 7° C= 280K


(a) no. of atoms in a mole of gas =


∴ no. of atoms in 5 mole of gas =


(b) Total energy of gas is given by formula



Where R=universal gas constant =8.314 J/K-mol


Putting all the values in the above equation, we get



Therefore the total energy of the system is


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