0.040 g of He is kept in a closed container initially at 100.0°C. The container is now heated. Neglecting the expansion of the container, calculate the temperature at which the internal energy is increased by 12 J.

Given


Mass of helium =0.040g


Molar mass of helium=4g/mol


Number of moles n=


Number of moles for helium n=


Temperature T1=100


T(K)=T ()+273.15


T=T(K)=100+273.15=373.15K


Internal energy U in kinetic theory is given as



Where Cv= molar specific heat capacity


N= number of moles


T=temperature of gas


Also, internal energy depends only the temperature of the gas.


Helium is a monoatomic gas and for monoatomic gas



So, Cv for helium is Jmol-1K-1


Increase in internal energy is given in question as 12J. That means


U2-U1= nCv(T2-T1)


Since the gas has not been changed, just expanded no change in molar specific heat capacity and number of moles of gas.


Putting the value of change in internal energy and T1,


12=0.0112.45(T2-373.15)



The temperature at which the internal energy is increased by 12J is 469.53J =196.38.


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