1.

For an idealgas, the work of reversible expansion under isothermal condition can be calculated by using the expression w= - nRT ln . (V_(f))/( V_(i)0 . A sample containig 1.0 molof an ideal gas is expanded isothermally and reversibly to ten times of its original volume in two separate experiments . The expansions is carried out at 300 K and at600 K respectively. Choose the correct option.

Answer»

WORK done at 600 K is 20 times at the work done at 300K
Work done at 300 K is twice the work done at 600 K
Work done at 600 K is twicethe work done at 300 K
`DeltaU=0`in both cases

Solution :`w= -nRT LN. (V_(1))/( V_(2)). `The factors n , R and `ln. (V_(f))/( V_(i))` are same in both the cases. Hence, `(w_(2))/(w_(1)) = (T_(2))/(T_(1)), i.e., (.^(w)600K)/(.^(w)300K)= ( 600K)/( 300K) =2 , i.e., ` work done at 600K is twice thework done at 300K.
As each case involves ISOTHERMAL expansion of an ideal gas, there is no change in internal energy, i.e.,
`DeltaU =0`


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