A. Work done at 600 K is 20 times the work done at 300 K
B. work done at 300K is twice the work done at 600 K
C. work done at 600 K is twice the work done at 300 K
D. `Delta U = 0` in both cases
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Correct Answer – c,d
`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 the work done at 300K.
As each case involves isothermal expansion of an ideal gas, there is no change in internal energy, i.e.,
`DeltaU =0`
Correct Answer – C::D
Given that, the work of reversible expansion under isothernal condition can be calculated by using the expression
`W = – nRT ln. (V_(1))/(V_(1))`
`V_(1) = 10 V_(i)`
`T_(2) = 600 K`
`T_(1) = 300 K`
Putting these values in above expression
`W_(600 K) = 1 xx R xx 600 ln. (10)/(1)`
`W_(300 K) = 1 xx R xx 300 K ln. (10)/(1)`
Ration `= (W_(600 K))/(W_(300 K)) = (1 xx R xx 600 K ln.(10)/(1))/(1 xx R xx 300 K ln. (10)/(1)) = (600)/(300) = 2`
For isothermal expansion of ideal gases, `Delta U = 0`. Since, temperature is contant this means there is no change in internal energy. Therefore, `Delta U = 0`
Correct Answer – C::D
`w = -nRT ln.(V_(f))/(V_(i))` Here, n, R and `ln.(V_(f))/(V_(i))` are same in both the cases therefore
`(w_(2))/(w_(1)) = (T_(2))/(T_(1))` or `(w(600K))/(w(300K)) = (600K)/(300K) = 2`