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Per NCERT §5.2.1 + eqn 5.5, for an isothermal REVERSIBLE expansion of n mol of an ideal gas from V_i to V_f, work done on the gas is which expression?
Aw_rev = nRT × ΔV
Bw_rev = −nRT ln(V_f/V_i) = −2.303 nRT log(V_f/V_i)
Cw_rev = pΔV only
Dw_rev = +nRT ln(V_f/V_i)
Answer & Solution
Correct answer: B. w_rev = −nRT ln(V_f/V_i) = −2.303 nRT log(V_f/V_i)
Per NCERT eqn 5.5, w_rev = −nRT ln(V_f/V_i). For expansion V_f>V_i ⇒ w_rev<0 (gas does work on surroundings).
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