Question

An ideal gas is allowed to expand both reversibly and irreversibly in an isolated system. If Ti is the initial temperature and Tf is the final temperature, which of the following statements is correct ?

• A. Tf> Ti for reversible process but Tf = Ti for irreversible process
• B. (Tf)rev = (Tf)irrev
• C. Tf = Ti for both reversible and irreversible processes
• D. (Tf)irrev> (Tf)rev

Answer 1

Answer: (D)

(Tf)irrev> (Tf)rev

Answer 2

In isolated system, the expansion of gas is carried out adiabatically. Since heat exchange between system and surrounding is not possible i.e. q = 0 and secondary wrev is always greater than wirr­ therefore for reversible process there must be comparatively higher decreases in internal energy i.e. $\Delta$U for reversible process will be more negative. Hence, final temperature in reversible process will be smaller than irreversible process.

\ (Tf)irrev > (Tf)rev