Question

One mole of an ideal gas is taken from state $P$ to state $Q$ by three different processes (i) $PRQ$, (ii) $PSQ$ and (iii) $PTQ$ as shown in the $p-V$ diagram. The heat absorbed by the gas is

• A. The least in process (ii)
• B. Greater in process (ii) than in process (i)
• C. The same in the processes (i) and (ii)
• D. Less in process (iii) than in process (ii)

Answer 1

The correct option is D Less in process (iii) than in process (ii)

Heat absorbed by gas in three processes can be written as
$△Q_{PRQ}=△U+W_{PRQ}$
$△Q_{PSQ}=△U$
$△Q_{PTQ}=△U+W_{PTQ}$
The change in internal energy in all the three cases is same and $△W_{PRQ}>0,△W_{PTQ}<0$
Hence, $△Q_{PRQ}>△Q_{PSQ}>△Q_{PTQ}$.