# During an isothermal expansion, a confined ideal gas does $-150 J$ of work against its surroundings. This implies that: Option 1) 150 J heat has been removed from the gas Option 2) 300 J of heat has been added to the gas Option 3) No heat is transferred because the process is isothermal  Option 4) 150 J of heat has been added to the gas

Using

First law in Isothermal Process -

$\Delta Q= \Delta U+\Delta W$

- wherein

Isothermal process

$\Delta T= 0$

$\Delta U= 0$

Heat supplied is equal to work done.

Negative work done by gas implies work is done on the system.

$Q = \Delta U+W \ \ \ -(i)$

For isothermal process, $\Delta U =0$

$\therefore Q= W =-150\ T$

Hence, heat is given to the system.

Option 1)

150 J heat has been removed from the gas

This option is incorrect

Option 2)

300 J of heat has been added to the gas

This option is incorrect

Option 3)

No heat is transferred because the process is isothermal

This option is incorrect

Option 4)

150 J of heat has been added to the gas

This option is correct

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