In an isothermal process,which statement is wrong?

An ideal gas expands isothermally along $ab$ and does $600\,J$ of work. During the process,

Two identical vessels $A$ and $B$ with frictionless pistons contain the same ideal gas at the same temperature and the same volume $V$. The masses of gas in $A$ and $B$ are $m_A$ and $m_B$, respectively. The gases are allowed to expand isothermally to the same final volume $2V$. The changes in pressures of the gas in $A$ and $B$ are found to be $\Delta P$ and $1.5 \Delta P$, respectively. Then

$A$ sample of an ideal gas undergoes an isothermal expansion. If $dQ$,$dU$,and $dW$ represent the amount of heat supplied,the change in internal energy,and the work done respectively,then:

Write the first law of thermodynamics for an isothermal expansion process.

The work done in doubling the volume of $5$ moles of an ideal gas at a constant temperature of $500 \, K$ is ....... $J$.