Answer : The final volume at STP is, 1000 L
Explanation :
According to the Boyle's, law, the pressure of the gas is inversely proportional to the volume of gas at constant temperature and moles of gas.

or,

where,
= initial pressure = 1520 mmHg = 2 atm (1 atm = 760 mmHg)
= final pressure at STP = 1 atm
= initial volume = 500.0 L
= final volume at STP = ?
Now put all the given values in the above formula, we get:


Therefore, the final volume at STP is, 1000 L