Answer : The volume of hydrogen gas at STP is 4550 L.
Explanation :
Combined gas law is the combination of Boyle's law, Charles's law and Gay-Lussac's law.
The combined gas equation is,

where,
= initial pressure of gas = 100.0 atm
= final pressure of gas at STP = 1 atm
= initial volume of gas = 50.0 L
= final volume of gas at STP = ?
= initial temperature of gas = 
= final temperature of gas at STP = 
Now put all the given values in the above equation, we get:


Therefore, the volume of hydrogen gas at STP is 4550 L.