Answer:
20 atm
Step-by-step explanation:
Use the equation P1 x V1 = P2 x V2.
1) Rearrange the equation with algebra to solve for P2.
P2 = (P1 x V1)/ V2
2) Plug in to the equation where V1 = 25L, P1 = 0.80 atm, and, V2 = 1 L
P2 = (25L x 0.80 atm)/ 1L
3) Solve: P2 = 20 atm
The pressure required to reduce the oxygen's volume to 1 L would be 20 atm.