A balloon contains 5L of oxygen at a pressure of 90 kPa. How much oxygen will the ballon contain if the pressure is lowered to 67 kPa.

1 - According to this formula:

P1V1 = P2V2

2-By converting P from KPa to atm:

1 KPa = 0.00986923267 atm

So,

P1 = 0.888231 atm

P2 = 0.661239 atm

by substitution on the previous formula:

P1V1 = P2V2

0.888231 x 5 = 0.661239 x V2

So,

V2 (for the oxygen will the ballon contain) = 6.7 L