1.09 l of a gas at standard temperature and pressure is compressed to 374 ml. what is the new pressure of the gas?

This can be solved using the equation PV = nRT, but there is an easier way using Boyle's Law. This law states that the product of pressure and volume are constant in a system with constant temperature. This means that we can set the product of initial pressure and volume equal to the final pressure and volume. Maybe you have seen this equation as P1V1 = P2V2.  We know that temperature is constant at 0 degrees Celsius (or 273.15 K), and that the initial pressure is standard at 1 atmosphere (atm). This means our knowns are:
P1 = 1 atm    V1 = 1.09 L    V2 = 0.374 L (from 374 mL)
Plug these into the Boyle's Law equation P1V1 = P2V2:
(1 atm)*(1.09 L) = (P2) * (0.374 L)
(1 atm)*(1.09 L)/(0.374 L) = P2
P2 = 2.91 atm