Arigid cylinder with a movable piston contains 50.0 liters of a gas at 30.0 degree c with a pressure of 1.00 atmosphere. what is the volume of the gas in the cylinder at stp?
(1) 5.49 l (3) 55.5 l
(2) 45.0 l (4) 455 l

Charles law states that volume of a gas is directly proportional to temperature at constant pressure for a fixed amount of gas. the pressure at given conditions is 1.00 atm and the standard pressure at STP conditions too is 1.00 atm therefore pressure remains constant.
 V1/T1 = V2/T2
the parameters for the first instance are on the left side and parameters at STP are on the right side of the equation.
T1 - temperature in kelvin - 273 + 30.0 °C = 303 K
T2 - standard temperature - 273 K
V1 - volume - 50.0 L
substituting the values in the equation
50.0 L / 303 K = V / 273 K V = 45.0 L
answer is 2) 45.0 L