A 425-ml sample of hydrogen is collected above water at 35°c and 763 torr. find the volume of the hydrogen sample when the temperature falls to 23°c, assuming the barometric pressure does not change. (vapor pressures of water : at 35°c, 42.2 torr; at 23°c, 21.1 torr)

From the gas laws, Charles law states that the volume of a fixed mas of a gas is directly proportional to absolute temperature at constant pressure.

and Boyle's law states that the volume of a fixed mass of a gas is inversely proportional to pressure at constant temperature, therefore combining the two we have, PV/T, for two gases we have,

P1V1/T1=P2V2/T2

V1 = 425 ml, T1 = 35 + 273 = 308 K, P1 = 805.2 torr

V2 = ? and T2 = 23 + 273 = 296K, P2 = 784.1torr

V2 = P1V1T2/P2T1

= (805.2*425*296) / 784*308

= 419.486 ml

= 419.5 ml