Themes > Science > Chemistry > Inorganic Chemistry > More Information About Gas Laws > The Gas Law > Dalton's Law Dalton's Law of Partial Pressure: used with a mixture of gases. The total pressure in a container is the sum of the partial pressures of all the gases in the container. When a gas is collected by water displacement in the lab, the collected sample will contain water vapor. A calculation using Dalton's Law must be used to determine the pressure of the dry gas (the gas with no water vapor). To do this calculation, you will need the vapor pressure of water at the collected temperature.Portfolio Assignment 213: Scoring criteria   Work the following Dalton' Law practice problems: The total pressure in a closed container of three mixed gases is 96.4 kPa. The partial pressure of hydrogen in the mixture is 13.5 kPa and the partial pressure of oxygen is 29.3 kPa. The third gas in the mixture is methane, what is its partial pressure? 100 cm3 of hydrogen gas are collected using water displacement in the lab. The conditions at the time are 98.5 kPa and 24 oC. What volume of dry hydrogen is collected? 325 cm3 of oxygen are collected over water at 10 oC and 98 kPa. What will be the volume of the dry gas at 101 kPa and 10 oC? Information provided by: http://pc65.frontier.osrhe.edu