DALTON'S LAW OF PARTIAL PRESSURES According to Dalton's law, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the gases in the mixture. Zn(s) + NH4NO3(s) → N2(g) + 2 H2O(g)  + ZnO(s)

PARTIAL PRESSURE The partial pressure of an individual gas of a mixture is the pressure the gas would exert if it were alone in the container at the same temperature as the mixture as shown in the following illustration:

GRAHAM'S LAW Graham's law is a mathematical expression that relates the rates of effusion or diffusion of two gases to the masses of the molecules of the two gases. EFFUSION Effusion is a process in which a gas escapes from a container through a small hole in the container. DIFFUSION Diffusion is a process that causes gases to spontaneously mix when they are brought together.

MATHEMATICAL EXPRESSION OF GRAHAM'S LAW

GRAHAM'S LAW CALCULATION EXAMPLE Compare the rates of effusion or diffusion for neon and krypton gases. Solution: The molecular masses of neon and krypton are 20.18 u and 83.80 u, respectively. These are the molecular weights of the gases from the periodic table. Substitution into the Graham's law equation gives the following: Thus, the rate of Ne = (2.038) rate of Kr. Stated another way, neon gas effuses or diffuses about twice as fast as krypton gas.

CHANGES IN STATE Changes in state are often accomplished by adding or removing heat from a substance. Changes in state caused by adding heat to a substance are classified as endothermic (heat in) processes. Changes in state caused by removing heat are classified as exothermic (heat out) processes.

ENDOTHERMIC PROCESSES EVAPORATION OR VAPORIZATION Evaporation or vaporization is an endothermic process in which a liquid is changed to a gas. SUBLIMATION Sublimation is an endothermic process in which a solid is changed to a gas without first melting to a liquid. MELTING OR FUSION Melting or fusion is an endothermic process in which a solid is changed to a liquid.

EXOTHERMIC PROCESSES LIQUEFACTION OR CONDENSATION Liquefaction or condensation is an exothermic process in which a gas is changed to a liquid. DEPOSITION OR CONDENSATION Deposition or condensation is an exothermic process in which a gas is changed into a solid. FREEZING OR CRYSTALLIZATION Freezing or crystallization is an exothermic process in which a liquid is changed into a solid.

VAPOR PRESSURE Vapor pressure is the pressure exerted by a vapor that is in equilibrium with its liquid.

BOILING POINT The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to the prevailing atmospheric pressure. The normal or standard boiling point is the temperature at which the vapor pressure of a liquid is equal to 1 standard atmosphere (760 torr).

VARIATION OF WATER BOILING POINT WITH ELEVATION

SUBLIMATION AND MELTING Sublimation is the endothermic process in which a solid is changed directly to a gas without first becoming a liquid.

ENERGY AND THE STATES OF MATTER At 760 torr, constant heat is applied until a 1 g sample of ice at -20°C is converted to steam at 120°C. This is a five step process: (AB) heating ice to melting point, (BC) melting ice, (CD) heating liquid to boiling point, (DE) boiling water, and (EF) heating steam.

SPECIFIC HEAT The specific heat of a substance is the amount of heat required to raise the temperature of exactly 1 g of a substance exactly 1°C.

HEATS OF FUSION & VAPORIZATION HEAT OF FUSION The heat of fusion of a substance is the amount of heat required to melt exactly 1g of a solid substance at constant temperature. HEAT OF VAPORIZATION The heat of vaporization of a substance is the amount of heat required to vaporize exactly 1g of a liquid substance at constant temperature.