Engineering Chemistry 14/15 Fall semester Instructor: Rama Oktavian Office Hr.: M.13-15, Tu , W , Th , F

Outlines 1. Ideal gas properties 2. Molar mass of gas 3. Molar mass of volatile component 4. Gas mixture

Review Learning check A sealed flask with a capacity of 1 dm 3 contains 5 g of ethane. The flask is so weak that it will burst if the pressure exceeds 1 MPa. At what temperature will the pressure of the gas reach the bursting pressure ?

Review Learning check A perfect gas undergoes isothermal compression, which reduces its volume by 1.80 dm 3. The final pressure and volume of the gas are 1.97 bar and 2.14 dm 3, respectively. Calculate the original pressure of the gas in (a) bar, (b) Torr

Review Learning check A large cylinder for storing compressed gases has a volume of about m3. If the gas is stored under a pressure of 15 MPa at 300 K, how many moles of gas are contained in the cylinder ? What would be the mass of oxygen in such a cylinder ?

Ideal gas and Real gas Ideal gas The ideal gas law is used to describe the behavior of an ideal gas. Ideal gas: hypothetical gas that obeys kinetic molecular theory and the ideal gas law

Ideal gas and Real gas Ideal gas The ideal gas law was useful in determining the properties of a specific sample of gas at constant T, P, V, and n. We often need to know how a change in one (or more) properties impacts the other properties for a sample of a gas

Ideal gas and Real gas Real gas deviations from the perfect gas law because molecules interact with one another Repulsive forces are significant only when molecules are almost in contact Attractive intermolecular forces have a relatively long range and are effective over several molecular diameters

Molar mass of ideal gas Determination of molar mass for ideal gas Ideal gas equation Intensive properties and measurable

Molar mass of ideal gas Determination of molar mass for ideal gas Gas density Density is higher 1. for gases with a higher molar mass Gases 2. at higher pressures 3. at lower temperatures

Gas mixture Air is an example of an ideal gas mixture and has the following approximate composition. Component % by Volume N O Argon 0.92 CO2 + trace elements 0.03

Gas mixture Properties of gas mixture k gases T = T m V = V m P = P m m = m m The total mass of the mixture m m and the total moles of mixture N m are defined as

Gas mixture Properties of gas mixture Volume concentration Unit : mol/m 3 Volume concentration  molarity

Gas mixture Properties of gas mixture The composition of a gas mixture is described by specifying either the mass fraction mf i or the mole fraction y i of each component i. Note that

Dalton’s law Ideal gas law for gas mixture We define the partial pressure of each gas in the mixture as the pressure the gas would exert if it were alone in the container of volume V at temperature T

Dalton’s law Partial pressure Dalton’s law

Dalton’s Law of Partial Pressures indicates that pressure depends on the total number of gas particles, not on the types of particles. the total pressure exerted by gases in a mixture is the sum of the partial pressures of those gases. P T = P 1 + P 2 + P

Dalton’s law

Partial pressures are simply related to the mole fractions of the gases in the mixture

Dalton’s law Partial pressures are simply related to the mole fractions of the gases in the mixture

Dalton’s law Learning check If I place 3 moles of N 2 and 4 moles of O 2 in a 35 L container at a temperature of 25°C, what will the pressure of the resulting mixture of gases be? What’s the partial pressure of carbon dioxide in a container that holds 5 moles of carbon dioxide, 3 moles of nitrogen, and 1 mole of hydrogen and has a total pressure of 1.05 atm?

Dalton’s law Learning check A vessel of volume 22.4 dm3contains 1.5 mol H2and 2.5 mol N2 at K. Calculate (a) the mole fractions of each component, (b) their partial pressures, and (c) their total pressure

Dalton’s law Dalton’s law application in atmosphere This explains why people usually difficult to breathe in high altitude place even the concentration of oxygen is same (21%) The transfer of oxygen molecules from the lungs to the bloodstream is dependent on a pressure gradient.