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### 12.3

1. 1. Putting it all together… Chapter 12 section 3 Slides 1-5 = Ideal Gas Law
2. 2. Ideal Gas Law Relates 4 Gas Variables <ul><li>PV = nRT </li></ul><ul><li>The value for R depends on the units used for pressure and volume. </li></ul><ul><li>Volume must be in liters </li></ul>
3. 3. R <ul><li>For problems that use units of kilopascals and liters when using the ideal gas law, the value you will use for R is as follows. </li></ul><ul><li>If the pressure is expressed in atmospheres , then the value of R is 0.08206 (L•atm)/(mol•K) . </li></ul>
4. 4. Ideal Gas Law Sample Problem How many moles of gas are contained in 22.41 liters at 101.325 kPa and 0°C?
5. 5. 1.00 mol Ideal Gas Law Sample Problem Solution V = 22.41 L T = 0°C P = 101.325 kPa n = ? 0°C + 273 = 273 K PV = nRT
6. 6. Diffusion <ul><li>Gaseous molecules travel at high speeds in all directions and mix quickly with molecules of gases in the air in a process called diffusion. </li></ul><ul><li>Diffusion is the movement of particles from regions of higher density to regions of lower density. </li></ul><ul><li>During diffusion, a substance moves from a region of high concentration to a region of lower concentration . </li></ul><ul><li>Eventually, the mixture becomes homogeneous. </li></ul><ul><li>Large molecules diffuse slower than small molecules. </li></ul>
7. 7. Dalton’s Law of Partial Pressure <ul><li>In 1805, John Dalton showed that in a mixture of gases, each gas exerts a certain pressure as if it were alone with no other gases mixed with it. </li></ul><ul><li>The pressure of each gas in a mixture is called the partial pressure. </li></ul><ul><li>The total pressure of a mixture of gases is the sum of the partial pressures of the gases. This principle is known as Dalton’s law of partial pressure. </li></ul>
8. 8. Dalton’s Law of Partial Pressure <ul><li>Dalton’s law of partial pressure can be written as follows. </li></ul><ul><li>P total = P A + P B + P C </li></ul><ul><ul><li>P total is the total pressure, and P A , P B , and P C are the partial pressures of each gas. </li></ul></ul>
9. 9. Gas Volumes Correspond to Mole Ratios <ul><li>Ratios of gas volumes will be the same as mole ratios of gases in balanced equations. </li></ul><ul><li>Avogadro’s law shows that the mole ratio of two gases at the same temperature and pressure is the same as the volume ratio of the two gases. </li></ul>
10. 10. Gas Volumes Correspond to Mole Ratios <ul><li>For example, consider the following equation for the production of ammonia. </li></ul><ul><li>3 H 2 ( g ) + N 2 ( g ) -> 2 NH 3 ( g ) </li></ul><ul><li>3 L of H 2 react with 1 L of N 2 to form 2 L of NH 3 , and no H 2 or N 2 is left over </li></ul><ul><li>If we know the number of moles of a gaseous substance, we can use the ideal gas law to calculate the volume of that gas. </li></ul>