What are the standard conditions (STP) for temperature and pressure? Bellwork: Look up the answers to these questions. You may use your phone. What are the standard conditions (STP) for temperature and pressure? What does absolute zero mean as it relates to temperature? Define Temperature. Which temperature scale is temperature directly proportional to average kinetic energy? Under what conditions do gases behave most like ideal gases?

A sample of nitrogen gas has a pressure of 6. 58 kPa at 266°C A sample of nitrogen gas has a pressure of 6.58 kPa at 266°C. If the volume does not change, what will the pressure be at 211K? A gas at 155 kPa and 25°C has an initial volume of 1.00 L. The pressure of the gas increases to 605 kPa as the temperature raises to 125 °C. What is the new volume?

A sample of nitrogen gas has a pressure of 6. 58 kPa at 266°C A sample of nitrogen gas has a pressure of 6.58 kPa at 266°C. If the volume does not change, what will the pressure be at 211K?

A gas at 155 kPa and 25°C has an initial volume of 1.00 L. The pressure of the gas increases to 605 kPa as the temperature raises to 125 °C. What is the new volume?

4 things In order to completely describe a gas you need to measure 4 things Pressure Temperature Volume Number of particles

Force Pressure = Area 1 atm = 760 mmHg = 760 torr 1 atm = 101.3 kPa Barometer Pressure = 1 atm = 760 mmHg = 760 torr 1 atm = 101.3 kPa

Atmospheric Pressure Atmospheric pressure varies with Altitude the lower the altitude, the longer and heavier is the column of air above an area of the earth. Cake Boxes

Pressure and the number of molecules are directly related More molecules means more collisions Fewer molecules means fewer collisions.

Each of these flasks contains the same number of molecules Each of these flasks contains the same number of molecules. In which container is the pressure highest? A. Flask 4 B. Flask 3 C. Flask 2 D. Flask 1

Each of these flasks is the same size and at the same temperature Each of these flasks is the same size and at the same temperature. Which one contains the fewest molecules? A. Flask 1 B. Flask 2 C. Flask 3 D. Flask 4

Ideal Gases We are going to assume the gases behave ideally Does not really exist makes the math easier close approximation. Assume particles have no volume Assume no attractive forces between molecules

Ideal Gases There are no gases for which this is true. Real gases behave this way at high temperature and low pressure.

Dalton’s Law of Partial Pressures The total pressure inside a container is equal to the sum of the partial pressure due to each gas. The partial pressure of a gas is the contribution by that gas hitting the wall. PTotal = P1 + P2 + P3 + …

We can find out the pressure in the fourth container By adding up the pressure in the first 3 2 atm 1 atm 3 atm 6 atm

If the total pressure of a system was 2 If the total pressure of a system was 2.5 atm, what is the partial pressure of carbon monoxide if the gas mixture also contained 0.4 atm O2 and 1.48 atm of N2?

Examples What is the total pressure in a balloon filled with air if the pressure of the oxygen is 170 mm Hg and the pressure of nitrogen is 620 mm Hg?

Avogadro’s Hypothesis V is proportional to number of molecules at constant T and P. V is proportional to moles. V1 = V2 n1 n2 V is the volume n is chemical amount (mol)

A 6. 0 L sample at 25 °C and 2. 00 atm of pressure contains 0 A 6.0 L sample at 25 °C and 2.00 atm of pressure contains 0.5 moles of a gas. If an additional 0.25 moles of gas at the same pressure and temperature are added, what is the final total volume of the gas?

= R = K Avogadro’s Hypothesis Gets put into the combined gas law P1 x V1 = P2 x V2 n1 x T1 n1 x T2 = R = K

The Ideal Gas Law P x V = n x R x T

The Ideal Gas Constant R = 0.0821 (L atm) (mol K) R = 8.31 (L kPa) (K mol)

The Ideal Gas Law PV = nRT We now have a new way to count moles of a gas. By measuring T, P, and V. We aren’t restricted to STP. n = PV/RT Nothing is required to change, No 1’s and 2’s

Example How many moles of air are there in a 2.0 L bottle at 19ºC and 747 mm Hg?

The Ideal Gas Constant R = 0.0821 (L atm) (mol K) R = 8.31 (L kPa) (K mol)

Example What is the pressure exerted by 1.8 g of H2 gas exert in a 4.3 L balloon at 27ºC?

The Ideal Gas Constant R = 0.0821 (L atm) (mol K) R = 8.31 (L kPa) (K mol)