The Gas Laws Learning about the special behavior of gases Objective #2, begins on pg. 5 of the Note pack

Combined Gas Law: There really is no need to remember 3 different equations combined gas law A single expression, called the combined gas law, combines the three gas laws, only holding the amount of gas constant..

Re-arranging the Combined Gas Law This is not in your notes, but perhaps it should be. You will need to be able to solve for 1 variable, when given the other 5. To do that, you will need to re-arrange the formula. Q: How do you isolate just 1 variable? A: Criss-cross the other variables, that are with it, to the other side of the equation.

Example, to solve for V 1 … (how to get V 1 all by itself) P 1 V 1 P 2 V 2 T 1 T 2 Re-arranging the Combined Gas Law

Example, to solve for V 1 … Move the P1, to the bottom… P 1 V 1 P 2 V 2 T 1 T 2 Re-arranging the Combined Gas Law

Example, to solve for V 1 … Then move the T 1, to the top… V 1 P 2 V 2 T 1 T 2 P 1 Re-arranging the Combined Gas Law

Example, to solve for V 1 … V 1 P 2 V 2 T 1 T 2 P 1 Re-arranging the Combined Gas Law

Your turn… With your neighbor, please write the formula you would use to find each of the following: V 1 = V 2 = T 1 = T 2 = P 1 = P 2 =

Your turn… With your neighbor, please write the formula you would use to find each of the following: V 1 = V 2 = T 1 = T 2 = P 1 = P 2 = P 2 V 2 T 1 T 2 P 1 P 2 V 2 T 1 P 1 V 1 P 2 V 2 T 1 T 2 V 1 P 1 V 1 T 2 T 1 P 2 P 1 V 1 T 2 P 2 V 2 P 1 V 1 T 2 T 1 V 2 We can not have 1 / T 1 as a legitimate option, so the formula must be inverted.

Example 1 The volume of a gas-filled balloon is 30.0 L at 40 o C and 153 kPa pressure. What volume will the balloon have at standard temperature and pressure?

Example 1 The volume of a gas-filled balloon is 30.0 L at 40 o C and 153 kPa pressure. What volume will the balloon have at standard temperature and pressure? First, determine what formula we’re going to use to find what’s missing:

Example 1 The volume of a gas-filled balloon is 30.0 L at 40 o C and 153 kPa pressure. What volume will the balloon have at standard temperature and pressure? First, determine what formula we’re going to use to find what’s missing: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1

Example 1 The volume of a gas-filled balloon is 30.0 L at 40 o C and 153 kPa pressure. What volume will the balloon have at standard temperature and pressure? First, determine what formula we’re going to use to find what’s missing: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1 Now substitute, changing the temp to Kelvin:

Example 1 The volume of a gas-filled balloon is 30.0 L at 40 o C and 153 kPa pressure. What volume will the balloon have at standard temperature and pressure? First, determine what formula we’re going to use to find what’s missing: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1 Now substitute, changing the temp to Kelvin: V 2 =(30 L)x(153 kPa)x(273K) (101.3kPa)x(313K)

Example 1 The volume of a gas-filled balloon is 30.0 L at 40 o C and 153 kPa pressure. What volume will the balloon have at standard temperature and pressure? First, determine what formula we’re going to use to find what’s missing: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1 Now substitute, changing the temp to Kelvin: V 2 =(30 L)x(153 kPa)x(273K) (101.3kPa)x(313K) V 2 = 39.5 L

Example 2 A gas at 155 kPa and 25 o C occupies a container with an initial volume of 1 L. By changing the volume, the pressure of a gas increases to 605 kPa as the temperature is raised to 125 o C. What is the new volume?

Example 2 A gas at 155 kPa and 25 o C occupies a container with an initial volume of 1 L. By changing the volume, the pressure of a gas increases to 605 kPa as the temperature is raised to 125 o C. What is the new volume? First, determine what formula we’re going to use to find what’s missing:

Example 2 A gas at 155 kPa and 25 o C occupies a container with an initial volume of 1 L. By changing the volume, the pressure of a gas increases to 605 kPa as the temperature is raised to 125 o C. What is the new volume? First, determine what formula we’re going to use to find what’s missing: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1

Example 2 A gas at 155 kPa and 25 o C occupies a container with an initial volume of 1 L. By changing the volume, the pressure of a gas increases to 605 kPa as the temperature is raised to 125 o C. What is the new volume? First, determine what formula we’re going to use to find what’s missing: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1 Now substitute, changing the temp to Kelvin:

Example 2 A gas at 155 kPa and 25 o C occupies a container with an initial volume of 1 L. By changing the volume, the pressure of a gas increases to 605 kPa as the temperature is raised to 125 o C. What is the new volume? First, determine what formula we’re going to use to find what’s missing: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1 Now substitute, changing the temp to Kelvin: V 2 =(1L)x(155kPa)x(398K) (605kPa)x(298K)

Example 2 A gas at 155 kPa and 25 o C occupies a container with an initial volume of 1 L. By changing the volume, the pressure of a gas increases to 605 kPa as the temperature is raised to 125 o C. What is the new volume? First, determine what formula we’re going to use to find what’s missing: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1 Now substitute, changing the temp to Kelvin: V 2 =(1L)x(155kPa)x(398K) (605kPa)x(298K) V 2 = L

Example 3 A 5 L air sample at a temperature of – 50 o C has a pressure of 107 kPa. What will be the new pressure if the temperature is raised to 102 o C and the volume expands to 7 L?

Example 3 A 5 L air sample at a temperature of – 50 o C has a pressure of 107 kPa. What will be the new pressure if the temperature is raised to 102 o C and the volume expands to 7 L? First, determine what formula we’re going to use to find what’s missing:

Example 3 A 5 L air sample at a temperature of – 50 o C has a pressure of 107 kPa. What will be the new pressure if the temperature is raised to 102 o C and the volume expands to 7 L? First, determine what formula we’re going to use to find what’s missing: We’re finding P 2 = V 1 x P 1 x T 2 V 2 x T 1

Example 3 A 5 L air sample at a temperature of – 50 o C has a pressure of 107 kPa. What will be the new pressure if the temperature is raised to 102 o C and the volume expands to 7 L? First, determine what formula we’re going to use to find what’s missing: We’re finding P 2 = V 1 x P 1 x T 2 V 2 x T 1 Now substitute, changing the temp to Kelvin:

Example 3 A 5 L air sample at a temperature of – 50 o C has a pressure of 107 kPa. What will be the new pressure if the temperature is raised to 102 o C and the volume expands to 7 L? First, determine what formula we’re going to use to find what’s missing: We’re finding P 2 = V 1 x P 1 x T 2 V 2 x T 1 Now substitute, changing the temp to Kelvin: P 2 =(5L)x(107kPa)x(375K) (7L)x(223K)

Example 3 A 5 L air sample at a temperature of – 50 o C has a pressure of 107 kPa. What will be the new pressure if the temperature is raised to 102 o C and the volume expands to 7 L? First, determine what formula we’re going to use to find what’s missing: We’re finding P 2 = V 1 x P 1 x T 2 V 2 x T 1 Now substitute, changing the temp to Kelvin: P 2 =(5L)x(107kPa)x(375K) (7L)x(223K) P 2 = kPa

Example 4 A given mass of air has a volume of 6 L at 101 kPa. What volume will it occupy at 25 kPa if the temperature does not change?

Example 4 A given mass of air has a volume of 6 L at 101 kPa. What volume will it occupy at 25 kPa if the temperature does not change? First, determine what formula we’re going to use to find what’s missing. Since temp doesn’t change, T 1 and T 2 cancel each other out:

Example 4 A given mass of air has a volume of 6 L at 101 kPa. What volume will it occupy at 25 kPa if the temperature does not change? First, determine what formula we’re going to use to find what’s missing. Since temp doesn’t change, T 1 and T 2 cancel each other out: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1

Example 4 A given mass of air has a volume of 6 L at 101 kPa. What volume will it occupy at 25 kPa if the temperature does not change? First, determine what formula we’re going to use to find what’s missing. Since temp doesn’t change, T 1 and T 2 cancel each other out: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1 Now substitute, changing the temp to Kelvin: V 2 = (6L)x(101kPa) (25kPa)

Example 4 A given mass of air has a volume of 6 L at 101 kPa. What volume will it occupy at 25 kPa if the temperature does not change? First, determine what formula we’re going to use to find what’s missing. Since temp doesn’t change, T 1 and T 2 cancel each other out: We’re finding V 2 = V 1 x P 1 x T 2 P 2 x T 1 Now substitute, changing the temp to Kelvin: V 2 = (6L)x(101kPa) (25kPa) V 2 = 24.24L

A Word of Caution!! When we’re trying to find an unknown Temp., like T 2 … P 1 V 1 P 2 V 2 T 1 T 2 =

A Word of Caution!! When we’re trying to find an unknown Temp., like T 2 … P 1 V 1 P 2 V 2 T 1 T 2 =

A Word of Caution!! When we’re trying to find an unknown Temp., like T 2 … P 1 V 1 P 2 V 2 So we have P 1 V 1 1 T 1 T 2 P 2 V 2 T 1 T 2 This doesn’t work, to have 1 / T 2 = =

A Word of Caution!! When we’re trying to find an unknown Temp., like T 2 … P 1 V 1 P 2 V 2 So we have P 1 V 1 1 T 1 T 2 P 2 V 2 T 1 T 2 invert To fix this, we need to invert both sides: ==

A Word of Caution!! When we’re trying to find an unknown Temp., like T 2 … P 1 V 1 P 2 V 2 So we have P 1 V 1 1 T 1 T 2 P 2 V 2 T 1 T 2 To fix this, we need to invert both sides: P 2 V 2 T 1 T 2 P 1 V 1 = = =

Practice… Practice!! Now you know how to do MOST of Objective #2 (we’ll do the rest a little later…) Next part is “Collecting a gas over water”