1. Unit: Gas Laws Gay-Lussac’s and Combined Gas Laws

2. After today you will be able to… Explain the effect on gas properties using Gay-Lussac’s Law and the Combined Gas Law Calculate an unknown pressure, temperature, or volume by solving algebraically

3. Gay-Lussac’s Law: Pressure and Temperature the relationship between temperature and pressure. Joseph Gay-Lussac discovered the relationship between temperature and pressure. His name is on the gas law that describes this relationship.

4. “For a given volume of a gas, as the temperature of an enclosed gas increases, the pressure of a gas is directly proportional.”

5. Gay-Lussac’s Law: Pressure and Temperature We can simplify this relationship by the formula: Where, pressure in any unit (atm, kPa, or mmHg), BUT they must match! P 1, P 2 = pressure in any unit (atm, kPa, or mmHg), BUT they must match! temperature is always in Kelvin! (Recall, just add 273 +°C) T 1, T 2 = temperature is always in Kelvin! (Recall, just add 273 +°C) P 1 P 2 T 1 T 2 =

6. Gay-Lussac’s Law: Example A gas has a pressure of 103kPa at 25°C. What will the pressure be when the temperature reaches 928°C? P1=P1= T1=T1= P2=P2= T2=T2= 103kPa 25°C +273= 298K ? 928°C+273= 1201K (103kPa) (298K) = (P 2 ) P2P2 = 420kPa P 1 P 2 T 1 T 2 = (1201K)

7. The Combined Gas Law The combined gas law is a single expression that combines Boyle’s, Charles’s, and Gay-Lussac’s Laws. temperature, pressure, and volume of a gas. This gas law describes the relationship between temperature, pressure, and volume of a gas. amount of gas is constant. It allows you to do calculations where only the amount of gas is constant. RB + JC + JG-L = BFFs!

8. The Combined Gas Law P 1 V 1 P 2 V 2 T 1 T 2 = no mention of temperature Boyle’s Law For example, if there is no mention of temperature in the problem, cover T up and you are left with the relationship between P and V. (aka Boyle’s Law!) no mention of pressure Charles’s Law If there is no mention of pressure in the problem, cover P up and you are left with the relationship between T and V. (aka Charles’s Law!) no mention of volume Gay-Lussac’s Law If there is no mention of volume in the problem, cover V up and you are left with the relationship between T and P. (aka Gay-Lussac’s Law!) Helpful hint: There is no need to memorize 4 individual laws Combined Gas Law Helpful hint: You are able to get which law you need by covering the variable that is not mentioned in the problem! There is no need to memorize 4 individual laws, just memorize the Combined Gas Law and you can derive all of the others!

9. The Combined Gas Law A gas occupies 3.78L at 529mmHg and 17.2°C. At what pressure would the volume of the gas be 4.54L if the temperature is increased to 34.8°C? P1=P1= V1=V1= T1=T1= P2=P2= V2=V2= T2=T2= 529mmHg 3.78L 17.2°C + 273= 290.2K ? (529mmHg) (290.2K) = (P 2 ) P2P2 = 467mmHg P 1 V 1 P 2 V 2 T 1 T 2 = (307.8K) 4.54L 34.8°C + 273= 307.8K (3.78L) (4.54L)

10. Questions? Complete WS 3