2. Temperature Unit Kelvin (K) Kelvin = °C + 273

3. Temperature Convert 45°C to Kelvin 45°C + 273 = 318 K

4. Temperature Absolute zero – 0 K Molecules stop moving Question: what is absolute zero temperature in Celsius? -273°C

5. Volume Units: mL L

6. Amount Units grams moles

7. Gas Laws Each gas law relates the 4 variables: Pressure Temperature Volume Amount For the next 4 gas laws, amount is not a factor We will only pay attention to P, T, & V

8. Boyles’ Law: P/V relationship Defn – at constant T, volume of a fixed amount of gas varies inversely with pressure inversely – as one variable increases, other variable decreases P V

9. Boyle’s Law Formula P 1 V 1 = P 2 V 2 P 1 & V 1 are initial conditions P 2 & V 2 are final conditions

10. Boyle’s Law A balloon filled with helium gas has a volume of 500 mL at 1.00 atm. When it rises to a higher altitude, the pressure is reduced to 0.50 atm. If the temperature is constant, what is the volume of the balloon? 1000 mL

11. Charles’ Law: V/T relationship Defn – at constant P, volume of fixed amt of gas varies directly with Kelvin temp Directly – as one variable increase, the other increases V T

12. Charles’ Law Formula V 1 & T 1 are initial conditions V 2 & T 2 are final conditions

13. Charles’ Law A helium balloon has a volume of 2.75 L at 20°C. On a cold day, the balloon is placed outside where it shrinks to 2.46 L. What is the temperature outside? 262 K

14. Gay-Lussac’s Law: P/T relationship Defn – at constant V, pressure of fixed amt of gas varies directly with Kelvin temp Directly – as one variable increase, the other increases P T

15. Gay-Lussac’s Law Formula P 1 & T 1 are initial conditions P 2 & T 2 are final conditions

16. Gay-Lussac’s Law Before a trip from Sugar Land to South Padre, the pressure in an automobile tire reads 2.1 atm at 27°C. Upon arriving in Padre, the gauge reads 2.3 atm. What is the temperature in South Padre? 329 K

17. Combined Gas Law: P/T/V Defn – relationship between P,V, & T of fixed amount of gas Formula

18. Combined Gas Law The volume of a gas is 27.5 mL at 22.0°C and 740 mm Hg. What will be its volume at 15°C and 755 mm Hg? 26 mL

19. Avogadro’s Principle Defn – equal volumes of gases at same temp and pressure contain equal number of molecules - the size of the molecule does not influence the volume a gas occupies - for example, 1000 relatively large Kr gas molecules occupies the same volume as 1000 smaller He gas molecules

20. Molar Volume of a Gas Molar Volume – volume that one mole of a gas occupies at STP (0°C, 1 atm) 1 mole = 22.4 L

21. Molar Volume of a Gas Ex prob #1: calculate the volume 0.881 mol H 2 will occupy at STP. 0.881 mol H 2 0.881 mol H 2 x 22.4 L H 2 1 mol H 2 = 19.7 L H 2

22. What is the mass of 0.0752 L of oxygen gas at STP? 0.0752 L O 2 0.0752 L O 2 x 1 mol O 2 22.4 L O 2 0.0752 L O 2 x 1 mol O 2 x 32 g O 2 22.4 L O 2 1 mol O 2 = 0.107 g O 2

23. Ideal Gas Law Defn – relationship between P,V,T and # of moles, n Formula PV = nRT

24. Ideal Gas Law Defn – relationship between P,V,T and # of moles, n Formula PV = nRT ideal gas constant

25. Ideal Gas Constant 3 different R constants R = 0.0821 L·atm mol·K = 62.4 L· mm Hg mol·K = 8.314 L·kPa mol·K pay attention to what unit of pressure is given in problem to use the appropriate R

26. Ideal Gas Law Ex prob 1: what is the volume of 0.250 moles of oxygen gas at 20°C and 740 mm Hg? which R do we use? 6.18 L O 2

27. Ideal Gas Law Ex prob 2: calculate the pressure, in atm, of 4.75 L NO 2 containing 0.86 mol at 27°C. 4.46 atm

28. Ideal Gas Law Ex prob 3: calculate the grams of N 2 present in a 0.600 L sample kept at 1.0 atm and 22°C. first determine # of moles 0.025 mol N 2 convert to grams 0.70 g N 2