Warmup: 1. The volume of a gas is 27. 5 mL at 22. 0°C and 0. 974 atm Warmup: 1. The volume of a gas is 27.5 mL at 22.0°C and 0.974 atm. What will the volume be at 15.0°C and 0.993 atm? 2. Suppose that 120. mL of argon is collected over water at 25°C with an atmospheric pressure of 780 mmHg. Compute the volume that this argon gas would occupy at STP instead.

V1 T1 P1 1. The volume of a gas is 27.5 mL at 22.0°C and 0.974 atm. What will the volume be at 15.0°C and 0.993 atm? P2 T2 V2 Initial After P1 = P2 = V1 = V2 = T1 = T2 = 0.974 atm 0.993 atm V2 = 27.5 mL ? 22°C 295 K 15°C 288 K V2 = 26.3 mL

Initial Final Ptotal = PAr + PH2O 780mmHg = PAr + 23.8mmHg 2. Suppose that 120. mL of argon is collected over water at 25°C with an atmospheric pressure of 780 mmHg Compute the volume that this argon gas would occupy at STP instead. Part 1: What is the pressure of argon INITIALLY? Part 2: What is the volume AFTER I change the conditions? Initial Final P1 = P2 = V1 = V2 = T1 = T2 = Ptotal = PAr + PH2O 780mmHg = PAr + 23.8mmHg PAr = 756 mmHg 756 mmHg 760 mmHg ? 120 mL 298 K 273K Answer: 109 mL

The Ideal Gas Law

Universal Gas Constant The Ideal Gas Law relates pressure, volume, temperature, and moles of a gas : PV = nRT Temperature of Gas (in Kelvin) Pressure of Gas (in atm) Universal Gas Constant Volume of Gas (in L) Moles of Gas (in moles)

1. What is the pressure in atmospheres exerted by a 5 1. What is the pressure in atmospheres exerted by a 5.00 mol sample of N2 in a 10.0 L container at 298K? PV = nRT P V n R T ? 10.0 L 5.00 mol P = 12.2 atm 298 K

? 9.22 L 0.125 mol 298 K P V n R T PV = nRT P = 0.332 atm P = 33.6 kPa 2. What pressure (in kPa) will be exerted by 0.125 moles of neon gas contained in a 9.22 L vessel at 25.0°C? PV = nRT P V n R T ? 9.22 L 0.125 mol 298 K P = 0.332 atm Hint: 1 atm = 101.3 kPa P = 33.6 kPa

3. How many grams are contained in 5.00 L of chlorine gas at STP? PV = nRT P V n R T 1.00 atm 5.00 L 70.9 g Cl2 0.223 mol Cl2 ? 1 mol Cl2 273 K 15.8 g Cl2

4. C2H4(l) + 2O2(g)  2CO2(g) + 2H2O(g) A 6.82 x 10-3 mole sample of ethene goes through complete combustion, producing carbon dioxide gas in a 250. mL container at 400 K. What is the pressure exerted by the gas? 250 mL  ? L P V n R T ? 2 6.82x10-3 mole C2H4 mol CO2 = 1.36 x 10-2 moles CO2 0.250 L 1 mole C2H4 0.0136 mol P = (1.36 x 10-2)(0.0821)(400) 0.250 400 K 2 atm

5. A 32. 5 gram sample of an unknown diatomic gas was placed in a 250 5. A 32.5 gram sample of an unknown diatomic gas was placed in a 250. mL container at 400. K and 60.2 atm. What is the molar mass, and identity of this gas? PV = nRT P V n R T 60.2 atm molar mass = g/mole 0.250 L (60.2)(0.250) = n(o.0821)(400.) ? n = 0.458 moles molar mass = 32.5 g/0.458mole 400 K 71 g/mole 71 / 2 diatomic = 35.5 = Cl2

R lab! Stuff to think about: 1. This is a gas lab. Vinegar and baking soda aren’t gases. What? 2. What are we trying to DO? I know this is an experiment with lots of steps and stuff, but what are we trying to PROVE? 3. How will you collect data for each variable (P,V,n,T)? Specifically? 4. Why did I give you a balloon? 5. Which chemical will be the limiting reactant in your reaction? 6. How important is it that all of your baking soda is used up in the reaction? What about the vinegar? 7.How do you KNOW that your yield is enough? 8. How do you KNOW that your R value is accurate? 9. Barometric pressure on the website is in inches of Hg, you must convert!