1. 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 atm. What will the volume be at 15.0°C and 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.

2. V1 T1 P1
1. The volume of a gas is mL at °C and atm. What will the volume be at °C and 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

3. 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 mmHg
PAr = 756 mmHg
756 mmHg
760 mmHg ?
120 mL
298 K
273K
Answer: 109 mL

4. The Ideal Gas Law

5. 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)

6. 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 = atm
298 K

7. ? 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 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 = atm
Hint: 1 atm = kPa
P = kPa

8. 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

9. 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
mol
P = (1.36 x 10-2)(0.0821)(400)
0.250
400 K
2 atm

10. 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 = moles
molar mass = 32.5 g/0.458mole
400 K
71 g/mole
71 / 2 diatomic = 35.5 = Cl2

11. 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!