gases (part 3). gas laws a quick review of what we’ve learned
TRANSCRIPT
GASESGASES(Part 3)(Part 3)
Gas Laws
A Quick Review Of What We’ve Learned
Boyle’s LawBoyle’s LawP P αα 1/V 1/VThis means Pressure This means Pressure
and Volume are and Volume are INVERSELY INVERSELY PROPORTIONAL PROPORTIONAL if if moles and moles and temperature are temperature are constant. For constant. For example, P goes up example, P goes up as V goes down.as V goes down.
PP11VV11 = P = P22 V V22
Robert Boyle (1627-1691). Son of Earl of Cork, Ireland..
Nice lipstick, dude!
Charles’s Charles’s LawLaw
If n and P are If n and P are constant, constant, then V then V αα T T
V and T are directly V and T are directly proportional.proportional.
VV11 V V22
==
TT11 T T22
• If one temperature If one temperature
goes up, the goes up, the volume goes up!volume goes up!
Jacques Charles (1746-Jacques Charles (1746-1823). Isolated boron and 1823). Isolated boron and studied gases. Balloonist.studied gases. Balloonist.
Somebody’s got a case of the Mondays
Gay-Lussac’s LawGay-Lussac’s Law
If n and V are constant,
then P α TP and T are directly
proportional.P1 P2
=
T1 T2
• If one temperature goes up, the pressure goes up!
Joseph Louis Gay-Joseph Louis Gay-Lussac (1778-1850)Lussac (1778-1850)
Balloons make me Happy!
Combined Gas Law
If you should only need one of the other gas laws, you can cover up the item that is constant and you will get that gas law!
Boyle’s Law
Charles’ Law
Gay-Lussac’s Law
=P1 V1
T1
P2 V2
T2
IDEAL GAS LAWIDEAL GAS LAW
Brings together gas properties.
BE SURE YOU KNOW THIS EQUATION!
P V = n R TP V = n R T
Gases in the AirThe % of gases in air Partial pressure (STP)
78.08% N2 593.4 mm Hg
20.95% O2 159.2 mm Hg
0.94% Ar 7.1 mm Hg
0.03% CO2 0.2 mm Hg
PAIR = PN + PO + PAr + PCO = 760 mm Hg 2 2 2
Total Pressure 760 mm Hg
Dalton’s Law of Partial Dalton’s Law of Partial PressuresPressures
What is the total pressure in the flask?What is the total pressure in the flask?
PPtotaltotal in gas mixture = P in gas mixture = PAA + P + PBB + ... + ...Therefore, Therefore, PPtotaltotal = P = PHH22OO + P + POO22
= 0.48 atm = 0.48 atm
Dalton’s Law: total P is sum of Dalton’s Law: total P is sum of PARTIALPARTIAL pressures. pressures.
2 H2 H22OO2 2 (l) ---> 2 H(l) ---> 2 H22O (g) + OO (g) + O2 2 (g)(g)
0.32 atm 0.32 atm 0.16 atm 0.16 atm
Dalton’s Dalton’s LawLaw
John DaltonJohn Dalton1766-18441766-1844
Gases and StoichiometryGases and Stoichiometry
2 H2O2 (l) ---> 2 H2O (g) + O2 (g)
Decompose 1.1 g of H2O2 in a flask with a volume of 2.50 L. What is the volume of O2 at STP?
Solve a gas law stoichiometry problem just like any other stoichiometry problem…the unit you want to go to goes on top…the unit you want to get rid of goes on bottom.
Gases and Gases and StoichiometryStoichiometry
2 H2 H22OO2 2 (l) ---> 2 H(l) ---> 2 H22O (g) + OO (g) + O2 2 (g)(g)
Decompose 1.1 g of HDecompose 1.1 g of H22OO22 in a flask with a volume of 2.50 L. What is the in a flask with a volume of 2.50 L. What is the volume of Ovolume of O22 at STP? at STP?
SolutionSolution1.1 g1.1 g HH22OO22 1 mol H 1 mol H22OO22 1 mol O 1 mol O22 22.4 L O 22.4 L O22
34 g H34 g H22OO22 2 mol H 2 mol H22OO22 1 mol O 1 mol O22
= 0.36 L O2 at STP
Gas Stoichiometry: Practice!
A. What is the volume at STP of 4.00 g of CH4?
4.00 g CH4 x 1 mole CH4 x 22.4 L = 5.58 L
16.05g CH4 1 mole
B. How many grams of He are present in 8.0 L of gas at STP?
8.0 L He x 1 mole x 4.00g He = 1.4 g He
22.4 L 1 mole He
Gases and Stoichiometry Gases and Stoichiometry (cont.)(cont.)
• If the problem IS NOT IS NOT at STPSTP…1.Do an A to B stoichiometry problem solving
for moles of the “B” compound2.Use PV = nRT to solve for the variable