Chapter 14 Chemistry. Remember gases behave differently.
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Transcript of Chapter 14 Chemistry. Remember gases behave differently.
The Gas LawsChapter 14
Chemistry
Remember gases behave differently
Gases are affected byTemperature
Pressure
Volume
Boyle’s LawRobert BoyleRelationship between pressure and volumeP1V1 = P2V2
Inverse relationship – As volume decreases, pressure increases
Example ProblemA sample of helium gas in a balloon is compressed from 4.0 L to 2.5 L at a constant temperature. If the pressure of the gas in the 4.0 L volume is 210 kPa, what will the pressure be at 2.5 L?
P1V1 = P2V2
Boyle’s Law Activity
Marshmallow in Syringe
Dalton’s Law of Partial Pressures
Charles’s LawJacques Charles
Relationship between temperature and pressure
Direct Relationship
V1 = V2 T1 T2
Sample ProblemA gas sample at 40.0oC occupies a volume of
2.32 L. If the temperature is raised to 75oC, what will the volume be, assuming the pressure remains constant?
Charles’s Law ActivityCold Balloon
Bottle Crush
Popcorn
Gay-Lussac’s LawRelationship between temperature and
pressure
Volume must be held constant
Direct relationship
P1 = P2 T1 T2
Sample ProblemThe pressure of a gas in a tank is 3.2 atm at
22.o oC. If the temperature rises to 60 oC, what will be the gas pressure in the tank?
Combined Gas Law
P1V1 = P2V2 T1 T2
Sample ProblemA gas at 110 kPa and 30.o oC fills a flexible
container with an initial volume of 2.oL . If the temperature is raised to 80oC and the pressure increased to 440 kPa, what is the new volume?
Avagadro’s PrincipleEqual volumes of gases at the same
temperature and pressure contain equal numbers of particles
Molar volume = the volume one mole of gas occupies at 0oC and 1.0 atm pressure
One mole of any gas will occupy 22.4L
Practice ProblemCalculate the volume that 2.0 Kg of methane
gas (CH4) will occupy at STP
Ideal Gas LawIdeal gases have almost no volume and the
particles are far enough apart to not exert any type of repulsive or attractive force on another particle.
Do not exist in real world, but most gases behave like ideal gases at STP
PV=nRT
PracticeCalculate the number of moles of gas
contained in a 3.0L vessel at 3.00 x 102 K with a pressure of 1.5 atm
PV = nRTP = 1.5 atmV = 3.0LR = .0821T = 3oo KN = ?
Gas Stoichiometry
Remember, coefficients represent the number of moles of a reactant or product
2 C4H10 + 13 O2 8 CO2 + 10 H2O
Calculations involving only volume
CH4 + 2 O2 CO2 + 2H2O
It takes 2 liters of oxygen to react with 1 L of methane to produce 1 liter of carbon dioxide and 2 liters of water
Volume to volume problemWhat volume of oxygen gas is needed for the
complete combustion of 4.0 L of propane gas (C3H8)? Assume constant pressure and temperature.
C3H8 + 5O2 3CO2 + 4H2O
1. Start with what you know: 4.0L C3H8
2. What is the ratio of Oxygen to propane? 5 oxygen 1 propane
3. Multiply the amount of propane by the ratio to get oxygen 5 x 4 = 20 L
Volume to Mass ProblemAmmonia is synthesized from hydrogen and
nitrogen gases. N2 + 3H2 2 NH3
If 5.00 L of nitrogen reacts completely by this reaction at a constant pressure and temperature of 3.00atm and 298K, how many grams of ammonia are produced?
1. Analyze problem (V, P, T, )
2. Solve for unknownDetermine volume ratioUse ratio to determine liters of ammonia
producedRearrange and use ideal gas law to solve for n
(use liters of ammonia produced as V)3. Convert moles of ammonia to grams of
ammonia