Transcript The Gas Laws - iss.k12.nc.us

Chapter 14
Chemistry
Remember gases behave
differently
Gases are affected by
Temperature
Pressure
Volume
Boyle’s Law
 Robert Boyle
 Relationship between pressure and volume
 P1V1 = P2V2
 Inverse relationship – As volume decreases, pressure
increases
Example Problem
 A 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 Law
 Jacques Charles
 Relationship between temperature and pressure
 Direct Relationship
 V1 = V2
T1
T2
Sample Problem
 A 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 Activity
 Cold Balloon
 Bottle Crush
 Popcorn
Gay-Lussac’s Law
 Relationship between temperature and pressure
 Volume must be held constant
 Direct relationship
 P1 = P2
T1
T2
Sample Problem
 The 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 Problem
 A 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 Principle
 Equal 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 Problem
 Calculate the volume that 2.0 Kg of methane gas
(CH4) will occupy at STP
Ideal Gas Law
 Ideal 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
Practice
 Calculate 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 = nRT
P = 1.5 atm
V = 3.0L
R = .0821
T = 3oo K
N=?
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 problem
 What 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
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
1.
Volume to Mass Problem
 Ammonia 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 unknown
 Determine volume ratio
 Use ratio to determine liters of ammonia produced
 Rearrange 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