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Chemistry Chapter 18 Notes_ Gases

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Chemistry Chapter 18 Notes_ Gases Powered By Docstoc
					Gases
Chapter 14
         14.1 The Gas Laws
• Kinetic Theory helps us understand the
  behavior of gases:
1st – All gases are made of tiny particles.
2nd – Gas particles are in constant, random
  motion.
3rd – All collisions between
      gas particles are
      perfectly elastic.
In order to study Gases; one must keep track
  the types of units used in each problem.
• Temperature: oC or K.
• Pressure: kPa, mm Hg, Torr. or Atm.
• Volume: mm3, cm3, m3, L, mL.
• In this chapter we are dealing with Ideal
  Gases. Ideal Gas particles do not have a
  volume and no mutual attraction.
STP - Standard Temperature & Pressure.
• Standard Temperature is 0 oC (273 K)
• Standard Pressure is 1 atm (760 mmHg)
              Boyle’s Law

• Boyle’s Law states that at constant
  temperature, the pressure of a gas varies
  inversely with the volume of a gas.


               P1 V 1 = P2 V 2
• EX1:  A gas has a volume 2.0 L and a
  pressure of 1.0 atm, what volume
  will the gas have at 4.0 atm? At
  constant temperature.

• EX2:  A gas has a volume 3 L and a
  pressure of 2.0 atm, what pressure
  will the gas have at 24 L? At
  constant temperature.
• Practice Problem 1: A gas has a
  volume 50.0 L and a pressure of 8.0
  atm, what volume will the gas have at
  10.0 atm?

• Practice Problem 2: A gas has a
  volume 20.0 L and a pressure of 5.0
  atm, what pressure will the gas have at
  25.0 L?
             Charles’ Law
• At constant pressure, the volume of a gas
  varies directly with the temperature of a
  gas.
                  V1 = V2
                  T1 T2

• All temperatures must be in Kelvin (K)
                K = oC + 273
• EX1:  A gas has a volume 24 L and a
  temp of 27.0 °C, what volume will the
  gas have at 127.0 °C ?

• EX2: A gas has a volume 30 L and a
  temp of 77.0 °C, what temp will the gas
  have at 120 L?
• Practice Problem 1: A gas has a volume
  50 L and a temp of 227 °C, what volume
  will the gas have at 127 °C?

• Practice Problem 2: A gas has a volume
  900 cm3 and a temp of 100.0 K, what
  temp will the gas have at 450 cm3?
Gases
Chapter 14
   14.2 The Combined Gas Law &
        Avogadro’s Principle
• The Combined Gas Law joins Boyle’s Law
  with Charles’s Law:

     P1 V 1 = P2 V 2
      T1        T2

• All calculation must be in Kelvin!!!
                       K = oC + 273.
• EX1: A gas at 2.0 atm
  and 27.0 °C fills a
  flexible container with
  an initial volume of 3.0
  L. If the temperature is
  raised to 127.0 °C and
  the pressure is increased
  to 4.0 atm, what is the
  new volume?
• EX2: A helium-filled
  balloon at sea level has a
  volume of 2.0 L at 1.0
  atm and 280 °C. If it is
  released and rises to an
  elevation at which the
  pressure is 1.5 atm and
  the temperature is 27 °C,
  what will be the new
  volume of the balloon?
• Practice Problem 1: At 200 K
  and 1.00 atm pressure, a
  sample of gas occupies 30.0-
  mL. If the temperature is
  increased to 300.0 K and the
  entire gas sample is
  transferred to a 20.0-mL
  container, what will be the
  gas pressure inside the
  container?
• Practice Problem 2: A sample of air in a
  syringe exerts a pressure of 100 kPa at a
  temperature of 27.0 °C. The syringe is
  placed in a warm water bath at 87.0 °C.
  The pressure of the air is
  increased to 120 kPa by
  pushing the plunger in,
  which reduces the
  volume to 0.20 -mL.
  What was the original
  volume of the air?
• Practice Problem 3: An
  unopened, cold 2.00-L bottle of
  soda contains 46.0-mL of gas
  confined at a pressure of 1.30
  atm at a temperature of 5.0 °C.
  If the bottle is dropped into a
  lake and sinks to a depth at
  which the pressure is 1.52 atom
  and the temperature is 2.09 °C,
  what will be the volume of the
  gas in the bottle?
Gases
Chapter 14
           Molar Volume
• Avogadro’s Principle: at equal
  temperatures and equal pressures, equal
  volumes of gases contain the same
  number of molecules.
• 1 mole of any gas equals 22.4 liters at STP.
         Ideal Gas Equation


                PV = nRT

• P = pressure measured in atmospheres (atm)
• V = volume measured in liters (L)
• n = moles measured in moles (mol)
• R = gas constant (0.08 L-atm/mol-K)
• T = temperature measured in Kelvin (K)
• EX1: What pressure is exerted by a gas in a
  propane container with a volume of 2.0 L
  at 200 K and 5.0 mol?
• Practice Problem 1: Find the volume of a
  gas with 10.0 moles at 500 K and 4.0 atm.
• PP2: A typical float at the
  Macy’s Thanksgiving
  Parade has a volume of
  1,800,000-L at 1.0 atm and
  27 °C. Find the number of
  moles of gas in the float.
• PP3: Find the temperature in Celsius for a
  gas held in a 2,000 mL balloon with 5.0
  moles at 1520 torr.
Molecular Mass Determination
                 M = mRT
                      PV
• M = molecular mass in grams/mole
  (g/mol)
• m = mass of sample in grams (g)
• R = gas constant (0.08 L-atm/mol-K)
• T = temperature in Kelvin (K)
• P = pressure in atmospheres (atm)
• V = volume in liters (L)
• EX1: What is the
  molecular mass of
  a gas if 1.00 L has
  a mass of 2.0
  grams at 200 K
  and 4.0 atm.
• PP2: What is the molecular mass of a gas if
  100 grams of it occupies 20.0 L at 5.0 atm
  at 500 K.
•
• PP2: What is the molecular mass of a gas if
  100.0 centigrams of it occupy 200.0 mL at
  380 mmHg and 500 K?
Gases
Chapter 14
            Mass-Volume
• Gas stoichiometry can be used to predict
  the products of a reaction.


        1 mole = 22.4 L at STP
 Stoichiometry Solving Process
• Find the balanced equation for the
  reaction.
• Convert given amount to moles.
• Use mole ratio to find moles of desired
  particle.
• Convert moles of desired particle to
  correct unit.
 Mass-Volume Stoichiometry
EX1: How many liters of ammonia are
produced by the reaction of 56.0-grams of
nitrogen gas (N2) with excess hydrogen
gas (H2)?

          N2(g) + 3 H2(g) à 2 NH3(g)
• Practice Problem 1: How many liters of
  water vapor (H2O) are created by the
  decomposition of 400-grams of
  ammonium nitrate (NH4NO3)?

    NH4NO3(s) à N2O(g) + 2 H2O (g)
• Practice Problem 2: How many liters of
  chlorine gas (Cl2) are needed to
  completely react with 276 grams of solid
  sodium (Na)?

          2 Na (s) + Cl2 (g) à 2 NaCl (s)
  Volume-Mass Stoichiometry
• EX2: Find the mass of water that is
  produced by the reaction of 67.2-L of
  oxygen gas (O2) with excess hydrogen gas
  (H2) at STP.
           H2 (g) + O2 (g) à H2O (l)
• Practice Problem 3: Calculate the mass of
  hydrogen gas (H2)needed to react with 224
  -L of nitrogen gas (N2) at STP.

       N2 (g) + 3 H2 (g) à 2 NH3 (g)
• Practice Problem 4: Calculate the mass of
  carbon dioxide (CO2) produced by the
  reaction of 1120-L of propane (C3H8) at
  STP.

   C3H8 + 5 O2 (g) à 3 CO2 (g) + 4 H2O (l)
Volume-Volume Problems

• EX3: How many liters of carbon dioxide
  (CO2) are produced by the reaction of
  11.2-L of propane (C3H8)?

C3H8 (g) + 5O2 (g) à
 3CO2 (g) + 4H2O (l)
• Practice Problem 5: How many liters of
  carbon dioxide (CO2) are produced by the
  reaction of 448-L of oxygen gas (O2)?

 C3H8 (g) + 5 O2 (g) à 3 CO2 (g) + 4 H2O (l)

				
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posted:4/29/2014
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