Lab Dates. CRHS Academic Chemistry Unit 11 Gas Laws Notes

Transcription

1 Name Period CRHS Academic Chemistry Unit 11 Gas Laws Notes Quiz Date Lab Dates Exam Date Notes, Homework, Exam Reviews and Their KEYS located on CRHS Academic Chemistry Website:

2 Page 2 of 12 Unit 10 Notes 11.1 GAS PROPERTIES In Chemistry, we will consider ALL GASES to be. Q: What is an ideal gas? An ideal gas is any gas that meets the 5 basic assumptions of theory stating how the particles of any move. The 5 Basic Assumptions: 1. Gas particles do not or each other. 2. Gas particles are much than the distances between them. a. almost all the volume is b. explains high compressibility 3. Gas particles are in motion. a. particles move in until collision b. explains why gases any container 4. No energy is lost when gas particles collide with each other or the walls of their container. 5. All gases have the average kinetic energy at a given. Gases and Increasing Temperature When gases are heated, kinetic energy.. When a gas has kinetic energy, its particles push harder on the container or surroundings. If the container can expand, the gas will increase. o A rubber balloon If the container cannot expand, gas will increase. o A rigid container, like a glass jar. Avogadro s Law two different gases of equal volume at the pressure and temperature have equal numbers of, and, regardless of the identity of either gas. So, gas particles, when under the same sets of physical conditions, will all behave the same way.

3 Unit 10 Notes Page 3 of 12 We learned in the stoichiometry unit that 1 mole of ANY gas at standard temperature and pressure contains L of gas. Dalton s Law of Partial Pressures In a of gases, the pressure exerted by the mixture of gases is equal to the of the partial pressure of each gas. P total = P Gas 1 + P Gas 2 + P Gas3 Example Air contains N 2, O 2, H 2O, Ar, CO 2, the sum of which makes up the air pressure around us at any time. At sea level, the air pressure is kpa, but air is not a pure gas, it is a mixture of the above gases along with a few other trace gases. N 2 + O 2 + H 2 O + Ar + CO 2 = Air 78.1 kpa kPa kPa kPa kPa = 101.3kPa

4 Page 4 of 12 Unit 10 Notes 11.2 IDEAL GAS LAW 1. Pressure ( ) created by the molecules of gas with the walls of the container Standard International Unit, or unit, is the, kpa. Standard pressure = kilopascals kilopascals = atmosphere = mm Hg Practice: Convert 1.4 atmospheres of pressure to kpa. 2. Temperature ( ) a measure of the energy of gas particles temperature is proportional to kinetic energy SI unit is (K) NO degree symbol! ALL calculations in this unit are in KELVIN To convert from Celsius, K = Standard temperature = K = C 0 K is called zero, the temperature at which the motion of particles theoretically. Practice: Convert 33 Celsius to Kelvin. 3. Volume ( ) the 3-D space enclosed by the a container s SI unit is (L) At standard temperature and pressure (STP), there are of a gas per one mole of that gas.

5 4. Number of Moles ( ) Unit 10 Notes Page 5 of 12 of gas present, in if amount is given in grams, we will to moles STP = standard temperature and pressure o Temperature: 0 C = 273K o Pressure: 101.3kPa = 1 atm = 760 mmhg We can use the that describe a gas to find unknown properties of an gas. Remember Pressure (P) Temperature (T) Volume (V) Moles (n) All calculations are done using KELVIN temperatures! Q: What is R? R is the ideal gas. There are ideal gas constants for pressure in kpa, atm, and mmhg.. pressure in kilopascals R = 8.31 L kpa mol K pressure in atmospheres R = L atm mol K pressure in mm Mercury R = 62.4 L mmhg mol K Example 1 When the temperature of a hollow sphere with 685 L (volume) of helium gas is held at 621 K (temperature), the pressure of the gas is 1.89 x 10 3 kpa. How many moles of helium does the sphere contain?

6 Page 6 of 12 Unit 10 Notes Example 2 What pressure in kpa will be exerted by mole of a gas at 25 C if it is held in a 0.650L container? Example 3 What volume will 2.50 mol of nitrogen gas occupy at STP (0 C and 1 atm of pressure)? Example 4 What volume will 12.0 grams of oxygen gas occupy at 25 C and a pressure of atm? Hint 1: HOFBrINCl Hint 2: convert grams to moles

7 11.3 COMBINED GAS LAWS AND BOYLES LAW Unit 10 Notes Page 7 of 12 Combined Gas Law - states the relationship among pressure, volume, and temperature of a fixed amount of a gas under sets of conditions. We are given 5 of 6 values, so we can calculate the missing value. We MUST use Kelvin for temperature Example 1 A gas at 155 kpa and 25.0C occupies a container with an initial volume of 1.00 L. By changing the volume, the pressure of the gas increases to 605 kpa as the temperature is raised to 125C. What is the new volume? Practice 1 A 5.00 L air sample at a temperature of 50.0C has a pressure of atm. What will be the new pressure if the temperature is raised to 102C and the volume expands to 7.00 L? Practice 2 A L sample of air has a pressure of kpa. What volume will it occupy at kpa if the temperature is held constant at 273 K?

8 Page 8 of 12 Unit 10 Notes Q: What is Boyle s Law? Boyle s Law - is held constant. As pressure, volume. As pressure, volume. relationship Record your observations from the class demonstration below. Example 1 - A high altitude balloon contains 30 L of helium gas at 103 kpa. What is the volume when the balloon rises to an altitude where the pressure is only 25 kpa? (Assume that temperature remains constant.) Practice 1 - A tank of nitrogen has a volume of 14.0 L and a pressure of 1.0 atm. Find the volume of the nitrogen when the pressure is increased to 2.1 atm while the temperature is held constant. Practice 2 - The volume of the lungs is measured by the volume of air inhaled or exhaled. If the volume of the lungs is 2.40 L during exhalation and the pressure is KPa, and the pressure during inhalation is kpa, what is the volume of the lungs during inhalation? Temperature is constant.

9 11.4 CHARLES AND GAY LUSSAC LAW Q: What is Charles s Law? Unit 10 Notes Page 9 of 12 Charles s Law Charles s Law - is held constant. As temperature, volume. As temperature, volume. relationship Record your observations from the class demonstration below. Example 1 - A balloon inflated in a room at 24 C has a volume of 4.0 L. The balloon is then heated to a temperature of 58 C. What is the new volume if the pressure is held constant? Practice 1 - If 15.0 liters of neon gas at 25 C is allowed to expand to 45.0 liters, what must the new temperature be to maintain constant pressure? Practice 2 A 600L sample of oxygen gas is stored in a flexible container at 15 C. It is suddenly heated to 42 C. What will the new volume be, assuming pressure is unchanged?

10 Page 10 of 12 Q: What is Gay-Lussac s Law? Unit 10 Notes Gay-Lussac s Law Gay-Lussac s Law - is held constant. As temperature, pressure. As temperature, pressure. relationship Record your observations from the class demonstration below. Example 1 - The gas left in a used aerosol can is at a pressure of 103 kpa at 25 C. If this can is thrown into a fire, what is the pressure of the gas when its temperature reaches 928 C? Practice 1 - If a gas in a closed container is pressurized from 15.0 atm to 16.0 atm and its original temperature was 25 C, what would the final temperature of the gas be? Practice 2 A solid, sealed steel container full of carbon dioxide gas is being heated from a starting temperature of 22 C. The final temperature is 635 C and the final pressure is 431 kpa. What was the original pressure of gas inside the container?

11 Dalton s Law P Total = P 1 + P 2 + P 3 Unit 10 Notes Page 11 of 12 Ideal Gas Law PV = nrt Combined Gas Law P 1 V 1 T 1 = P 2V 2 T 2 Boyle s Law P 1 V 1 = P 2 V 2 Charles s Law V 1 T 1 = V 2 T 2 Gay-Lussac s Law P 1 T 1 = P 2 T 2 STP Temperature: 273K = 0 C Pressure: kpa = 1.0 atm = 760 mmhg K = C + 273

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