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Turn in your Homework. Gases. Chapters 12.1 and 13. Gases. Chemistry- Matter and Change: 12.1. 12.1 Main Idea. Gases expand, diffuse, exert pressure, and can be compressed because they are in a low-density state consisting of tiny, constantly moving particles. Objectives.
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Gases Chapters 12.1 and 13
Gases Chemistry- Matter and Change: 12.1
12.1 Main Idea Gases expand, diffuse, exert pressure, and can be compressed because they are in a low-density state consisting of tiny, constantly moving particles
Objectives • Predict the behavior of gases using the kinetic-molecular theory • Explain how mass affects the rates of diffusion and effusion • Measure gas pressure • Calculate effusion rates
Review Vocabulary • Kinetic energy • Molar mass
New Vocabulary • Kinetic-molecular theory • Elastic collision • Temperature • Diffusion • Graham’s Law • Pressure • Barometer • Manometer • Pascal (Pa) • Atmosphere (atm)
Kinetic Energy • The energy an object has because of its motion is called kinetic energy. • According to the kinetic theory, all matter consists of tiny particles that are in constant motion.
Kinetic-Molecular (KM) Theory • Assumptions • Particle size is very small • Particles take up relatively no space • Particles are far apart • Very little interaction of particles • Collisions are elastic • No kinetic energy is lost in a collision
Behavior of Gases: Temperature • Determined by mass and velocity • Temperature- the average kinetic energy of particles in matter
Absolute zero • Theoretical point at which all molecular motion stops. • 0 K; -273.15 °C; −459.67° F
Behavior of Gases: Pressure • Pressure- the result of simultaneous collisions of billions of rapidly moving particles in a gas with an object.
Pressure • Pressure (P) is defined as the force per unit area on a surface. (P=F/A) • Gas pressure is caused by collisions of the gas molecules with each other and with surfaces with which they come into contact. • The pressure exerted by a gas depends on volume, temperature, and the number of molecules present. • The greater the number of collisions of gas molecules, the higher the pressure will be.
Gas Pressure • Units • Pascal (1 Pa = N /m2) • *Atmosphere (1 atm = 101.3 kPa) • *mm Hg (1 atm = 760 mm Hg) • *Torr (1 torr = 1 mm Hg)
Gas Pressure Barometer Manometer Manometers measure gas pressure in a closed system • Barometers measure atmospheric pressure • open system
Behavior of Gases: Volume • Compression and expansion- density of material can be changed by changing the available volume
Behavior of Gases: Motion • Diffusion- movement of one material through another • Concentration gradient • Effusion- gas escaping from a confined space through tiny openings
What is the ratio of the rate of diffusion for ammonia and hydrogen chloride?
Calculate the ratio of effusion rates for nitrogen gas and neon • RN/RNe=0.849
Can you… • Predict the behavior of gases using the kinetic-molecular theory • Explain how mass affects the rates of diffusion and effusion • Measure gas pressure
Homework • Packet pg 3-4 and 10 • Textbook pg 405 (1-3) pg 409 (4-7)
The Gas Laws Chapter 13.1
13.1 Main Idea For a fixed amount of gas, a change in one variable- pressure, volume or temperature- affects the other two.
13.1 Objectives • Calculate the partial pressure of a gas • State the relationships among pressure, volume, temperature, and the amount of gas • Apply gas laws to problems involving pressure, volume, temperature, and the amount of gas • Create graphs of the relationships among pressure, volume, temperature, and the amount of gas • Solve problems related to fixed amounts of gases
Review Vocabulary • Scientific law • Directly related • Indirectly (inversely) related • Kelvin
New Vocabulary • Ideal gas • Absolute zero • Dalton's law of partial pressure • Boyle’s law • Charles’s law • Gay-Lussac’s law • Combined gas law
Dalton’s Law of Partial Pressures • total pressure is the sum of the partial pressures • Ptot=P1 + P2 + P3 + … Pn
A mixture of O2, CO2 and N2 has a total pressure of 0.97 atm. What is the partial pressure of O2 if the partial pressure of CO2 is 0.70 atm and the partial pressure of N2 is 0.12 atm? • 0.97 atm = 0.70 atm + 0.12 atm + x • X = 0.15 atm
Ideal gases • Non-existent, but assumes the following: • Completely elastic collisions • Particles occupy no volume • Large number of particles • No attractive or repellent forces between particles • Molecules are in completely random motion
Boyle’s Law • Constants: amount of gas (n) and temperature (T) • Boyle's Law in Motion
A diver blows a 0.75 L air bubble 10 m under water. As it rises, the pressure goes from 2.25 atm to 1.03 atm. What is the volume of the bubble at the surface? • P1V1=P2V2 2.25 atm 0.75 L = 1.6 L 1.03 atm
A sample of oxygen gas has a volume of 150.0 mL when its pressure is 0.947 atm. What will the volume of the gas be at a pressure of 0.987 atm if the temperature remains constant? • Given:V1 of O2 = 150.0 mL • P1 of O2 = 0.947 atm • P2of O2= 0.987 atm • Unknown:V2of O2in mL • Solution: • Rearrange the equation for Boyle’s law (P1V1 = P2V2) to obtain V2.
Charles’s Law • Constants: amount of gas (n) and pressure (P) • Temperature is in Kelvin (K) • K= C + 273.0 • Charles' Law in Motion
A helium balloon in a closed car occupies a volume or 2.32 L at 40°C.If the temperature rises to 75°C, what is the new volume of the balloon? • V2=V1T2/T1 348.0 K 2.32 L = 2.58 L 313.0 K
A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant?
Given:V1 of Ne = 752 mL • T1 of Ne = 25°C + 273 = 298 K • T2of Ne = 50°C + 273 = 323 K • Unknown:V2of Nein mL • Solution: • Rearrange the equation for Charles’s law to obtain V2.
Gay-Lussac’s Law • Constants: amount of gas (n) and volume (V) • T must be in Kelvin • Gay-Lussac in Motion
The pressure of oxygen gas inside a canister is 5.00 atm at 25°C. the canister is placed in a cold environment where the temperature is -10°C; what is the new pressure in the canister? • P2=P1T2/T1 263.0 K 5.00 atm = 4.41 atm 298.0 K
The gas in a container is at a pressure of 3.00 atm at 25°C. Directions on the container warn the user not to keep it in a place where the temperature exceeds 52°C. What would the gas pressure in the container be at 52°C?
Given:P1 of gas = 3.00 atm • T1 of gas = 25°C + 273 = 298 K • T2of gas = 52°C + 273 = 325 K • Unknown:P2of gasin atm • Solution: • Rearrange the equation for Gay-Lussac’s law to obtain P2.
Predict • The relationship between pressure and amount of gas at a fixed temperature and volume • Pressure-Moles relationship • The relationship between volume and the amount of gas at a fixed temperature and amount of gas • Volume-Moles relationship
Combined Gas Law • Combination of Boyle’s, Charles’, and Gay-Lussac’s laws