Unit 7 Part 5- Gases in Earth's Atmosphere

​Gases in Earth's Atmosphere

Multiple Choice

A rubber tire holds 2.3 moles of CO₂ at a temperature of 273 K. The volume of the tire is 8 L. What is the Pressure?

(R = 0.0821)

• 6.4 atm

• 412.4 atm

• 43.5 atm

• 3.1 atm

Multiple Choice

What does the unit Kelvin, K, measure?

• Pressure

• Volume

• Mass

• Temperature

Multiple Choice

The pressure on a tank containing 0.3 moles of oxygen is 4.5 atm, and the temperature is 150 K. What is the volume of the gas?

(R = 0.0821)

• 0.821 L

• 8.21 L

• 82.1 L

• 821 L

Lesson Objectives

• Describe How Gases interact in Earth's Atmosphere

​Composition of the Atmosphere

• Earth's atmosphere is made up of many different gases

  • The Pressure in the atmosphere is equal to the sum of all the pressures

• The main gases

  • Nitrogen=78.08%

  • Oxygen=20.95%

  • Argon= 0.93%

  • Trace Gases

    • Carbon Dioxide=0.036%

    • Neon=0.0018%

    • Helium=0.0005%

    • Methane=0.00017%

​Dalton's Law

• 1801- John Dalton recognizes that when volume and temperature are constant, the total Pressure is equal to the sum of all the individual pressures

  • P_total=P₁+P₂+P₃+...........​

​Dalton's Law Practice Problem

• Air contains oxygen, nitrogen, argon, and trace amount of other gases. What is the partial pressure of oxygen at 101.30 kPa, 79.10 kPa, 0.94 kPa, and 0.040 kPa respectively?

  • Step 1: Identify knowns

    • P_total=101.30 P_N=79.10, P_Ar=0.94, P_others =0.040​

  • Step 2: Rearrange Dalton's Law

    • P_O=P_total-P_N-P_Ar-P_others

  • Step 3: Substitute your Numbers into the Equation

    • P_O=101.30-79.10-0.94-0.040

Fill in the Blanks

Air contains oxygen, nitrogen, argon, and trace amount of other gases. What is the partial pressure of oxygen at 101.30 kPa, 79.10 kPa, 0.94 kPa, and 0.040 kPa respectively?

Fill in the Blanks

A tank of gas contains 50 kPa of helium, 50 kPa of argon, and 100 kPa of neon. What is the total pressure of the gas mixture?

​Dalton's Law in the atmosphere

• As you ascend a mountain, the Pressure decreases

  • This is due to the amount of Oxygen and Nitrogen Decreasing​

    • The overall ratio remains the same

​Diffusion

• Diffusion: the tendency of molecules to move toward areas of lower concentration until the concentration is uniform

  • Gas Molecules spread out and fill the area evenly

  • Smaller particle move faster

  • Gas expelled at a faster rate results in a faster rate of diffusion​

​Effusion & Graham's Law

• Effusion: the movement of gas inside a container

  • Gas moves through a tiny hole

• Graham's law of Effusion: The rate of effusion of a gas is inversely proportional to the square root of the gas's molar mass (M)

​Comparing Effusion Rates Sample 1

• How much faster does helium (He) effuse than Nitrogen (N₂) at the same temperature?

  • Step 1: Identify the molar mass of both gases

    • He=4.0

    • Ne=28.0​

  • Step 2: Substitute the numbers into Graham's law

Fill in the Blanks

How much faster does helium (He) effuse than Nitrogen (N₂) at the same temperature?

Multiple Choice

Which equation represents Dalton's Law?

• e=mc2
• PV=nRT
• P1/T1=P2/T2
• Ptotal=P1, P2, P3...

Multiple Choice

Earth's current atmosphere is

• 78% nitrogen, 21% oxygen, 0.9% argon and 0.037% carbon dioxide
• 78% oxygen, 21%nitrogen, 0.9% argon, 0.037% carbon dioxide
• 78% nitrogen, 21% argon, 1% oxygen
• 78% oxygen, 21% nitrogen, 1% carbon dioxide