Gases Part 2: Boyle's Law and Charles's Law

Gases Part 2: Boyle's Law and Charles's Law

By Abby Fancsali

Introduction​

• The Gas Laws are a set of mathematical relationships between

  • volume

  • temperature

  • pressure

  • amount of gas​

Section 1: Boyle's Law​

• Robert Boyle found that doubling the pressure on a sample reduced the volume of a gas by half

  • A smaller area means gas molecules have less room and are more likely to bump into one another

• Mathematically shown:

  • P ×​ V = k

    • k is a constant

  • P₁ × V₁ = P₂ × V₂

    • The units do not matter as long as they are the same on both sides of the equation!

Section 1: Boyle's Law​ Sample Problem 1

• 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 0.987 atm if the volume of the gas remains constant?

  • Identify what we have

    • V₁= 150

    • P₁=0.947

    • V₂ = ?

    • P₂ =0.987

  • Plug our Values into Boyle's Law

    • 150 x 0.947 = V₂ x 0.987 ​

Fill in the Blanks

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 0.987 atm if the Temperature of the gas remains constant? Round to 2 Decimal places

Section 1: Boyle's Law​ Sample Problem 2

• A helium ballon contains 125 mL of gas at a pressure of 0.974 atm. What Volume will the gas occupy at STP (1 atm)?

  • Identify what we have

    • V₁= 125

    • P₁=0.974

    • V₂ = ?

    • P₂ =1

  • Plug our Values into Boyle's Law

    • 125 x 0.974 = V₂ x 1 ​

Fill in the Blanks

A helium ballon contains 125 mL of gas at a pressure of 0.974 atm. What Volume will the gas occupy at STP (1 atm)? Round to 2 Decimal Places

Section 1: Boyle's Law​ Sample Problem 3

• Use Boyle's Law to solve for the missing value

  • V₁= 2 x 10⁵ L

  • P₁=?

  • V₂ = 1.8 x 10³

  • P₂ = 180 mm Hg

• Plug our Values into Boyle's Law

  • (2 x 10⁵) x P₁ = (1.8 x 10³) x 180 ​

Fill in the Blanks

Use Boyle's Law to solve for the missing value

V₁= 2 x 10⁵ L, P₁=? V₂ = 1.8 x 10^3, and P₂ = 180 mm Hg Round to 2 Decimal Places

Fill in the Blanks

A Balloon Filled with Helium gas has a volume of 500 mL at a pressure of 1 atm. The balloon is released and reaches an altitude where the pressure is 0.5 atm. If the temperature has remained the same, what volume does the gas occupy at this height?

The Kelvin Temperature Scale

• The Kelvin Temperature scale is used in Charles's Law

  • Convert from Celsius by adding 273 to your temperature

    • 0 ° C = 273 K

    • 100 ° C = 373 K

Fill in the Blanks

What is the temperature of 15 Degrees Celsius in Kelvin?

Section 2: Charles's Law

• Charles's Law looks at how Temperature affects a gas

  • When the pressure is constant, an increase in temperature also increases the volume

    • All Gases expand to the same extent when heated by the same temperature interval​

  • Mathematically: V/T = k

    • For changes:

Section 2: Charles's Law Sample Problem 1

• A Sample of neon Gas occupies a volume of 752 mL at 25° C. What will the Volume be at 50° C if the pressure remains constant?

  • Step 1: Identify what we know

    • V₁= 752 mL

    • T₁= 25°​C

    • V₂=?

    • T₂= 50°C

  • Step 2 Change Temperatures to Kelvin

    • T₁= 25 + 273

    • T₂= 50 + 273

Fill in the Blanks

What is our initial Temperature in Kelvin?

Fill in the Blanks

What is our final Temperature in Kelvin?

Section 2: Charles's Law Sample Problem 1

• A Sample of neon Gas occupies a volume of 752 mL at 25° C. What will the Volume be at 50° C if the pressure remains constant?

  • what we know

    • V₁= 752 mL

    • T₁= 298°​C

    • V₂=?

    • T₂= 323°C

  • Step 3: Plug Values into our Equation and solve for our unknown

Fill in the Blanks

A Sample of neon Gas occupies a volume of 752 mL at 25° C. What will the Volume be at 50° C if the pressure remains constant? **Round to Two Decimal Places**

Section 2: Charles's Law Sample Problem 2

• A balloon filled with Oxygen gas occupies a volume of 5.5 L at 25°C. What Volume will the balloon be at 100°C?

  • what we know°

    • V₁= 5.5 L

    • T₁= 25°​C + 273 = 298

    • V₂=?

    • T₂= 100°C+273 =373 K

  • Step 3: Plug Values into our Equation and solve for our unknown

Fill in the Blanks

A balloon filled with Oxygen gas occupies a volume of 5.5 L at 25°C. What Volume will the balloon be at 100°C? **Round to 2 Decimal Places**