Chapter Combined Gas Law and Ideal Gases

Combined Gas Law Equation V 1 x P 1 = V 2 x P 2 T 1 T 2 T 1 T 2 Solve for T 2, V 2, or P 2

The volume of a gas filled balloon is 30.0 L at 313 K and 153 kPa. What would be the volume at STP? Hint: What is P, T at STP? V 1 = 30.0LV 2 =? T 1 =313 KT 2 =273K P 1 =153 kPaP 2 =101.3kPa V 2 =P 1 x V 1 x T 2 =153x30.0x273 = 39.5L P 2 x T x 313 P 2 x T x 313

Ideal Gas Law  Combined gas laws plus n = number of moles R = ideal gas constant, 8.31 (L kPa/K mol) is given to you in tests…. PV = nRT Solve for n=

An underground cavern contains 2,356 L methane gas CH4 at a pressure of 150 kPa and a temperature of 315 K. How many moles of CH 4 does the cavern contain?  P = 150 kPa  V = 2,356 L  T = 315 K  R = 8.13 L kPa/K mol n = 150 x 2,356 n = 150 x 2,356 = 135 moles 8.13 x 315

Real gases behave differently from ideal gases Because real gas particles…  have a volume.  are attracted to each other, especially if compressed.  Turn into a liquid when pressure is high enough or temperature is low enough.

 Portions below curve due to intramolecular attractions  Portions above curve due to particles having a volume

Gas Laws and Diving  Air contains 70% nitrogen  Due to high pressure under water, nitrogen dissolves in the blood ► nitrogen narcosis results. The greater the depth, the more nitrogen dissolves.  Nitrogen interferes with nerve impulses, causes dizziness, and slow reactions.

Decompression Sickness  When a diver surfaces rapidly, the nitrogen leaves the blood suddenly; little bubbles form all over the body, blocking arteries and blood flow, causing nausea, pain, vomiting.  Divers coming from high depth have to sit in a decompression chamber that gradually lowers the air pressure.

Use of dive tables  calculating decompression stops and gas mixture, less N 2 in air when diving high depth

Practice  How many grams of Oxygen are contained in a 40 liter tank under 1000 kPa at -10 o C?  Hint: solve for n then convert into g – use PT