Chapter 11. Recall: States of Matter. Properties of Gases. Gases

Transcription

1 Chapter 11 Gases Recall: States of Matter Solids and Liquids: are closely related because in each case the particles are interacting with each other Gases: Properties of Gases Gases can be compressed Gases expand to fill their container uniformly All gases have low density Gases can be mixed A confined gas exert a constant, uniformed pressure on the wall of the container 1

2 The Kinetic Molecular Theory A gas consists of particles moving at any given instant in a straight line Particles collide with each other and the walls of the container without loss of kinetic energy Gas particles are very widely spaced The actual volume of the particles are negligible compared with the space they occupy Gas particles behave independent of each other Notes on Gases Gases have weight and exert a pressure n everything Gases undergo reactions Pressure Pressure is a force exerted by gas molecules as they collide with the surfaces around them. 2

3 Pressure Pressure Pressure Units The Gas Laws Used to look at the behavior of gases under different conditions Standard units Pressure: (P) atm Volume: (V) Liter Temperature: (T) Kelvin Amount of Substance: (n) Mole Gas Laws Boyle s Law Looked at volume and pressure P 1 V 1 = P 2 V 2 Held temperature and number of moles constant 3

4 Boyle s Law P 1 V 1 = P 2 V 2 Computation of the volume of a gas after a pressure change Boyle s Law P 1 V 1 = P 2 V 2 Computation of the pressure of a gas after a volume change Pressure and Volume Boyle s Law Boyle s Law The volume of a gas and its pressure are inversely proportional 4

5 Gas Laws Charles's Laws Looked at volume and temperature V 1 /T 1 = V 2 /T 2 Held pressure and number of moles constant Charles Law Volume and Temperature (Kelvin) Charles Law The volume of a gas and its temperature in Kelvin are directly proportional Charles Law Temperature in Kelvin Celsius Charles Law The volume of a gas and its temperature in Kelvin are directly proportional 5

6 Charles Law Computation of the Volume of a gas when the Temperature is changed Charles Law Computation of the Temperature of a gas when the Volume is changed Gas Laws Combined Looked at volume, pressure and temperature P 1 V 1 /T 1 = P 2 V 2 /T 2 Held number of moles constant 6

7 The Combined Gas Law Combines Boyle s Law and Charles Law Calculates Volume with a Temperature and Pressure Change Temperature with a Volume and Pressure Change Pressure with a Volume and Temperature Change Gas Laws Avogadro s Law Looked at the number of moles and volume Held pressure and temperature constant Increase number of moles means increase volume Direct relationship Avogadro s Law Volume and Moles Avogadro s Law The volume of a gas and the amount of the gas in moles are directly proportional 7

8 What is STP? STP is standard pressure and temperature T = 0.00 o C P =1.00 atm Use these values anytime a problem calls for STP conditions Ideal Gas Law What is an ideal gas? The ideal gas law: PV=nRT Can be used to calculate the temperature, number of moles, pressure or volume of a gas R is a constant = L atm / mol K All units must be the units found in R Ideal Gas Law Combines Boyle s Law Charles Law Avogadro s Law PV = nrt Pressure in atm Volume in liters Moles Temperature in Kelvin 8

9 Ideal Gas Law Ideal Gas Ideal Conditions Density For gases density is measure in g/l The density of an ideal gas is: d = m/v = [(MM)(P)] / [R T] Where MM is the molar mass of the gas or the average molar mass of a mixture of gases This equation come from the ideal gas law Mixtures of Gases Partial Pressure Pressure due to a single gas Dalton s Law of Partial Pressures Sum of the pressure of each component in a gas mixture equal the total pressure of the mixture 9

10 Gases in Chemical Reactions Stoichiometry Moles A Moles B Moles PV = nrt Balanced Chemical Reaction Coefficients give mole relationship Gases in Chemical Reactions Molar Volume at Standard Temperature and Pressure (STP) One mole of any gas at STP occupies 22.4 liters 10