Chem Gases and Kinetics

Kinetic Molecular Theory

explains the behavior of an ideal gas in terms of motion or their particles

ideal gas

a theoretical gas thats under conditions of high temperature and low pressue; closely adheres to kinetic molecular theory

real gas

all gases that exist in real life; are not ideal

temperature

measure of the average kinetic energy

pressure

the force of pushing/squeezing measured in atmospheres (atm) or kPa

volume

the amount of space an object takes up

Boyle’s Law

At constant temp, as volume increases, pressure decreases, and vice versa

• V & P have reciprocal relationship

Charles’ Law

At constant pressure, as temp increases, so does volume, and vice versa

• T & V have parallel relationship

Gay-Lussac’s Law

at constant volume, as temperature increases, so does pressure, and vice versa

• T & P have parallel relationship

Combined Gas Law

shows the relationship between pressure, volume, and temperature of a gas

Avogadro’s Law

equal volumes of gases at the same temp and pressure contain the same number of molecules

Average Kinetic Energy

measure of how quickly particles are moving (measured as temperature)

vapor pressure

how bad a liquid wants to become a gas (related to boiling point and evaporation)

Normal Boiling Point

the temperature at which a substance boils at standard pressure

Phase equilibrium

state where 2 phases are in equillibrium

What are gases called that follow Kinetic Molecular theory?

Ideal

What are the 5 postulates?

1. gases contain particles that are in constant, random, straight-line motion

2. when gas particles collide, there is no loss of energy, rather a transfer (elastic collisions)

3. gas particles are very small and the space between them is very large, so volume of individual particles is negligible (V container is considered V gas)

4. gas particles don’t attract one another (no IMFs because they’re far apart)

5. the temperature is directly proportional to the temp of the sample in K or C

PLIGHT

Pressure low, ideal gas, high temperature

What gases follow PLIGHT?

ideal gases

Pressure

how hard the gases bounce off the walls of the container, force of pushing measured in atmospheres (atm), kilopascals (kPa), mmHg, or torr

in this unit, all calcuations go to which number of sig figs?

3 sig figs

What is the formula for Boyle’s Law?

(PV)1 = (PV)2

What is the formula for Charles’ Law?

(V/T)1 = (V/T)2

What is the formula for Gay-Lussac’s Law?

(P/T)1 = (P/T)2

What is the formula for the Combined Gas Law?

(PV/T)1 = (PV/T)2

What is the formula for the Ideal Gas Law?

PV = nRT

where n = number of moles R = gas constant T = temperature (K)

Standard pressure measurements

• 1 atm

• 101.3 kPA

• 760 mmHg

• 760 torr

All gas laws use the ___ temperature scale

Kelvin

How is Kelvin similar and different to celcius?

same scale, but Kelvin is shifted upwards to not include negative nu,bers

What is zero kelvin (OK) called?

absolute zero

absolute zero

where atomic motion stops

STP

standard temperature and pressure

Stoichiometry

the relationship between the quantities of reactants and products before, after, and during chemical reactions

What do coefficients represent in chemical equations?

moles or liters

At STP, 1 mole takes up how much space?

22.4L

Vapor pressure

the stength of liquid molecules pushing against the atmosphere

Relationship between temperature and vapor pressure

as temperature increases, vapor pressure increases because particles have more energy

High vapor pressure

• very eager to become gas

• low BP

• weak IMF

Low vapor pressure

• rather be a liquid; don’t want to evaporate

• high BP

• strong IMF

Boiling point

when atmospheric pressure = vapor pressure

Normal Boiling Point

at STP water boils at 100C or 373K

Collision theory

describes what is needed for a chemical reaction to take place; particles must collide with proper energy and orientation

Effective collision

the collision of molecules that have the right energy and orientation to form a chemical reaction

When temperature increases, molecules…

gain energy and move faster

What does it mean to increase concentration?

there’s more molecules in the system

What does increasing surface area in a chemial rxn do?

• allows more molecules to be a part of the reaction

• makes molecules unshielded by one another

What does increasing pressure in a chemial rxn do?

keeps gasses dissolved and able to react

What does introducing a catalyst in a chemial rxn do?

provides an alternate reaction pathway (shortcut) for the reaction

Wayts to ensure effective collision

• increase temperature

• increase concentration

• increase surface area

• increase pressure

• introduce a catalyst