P-Chem Unit 3

Chemical Equilibruim

Spontaneous change towards lower Gibbs

Dynamic Equilibrium

THe reaction will eventually reach this where there is no net chage

Finite change

the extent of the reaction

Exergonic

if Delta G < 0, forwards reaction is spontaneous

Endergonic

If delta G> 0 reverse reaction is spontaneous

Q

Reaction quotient

Pb/Pa

Q=0 before rxn happens

Q= infinity almost to completion, dividing by a really small number, almost any amount of A is gone

Can vary

Q=

K equilibrium constant

K

is equilibrium constant ratio of products and reactants

This is described as fugacity or activity

Does not impact results just definition

Activity

Means effect of concentration

Signed stoichianetric coefficient

+ for products and - for reactants

Q

activity of products/ activity of reactants

Activity are replaced by

certain forms and includes the activity unit

3 Ways to change a reaction

Pressure due to changes in volume degree of dissociation

Temperature K changes

Change concentration

Van’t Hoff eqn

The dependence of equilibrium constant K as a function of temp can be expressed by the

This For vapor pressure equilibrium, Slope is delta H, Non calorimetric way to find the equilibrium constants are

Galvanic Cells

These take advantage of spontaneous process of electrons going from one electrode to the other. Not to be confused with the ones you have to supply energy to have them

Vertical line

Means half reaction

phase boundaries- one is solid and the other is an ion

Couple them

node junction potential (double line) set up for salt bridge

Reduction

happens at the cathode (on the right)

Oxidation

Happens at the anode, is the reverse of the reduction

Kinetic Theory of gases

The gas sample consists of molecules of mass in constant random motion

The size of molecules is negligible “point like”

The molecules interact only through brief elastic collisions

(in reference to a near by molecule, the diameters of these molecules are much smaller than the distance between them)

A partition within a container with an opening

gas particles are not pulled through because of difference in pressure. As the gas molecule does its random walk- from A-B of gas molecules it is not a straight line- the reality is gases will go in whatever direction the Collison takes them why it is called the random walk

Diffusion

Movement of one species through another open a perfume bottle will eventual diffuse through the room

Effusion

Escape from an opening

Deflating of a balloon filled with He will deflate much faster than if you were to use a graph because they are moving faster- rate of effusion is a comparison

Molecular collision

Assume hard sphere approximation

Occurs when the separation between 2 spheres is distance d

Collisional frequency

Number of collisions per time

The most common type is from the side very unlikely for them to be lined up opposing

 

These resulting collusions are really from the side and has momentum in two direction and will have to follow diagonal which is why we have radical 2

Collisional Frequency

number of collisions a single molecule has per unit time

If we have a molecule that is considered to be spheric there is a certain collusion volume that it will have and that is where these terms come from

Mean free path

the average distance a molecule travels between collisions

Mean free path equation can from

simple assumptions- gas molecule is a simple sphere, there is only a collusion if it is within the collisional volume, we can look at the collusions in terms of time, this is where collisional frequency comes from

These equation tells you the distance traveled between collisions

Kinetic model of gases is only valid

Grahams law of effusion

Gives you the factor of how much faster the smaller is compared to bigger or how much slower the bigger is compared to the slower

Maxwell distribution

At a certain temperature gas molecules do not want to travel at same speed because they have collisions some will be faster and some will be slower due to the collisions-

collusion cylinder

As the molecule moves describe this known as

 there is a collusion where the distance to outer edge is 2d - if something is outside that