Chemistry 12 - Unit 1 AND 2 Notes!! (25 and up is dynamic equilibrium!!)

Dynamic Equilibrium - Kinetic Distribution Graphs

Name all the 5 factors affecting reaction rates

• Temperature

• [ ]

• Pressure Increase

• Nature of Reactants

• Ability of reactants to meet (SA)

Define a homo and Hetero chemical reaction

Homo: Reactants are in the same phase

Hetero: Reactants are in different phases

Name each from fastest to slowest (Solid—-Aqueous—Gas/Liquid)

Aqueous (FASTEST) Gas/Liquid (FAST) Solid (SLOW)

What is an inhibitor?

Chemical that reduces rxn rate

REMEMBER: Rate at which reactants are getting used up equals the rate at which oriducts are gettug used up

Are homo or hetero reactions faster? why?

Homo because they are more adequately mixed

When a rxn is more stable, there is a (lower/higher) PE

Lower!

Def of activated complex

state where reactants re-arrange to form the product

Definition of activation energy

Minimum potential energy needed to reach activated complex

KE < Ea —→

No rxn

KE = Ea —>

Activated complex

KE> Ea—>

Will react

Enthalpy

Used to keep track of change in energy

IF KE IS TOO LOW RXN WILL NOT HAPPEN

How does a fast reaction appear on a distribution curve?

The activation energy line is further to the left, so a larger fraction of molecules have enough energy to react

How does a slow reaction appear on a KE distribution curve?

The activation energy line is further to the right, so a smaller fraction of molecules have enough energy to react.

number of molecules / KE curve desctiprion

Letter n and ME line

PE / rxn time curve desctiption

exo and endo line thingy

on a KE curve, what happens to the curve when you increase the temperature?

Lower hight. wider flatter shifts right on x axis

on a KE curve, what happens to the curve when you Decrease the temperature?

Higher Peak Hight. shifts left. shifts left on x-axis.

In slow rxns, a __°C temp increase doubles the rate

10!

2 Main Factors for reactions to occur

• Enough KE

• Correct Allignment

What do catalysts do physically to the graph?

Reduce activation energy

What is a rxn Intermediate?

A reaction intermediate is a substance that is formed in one step of a reaction and used up in a later step.

Definition of spontanious rxn

It occurs by itself

Are endo or exo reactions mostly spontanious?

Exothermic. (think of it like energy is leaving it. so that means you dont acc need to put anything in physically)

Why arent Endo rxns generally not spontanous

They need more energy to occur. require constant input of energy

why do endo rxns need more energy to occur?

because it absorbs more energy than it releases.

What two factors determine whether a reaction will be spontaneous?

Enthalpy and Entropy

What sides do enthalpy and entropy favor?

Enthalpy - Favors side with minimum energy

Entropy - favours Amount of randomness in a system

What are the conditions necessary for equilibruim?

1. Closed system

2. Reversable Reaction

3. Constant Temperature (again why exo is only spontaneous lol)

Charachteristics of Equilibruim

1. Fwd Rate = Reverse Rate

2. Constant Macroscopic Properties

3. Constant Reaction and Product Concentration Ratio

*system tries to undo that stress

What is Le Chatelier’s Principal?

When a system at equilibrium experiences a stress (change in concentration, pressure, volume, or temperature), it shifts to counteract that stress.

What is a stress?

It's an external change applied to a system at equilibrium, causing it to no longer be at equilibrium. They are immediate!!!!

On an equilibrium graph, what does the - - - - - - - - dotted line mean?

Thats when equilibrium is disrupted

What is different about concentration graphs?

No fwd/rev rate shown

What’s the effect on equilibrium when you add a catalyst?

No effect. (doesnt move left or right)

What 2 substances are NOT included in the equilibrium Keq expression? and why?

Solids: Their density cannot be changed. Therefore their molar concentrations cannot be changed.

Pure Liquids: Have a constant density and molar concentration

Why can't liquids be appreciably compressed?

Their volume changes very little under pressure.

What happens when another liquid dilutes a liquid?

Its concentration changes, so it is no longer pure.

When is a liquid considered pure in an equilibrium equation?

When it is the only liquid present on both sides of the equation.

ADDING OR REMOVING A PURE SOLID OR PURE LIQUID CAUSES NO SHIFT IN EQUILIBRIUM. WHY?

Their Concentration never changes no matter how much you dump in

if the Keq >>1 _______ are heavily favoured

Products

if the Keq<<<1 _______ are heavily favoured

Reactants

If Keq=1,

exactly in the middle!!

Automatically, when the products decrease, and the reactants increase, Keq decreases. why?

The overall value of the fraction is guaranteed to shrink

Why in this equation that is uploaded and how would you know that the C-section is - X and minus X And plus 2X?

You know this because the initial concentrations are at an imbalance. The HI is at zero that means it would shift to the right to balance it out.

If equilibrium shifts RIGHT, which rate is greater?

Forward rate > Reverse rate

f equilibrium shifts LEFT, which rate is greater?

Reverse rate > Forward rate (more reactants).

What does the Keq tell you?

whether reactants or products arefavored once the system reaches equilibrium.