CHEM 1020 final reivew all units

How to calculate equilibrium constants using Kf and Kr

Concentration of products / Concentration of reactants

• Dont forget about the coefficient

K_f / K_r

Equilibrium equation (K_c)

K_c

When to use K_P and how to calculate it

reactions involving gases and is based on the partial pressures

• Same equation as K_c if using partial pressures instead of concentratiosn

• Uses diffrent equation if given concentration

What is homogeneous equilibria

Involve reactants and products in the same phase

Heterogeneous equilibria

Involve reactants and products in more than one place

Pure solid and pure liquids in equibrium

Its concentration is not included in the constant expression for the reaction

If K_c > 10³ products predominate over reactants at equilibrium, meaning

the reaction favors the formation of products.

Shifts in the forward direction

If K_c < 10-³ reactants predominate over products at equilibrium, meaning

the reaction favors the formation of reactants. Shifts in the reverse direction.

What does Q indicate

predicts direction of reactant

• Equation uses concentrations at non-equilibrium conditions

If Q is less than K

Shifts in the foward direction

If Q is greater than K

Shifts in the reverse direction

If Q is equal to K

The system is at equilibrium

3 factors of Le châtelier’s principle

1. Concentation

2. Pressure/volume

3. Temperature

If reactant or product is added than the reaction will shift in

the opposite direction the substance is added in

If reactant is added than it will shift towards the products

If a reactant or product is removed than the reaction will shift in

The direction the substance is removed in

If reactant is removed, it will shift towards the reactants

If volume decreases

If pressure increases

The reaction will favor the side of the reaction with the smaller number of molecules

If volume increases

If pressure decreases

The reaction will favor the side with the large number of molecules

When will volume and pressure have no effect

If the reaction has no change in the number of molecules

In an exothermic reaction heat should be treated as a

product

In a exothermic reaction if the temperature of a system increases

The equation will shift to the left (reverse direction)

In an exothermic reaction if the temperature of a system decreases than the equation will

will shift to the right (forward direction)

What do you treat heat as in an endothermic reaction

as a reactant

What happens if temperature increases in an endothermic reaction

Shifts to the right

What happens if temperature decreases in an endothermic reaction

Shift to the left

What is G^o at equilibrium

0

What does a large negative ΔG^o mean in relation to K

Large K

mostly products

What does a small negative ΔG^o mean in relation to K

Small K,

Mix of products and reactantss at equilibrium

What does a postitive ΔG^o mean in relation to K

Small K

The nuclear reaction that takes place in our sun is

fusion

The nuclear reaction which can be used to produce heat for the generation of electricity is

fission

How to find the K_c for the reserve reaction if given the forward K_c

it is the reciprocal of the equilibrium constant for the forward direction

How to calculate ΔG^o based of the G^o_f for reactants and products

G^o_f PRODUCTS - G^o_f REACTANTS

Q and ΔG

Largest Q has the largest ΔG

the rate of a reaction with a lower activation energy is ——- than that of a reaction with a higher activation energy because ———

Greater

number of successful effective collisions is higher

What three things is collision theory dependent on

1. Concentration

2. Temperature

3. Orientation

The rate of reaction is primarily related to what

the number of collisions, which is related to concentration

• The greater the frequency of collisions the more opportunity for reaction

What is Activation energy

The potential energy barrier that must be surmounted before reactants can be converted to products

2 qualifications for molecules to colldie with eachother

1. sufficient energy

2. proper orientation

As actiivation energy decreases what happens to K (rate constant)

Increases (indirect relationship)

As temperature increases what happens to K (rate constant)

Increases (direct realtionship)

How much will the temperature increase by if the reaction rate is doubled

10 degrees Celsius

If the products have a higher final energy than the reactants then the reaction is ,

endothermic

Overall reaction vs elementray steps

Overall: A → D

Elementrey:

• A → B

• B → C

• C → D

What is a reaction intermediate

a substance formed in one elementary step of the mechanism and consumed in another elementary step

Molecularity

The number of molecules (or atoms) on the reactant side of the chemical equation

Unimolecular elementary reactuion

• First order

• Has a single reactant molecle

Bimolecular elementary reaction

• Second order

• Has two reactant molecules

Know how to form an overall reaction from elementary steps

1. Cross out any intermediate products

2. Find the final reactants and products

3. Put them together

Termolecular

• Third order

• Not as common

• three reactant molecules

How to determine rate law for overall reaction

Must be determind expiermentally

How to determine rate law for elementary steps

From its molecularity

The experimentally observeved rate law for an overall reaction is dependent on waht

the reaction mechanism, which is the sequence of elementary steps

What is the RDS

Rate determining step

It is the slowest elementary step in a multistep reaction

The rate of the overall reaction is determined by the rate of this step

IMPORTANT NOTE about writing rate law for the overall reaction

an intermediate cannot be part of the reaction rate

What is a catalyst

a substance that increases the rate of a reaction by lowering the activation energy

How to identify a catalyst in a reaction

• Not consumed in reaction

• Not in final products

Homogeneous catalyst

• The catalyst exists in the same phase as the reactants

Heterogenous catalyst

• The catalyst and reactants are in diffrent phases

Know how how calculate rate by looking at pictures

which reaction requires the most energetic collisions to reach the transition state

The one with the highest activation energy

rate constant in comparison to activation energy

lowest AE has the highest rate constant

Highest AE has the lowest rate constant

activation energy and rate limiting

The reaction with the highest activation energy is considered to be rate limiting

What number is at the top of an isotope (A)

The mass number

Protons + neutrons

What number is at the bottom of an isotope

Atomic number

Alpha particles

⁴₂H

Beta particles

Released in the products

⁰_-1 e

One proton gets added to the element (changing the element)

Gamma radiation

Accompanies in alpha and beta emission

₀⁰Y

Positrons

⁰₁e

occurs when a proton is converted into a neutron and a positron

Electron capture

In the reactants

_-1⁰e

Ionizing power

the ability of radiation to ionize molecules and atoms

penetrating power

the ability of radiation to penetrate matter

alpha particls ionizing and penetrating power

Highest ionizing power

Lowest pentrating power

Beta partcles ionzing and penetrtating power

Middle of both

gamma rays ionzing and penetrating power

Lowest ionizing power

Highest penetrating power

Important half life equation to remeber

In( N_t / N₀) = -kt

What is an important measure for determining the stability fo the nucleus

Neutrons to protons ratio

(N/Z)

What happens if the N/Z ratio is too high

Neutrons are converted to protons via beta decay

What happens if the N/Z ratio is too low

Protons are converted to neutrons via positron emission or electron capture

• or via alpha decay though not as efficiently

Possible trick for N/Z ratios

If isotope mass is lower than it is positron emission

If isotope mass is higher than it is beta emission

What is nuclear fission

the fragmentation of heavy nuclei to form lighter, more stable ones

What is nuclear fusion

The formation of heavier nuclei by the joining of lighter ones

What is nuclear transmutation

The change of one element into another

What equation should you use to calculate energy changes during nuclear reactions

E = mc²

How to find m in E = mc²

m = m_reactants - m_products

Bronsted Lowry Acid/Base

Acid: Proton donor

Base: Proton acceptor

Lewis Acid/Base

base: donate pairs of electrons

Acids: accept pairs of electrons

what does HA stand for

HA is undissociated acid

% ionization and Ka relation

Higher Ka value acids lead to higher % ionization

concentrations and percent ionization relation

Lower concentrations have higher % ionizations

Acids and the periodic table groups

Acid strength increases down a specific group

If the pH @ equivalence is higher than 7

weak acid + strong base

Which way do electrons flow

Electrons flow from anode to cathode

If an element is doing the reducing it is being —-

oxidized

How to get rid of log

10^ans

How to get rid of ln

e^ans

Dead battery Ecell and Q

Ecell = 0

Q = K

Voltanic Cell, Ecell, G and K

Ecell > 0

G < 0

K > 0

Standard reduction potentials and oxidizing/reducing agents

More positive = Strong oxidizing agent

More negative = Strong reducing agent

Formula for Pka

Pka = -log(ka)

Strong base + Strong acid @ equivalence point

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