Kategoriak: All - heat - thermodynamics - temperature

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Vraj Rao - Mr. Z. Syed - SCH4U Grade 12 Chemistry

Thermodynamics deals with the study of energy changes and rates of reactions. Different materials require varying amounts of heat transfer to change their temperature, with water being an exception due to its high heat capacity.

Vraj Rao - Mr. Z. Syed - SCH4U Grade 12 Chemistry

Vraj Rao - Mr. Z. Syed - SCH4U Grade 12 Chemistry

Unit 4: Chemical Systems and Equilibrium

Acids and Bases
Miscellaneous

Solubility (Qsp)

Precipitate

An insoluble product that forms from a reaction between 2 soluble ionic compounds

Molar Solubility

The amount (in moles) of solution in 1L of saturated solution

Titrations

#3. Use Kw to calculate the concentration and find pH

#2. Determine the excess moles and new concentration

#1. Calculate the moles of Acid/Base

Equivalence Point

The point in a Titration where the amount of Acid present exactly equals and reacts with amount of Base present

A-B Titration Curve

A graph of pH of an acid/base solution vs Amount of ADDED acid/base

Amphiprotic Substances

Can act as an acid or a base

A molecule/ion which can accept/donate a proton

Final Concentration Calculations

#3. Re-calculate the concentration of the acid/base using the excess moles and the combined volume

#2. Find the difference between the two values and determin which one has excess

#1. Determine the MOLES of both, acid and base

Percent Dissociation

Ratio of concentration comparing ionized acid/base at EQLBM to original concentration of acid/base

% Dissociated = ( {}dissociated / {}initial ) *100%

Kb = Base-Dissociation Constant for the Ionization of a Base

Ka < Kb = solution is Basic

Ka = Acid-Dissociation Constant for the Ionization of an Acid

Ka > Kb = solution is Acidic

Kw = (Ka)*(Kb)

Can be re-arranged to solve for missing K_ value

#4. Calculate the Percent Dissociation

#3. Create and solve teh EQLBM expression

#2. Setup the RICE table and add values

#1. Calculate the concentration using pH

Strong vs Weak

The conjugate base of a Strong Acid is a weak base

A base that has LIMITED dissociation in water

A base that COMPLETELY dissociates into ions in water

The conjugate acid of a Strong Base is a weak acid

Weak

An acid that has LIMITED dissociation in water

Strong

An acid that COMPLETELY dissociates into ions in water

NEW

Bronsted-Lowry Theory

Conjugate

Conjugate Base

The particle remaining after a proton LEAVES an ACID

Conjugate Acid

The particle formed after a proton JOINS a BASE

Acid-Base Pair

A pair of 2 substances related by the gain/loss of protons

A proton Acceptor

A proton DONOR

FIRST

Arrhenius Theory

Base

A substance that contains HYDROXIDE ION (OH-) in its chemical formula

pH level above 7

Acid

A substance that contains HYDROGEN in its chemical formula

Ionizes in water to form HYDRONIUM ION

pH level below 7

Equilibrium

RICE Table

E = EQLBM value = Initial Amount - Change Variable

Solved using Keq = {products} / {reactants}

C = Change = Use variables

I = Initial Amounts (in concentration)

R = Reaction

Changes in Substances

Removing products

Adding products

Removing reactants

Shift to reactants side

Rf < Rr

Adding reactants

Shift to products side

Rf > Rr

EQLBM Constant Expression

#3. Substitute the respective values and solve

#2. Write the EQLBM expression

#1. Calculate the molar concentrations

K = {products} / {reactants}

let the EQLBM sign be represented as {=}

K = {C}^c + {D}^d / {A}^a + {B}^b

E.G. aA + bB {=} cC + dD

AKA Law of Chemical EQLBM , AKA Law of Mass Action

Concentration

{C} = solute / solution

Different Systems

Heterogeneous

An EQLBM system in which the components are in DIFFERENT physical states (e.g. gas, aqueous, solid, liquid)

Homogeneous

An EQLBM system in which all the components are in the SAME physical state (e.g. gas, aqueous, solid, liquid)

States of Equilibrium

Dynamic

Chemical (an example of Dynamic)

The state where the reaction vessel contains a mixture of all the reactants and products

One in which there is motion, despite there being no Net Change

Static

One in which there is NO motion

Le Chatelier's Principle

When a system at EQLBM is stressed, the syste, works to restore EQLBM once again

Types of Stress

Changes to the Pressure

Only affects EQLBM systems with unequal moles of Gaseous reactants and products

Changes to the Temperature

When temperature is decreased, Exothermic reactions are favoured

Consider HEAT as a Product in Exothermic Reactions

A + B = AB + Heat

Shifts to Products side

Shifts to Reactants side

When temperature is increased, Endothermic reactions are favoured

Consider HEAT as a Reactant in Endothermic Reactions

A + B + Heat = AB

If heat is removed

Shift to Reactants side

If heat is added

Shift to Products side

Changes in Concentration

System shifts to get back to the same ratio of reactants and products

Means that Keq is constant

Keep in Mind

At a given temperature, the reactants and products with ALWYAS be in the SAME RATIO at EQLBM, no matter the starting point

The Reactants are ALWAYS on the LEFT, and the Products are ALWAYS on the RIGHT side of an equation

All substances present are being made and unmade at the same rate

EQLBM constant K

Magnitude

Since products are divided by reactants in the expression:

A smaller K value (<1)

RVS reaction is favoured

A larger K value (>1)

FWD reaction is favoured

Dependence

Depends on the EQLBM concentrations

Depends on Temperature

Doesn't depend on the initial concentrations

Doesn't depend on the Reaction Mechanism

Generally, an equilibrium is a state of balance

RVS reactions occur slowly during the start, then speed up as product concentrations increase

FWD reactions occur rapidly during the start, then slows down as reactant concentrations decrease

The reactant and product concentrations are CONSTANT, not equal

Occurs when opposing changes (FWD and RVS reactions) are occurring simultaneously at the same rate

Both reactions occur until the concentrations of reactants AND products undergo no further change

Represented by an "equal sign" which has an arrow pointing the opposite direction on each line

Theoretically, all reactions are reversible

Reactions written R-L are RVS reactions

Reactions wrtiten L-R are FWD reactions

Unit 5: Electrochemistry

Oxidation and Reduction
Oxidation Numbers

#3. The unknown Ox. Numbers can be assigned algebraically and be solved using variables

#2. The total Ox. Numbers of a molecule/ion is the value of the charge of the molecule/ion

For neutral compounds, the Ox. Number of all the atoms must add up to ZERO

#1. Assign common Ox. Numbers

Use the Periodic Table of Elements

#7. The sum of all the Ox. Numbers of all the elements in a polyatomic ion equals the charge on the ion

#6. The sum of the Ox. Numbers of all the elements in a compound is ZERO

#5. In covalent compounds that do not contain "H" or "O" the more EN element is assigned an Ox. Number that equals the negative charge it usually has in its ionic compounds

#4. The Ox. Number of Oxygen in its compounds is usually -2, but there are certain exceptions

#3. The Ox. Number of Hydrogen in its compounds is +1 except in metal hydrides, where the Ox. Number of Hydrogen is -1

#2. The Ox. Number of an element in a monotomic ion equals the charge of the ion

#1. A pure element has an Ox. Number of ZERO

An arbitrary system based on charge of ions and EN

Used to keep track of electrons during reactions

Half-Reactions

A balanced chemical equation that shows the number of electrons involved

To monitor the transfer of electrons, represent each reaction seperately

Agents: One reactant causing a change in the other reactant

Reducing Agent

Therefore, this reactant is OXIDIZED

The reactant which causes the other to be REDUCED

Oxidizing Agent

Therefore, this reactant is reduced

The reactant which causes the other to be OXIDIZED

Both reactions happen SIMULTANEOUSLY - referred to as REDOX reactions
Modern Definitions

LEO the lion says GER

Gain of Electrons - Reduction

Loss of Electrons - Oxidation

The atom/ion that GAINS electrons

The atom/ion that LOSES electrons

Historical Definitions

Reduction

From metallurgy - producing metals from their compounds

Oxidation

Reaction of substances with oxygen (combustion OR corrosion)

Net Ionic Equations

At the end, the equation can be confirmed by counting all the atoms and charges on each side and making sure they are balanced

#3. Complete the Net Ionic Equation

All the spectator ions (those which are the same on both sides of the equation) cancel out, and the final equation is written from the remaining components

#2. Turn the chemical equation into an Ionic equation

All the aqueous are separated into its component ions

#1. Chemical equation

Normal equation written in the chemical names

Solids, liquids, or gases do NOT dissociate (completely ionize) in water
Any aqueous compounds completely ionize in water

Unit 3: Energy Changes and Rates of Reaction

Reaction Rates
Reaction Mechanisms

Predicting Mechanisms

#3. All the elementary steps must add up to the overall equation

#2. The slowest step (Rate-Determining-Step) must be consistent with the rate equation

#1. Each step must be elementary

Involve no more than 3 reactant molecules

Only best guesses at the behaviour of molecules

The overall reaction can only be as fast as the slowest elementary process (AKA Rate-Determining-Step)

Occur over a set of stpes

Each step of the mechanism is known as "Elementary Process"

Rate Law Exponents

Exponents are related to the "Order of the Reaction"

Order of the Reaction

Overall order = m

Unit of K = L ^(m-1) / mol ^(m-1) *s

The sum of the rate law exponents

Experimentally determined by changing 1 reactant at a time and looking at how the reaction rate changes

Rate Equation

rate = K {A}^x {B}^y

Exponents of the Rate Law are NOT related to the coefficients, of the balanced chemical equation in any way

K = the rate constant, determined by the reaction and the conditions the experiment was conducted in

The x and y values are determined by the actual experiment

In the sense where A+B = C + D

Rate is measured in moles per litre per second (mol/L*s)

rate = delta concentration / delta time

Factors Affecting Reaction Rates

#5. Catalyst

It lowers the amount of required energy for the reaction to occur

Also known as Activation Energy

A compound that increases the rate of a chemical reaction without being consumed in the actual reaction

#4. Temperature

Increased temperature is due to increased particle motion

Greater the motion of a particle, the greater the chance it will encounter another reactant

Higher the temperature = Higher the reaction rate

#3. Concentration

More chemicals result in more particles which can participate in the reaction

Higher the concentration = Higher the reaction rate

#2. Surface Area

Increase in surface area = Increase in the reaction rate

Homogeneous Reaction

All the reactants are in the same phase/state

Heterogenous Reaction

The reactants are in different phases/states

#1. Chemical Nature

Alkali metals later founds (first found only in compounds)

Due to high reactivity

Precious metals are discovered first

Not very reactive

Rate of Reaction

Reactions that require a GREATER number of particles to collide at the same time will DECREASE the chances of a successful reaction to occur

Rate Theories

Catalysts

Transition State

Collisions

Chemical reactions indicate the overall changes that is observed

How quickly reactants disappear to form products

Thermodynamics
Hess's Law of Summation

#4. Add the equations and enthalpies together (cancel out any repeating chemicals)

#3. Multiply the equations by factors such that they match the desired equation (multiply the enthalpies by the same factor)

#2. Arrange the equations so that your desired reactants are on the LEFT side and the products are on the RIGHT side

#1. Number each given thermochemical equation

Rules

#3. When cancelling compounds for Hess's Law, the state of the compounds is really important

#2. When a reaction is reversed, the sign of "H" must also be reversed

#1. If all the coefficients of an equation are multiplied/ divided by a common factor, the "H" must be changed likewise

The "H" is the same as the sum of the values of the "H" for each individual step

Calculations

Enthalpy of Formation (delta Hf)

The (delta Hf) for elements in their standard states are ZERO

delta H = sum of (delta Hf of products) - sum of (delta Hf of reactants)

The amount of heat absorbed/released when 1 mole of the substance is formed at standard temperature (25 degrees Celsius) from its elements in their standard states

Molar Enthalpy

The change in enthalpy on a per-mole basis

Enthalpy

Total kinetic and potential energy of a system at a constant pressure

Heat Capacity

c = heat capacity (in Joules/Celsius) q = quantity of heat transferred (in Joules) delta T = temperature (in degrees Celsius)

c = q/T q= cT

The amount of heat transfer required to raise the temperature of a sample by 1 degree Celsius/Kelvin

Specific Heat Capacity (c)

c = specific heat capacity (in Joules/Grams*Celsius) q = quantity of heat transferred (in Joules) m = mass (in grams) delta T = temperature (in degrees Celsius)

c = q/mT q=mcT

The amount of heat transfer required to change the temperature of 1 gram of a substance by 1 degree Celsius/Kelvin

First Law of Thermodynamics

Energy cannot be created or destroyed

The total amount of energy in the universe is constant

Important Terms

Temperature

The measure of internal energy of an object due to particle motion (kinetic energy)

Heat

The transfer of energy due to contact

Definition & Importance

Calorimetry

A calorimeter is used to perform this task, while a Bomb Calorimeter is a high tech version of this

The measure of heat change due to a chemical reaction

Changes in a System

Exothermic Reaction

If the system releases energy and the surroundings gain energy

Endothermic Reaction

If the system absorbs energy and the surroundings lose energy

Different types of matter require different amount of Heat Transfer to change the same temperature

Water is unusual - it can absorb/release a lot of hear without the temperature drastically changing

All chemical reactions result in Heat Transfer

Understanding heat transfer properties is important for building sufficient materials

Unit 2: Organic Chemistry

Organic Reactions
Alcohols and Related Reactions

Ethers

#4. Join the "oxy" branch to the larger Hydrocarbon group

Listed in alphabetical order

#3. Consider the smaller hydrocarbon group to be a branch that contains "O"

Add "oxy" to the root

#2. Give the longest Alkyl group an appropriate hydrocarbon name

Include any branches / other functional groups as necessary

#1. Identify the longest Alkyl group as the Parent alkane

2 Alkyl groups (the same or different) attached to an "O" atom

Formed by Condensation reaction, when 2 alcohol molecules react

Amides and Amines

Organic compounds that contain "N"

Amide

#2. Replace the "-oic acid" ending of the Parent acid with "-amide"

#1. Locate the part of theAmine that contains the C=O group and name the Parent Carboxylic acid that this part derives from

Keep in mind, the C=O group is ALWAYS given the number 1 position

Amine

#3. Include the position number if required

#2. Replace the "-e" at the end of the Parent Alkane with "-amine"

#1. Identify the largest Alkyl group attached to the "N" atom as the parent Alkane

Esters

#2. Convert the "oic acid" ending of the carboxylic acid to "oate"

#1. Convert the suffix "(a)nol" ending of the alcohol to "yl"

Made by joining an Alcohol and a Carboxylic Acid - 2 parts, 1 comes from each

Ketones

#4. Any substituents are named as per usual rules

#3. Indicate the position of the Carbonyl using the L.P.N. coefficient

#2. Remove the "e" and add the "one" as the ending

Carbonyl group is attached to a C that is not at the end

Aldehydes

#4. Branches are named as per usual rules

#3. This carbonyl group is assigned as C-1

#2. Remove the "e" and add "al" as the ending

#1. Take the longest chain containing the Carbonyl group

Carbonyl group is attached to the end C

Phenol

When benzene contains 1 single hydroxyl group the common name is used as its UIPAC name

Alcohol

Classifications - according to the type of Carbon to which the "-OH" group is attached

Tertiary (3)

Secondary (2)

Primary (1)

#3. Alcohol suffix comes after the Hydrocarbon suffix, minus the "e"

E.G. Methene + -ol = Methanol

#2. Chain is numbered so as to give the alcohol unit the L.P.N.

#1. Root name based on longest C chain with -OH attached

Contains the hydroxyl group (-OH)

Can be prepared by adding Water to an Alkane

Elimination

Zaintsey's Rule

The poor get poorer

Common place amongst alcohols and alkyl halides

The reverse of an Addition reaction (double bond is usually formed)

Addition

Markovnikov's Rule

The rich get richer

Alkenes & Alkynes have a greater tendency to undergo this reaction

Hydrogen, Halogens, Hydrogen Halides, and Water can be added

Substitution

C-C bonds in Alkanes are difficult to break

Usually "H" replaced by a Halogen atom

An "H" atom(s) are substituted by a different atom(s)

Functional Groups
General "in-case" Rules

First Point of Difference

Alphabetical order

Diagrams

Line diagram

Vertex of each line is a carbon, Hydrogens not mentioned

Condensed diagram

Understood as carbons are beside carbons (short forms used)

Structural diagram

Similar to Lewis diagrams

Alkynes (-YNE)

#2. Location number

#1. Number of C in longest chain

Hydrocarbons with triple bonds

Alkenes (-ENE)

Trans-

Longest C chain forms Z shape

If the 2 alkyl groups, C, of the parent chain are on the OPPOSITE side of C=C

Cis-

Longest C chain forms U shape

If the 2 alkyl groups, C, of the parent chain are on the SAME side of C=C

Where there's more than 1 double bond, add "a" to the end of the prefix (e.g. meth=metha)

lowest numbers are Priority

#3. Suffix family

#2. Insert the number for where the double bond is located

#1. Root name = longest continuous C chain, with double bonds

Hydrocarbons with double bonds

Alkanes (-ANE)

Other "Add-ons"

Aromatic Hydrocarbons

Contain a benzene ring as a base

PARA

P-

META

M-

ORTHO

O-

Structural Isomers

Compounds with the same molecular formula but with different bonding arrangements

Haloalkanes

Alkanes with halogen atoms

Cycloalkane

Ring like structure of alkanes

#3. Identify which numbers of substituents are connected to the C chain

#2. Find all the substituents and name them correctly from the chart

#1. Find the longest C chain and number them appropriately in ascending order (find the correct name from the chart)

Hydrocarbons with single bonds

Naming Hydrocarbons
Basic Naming Rules

#3. Assign numbers (locants) to the principal functional group as lowest common chain

#2. Identify the root (longest continuous chain of Carbons)

#1. Identify the suffix

Components of Names:

Suffix: The functional group

Suffix Names:

Root: The number of Carbons in the largest chain

Root Names:

*insert pic*

Organic Molecules
Organic Compounds

Carbon allows diversity

It can makes 4 bonds: a combination of Single, Double, or Triple bonds

Contain only: - Carbon - Hydrogen - Oxygen - Nitrogen

56,204,570 organic substances have been recorded to date

Unit 1: Structures and Properties of Matter

Hybridization
sp = Linear sp^2 = Trig. Planar sp^3 = Tetrahedral sp^3d = Trig. Bypyram. sp^3d^2 = Octahedral ETC

Number of hybrid orbitals that form = Number of atomic orbitals that combined to make the hybrid orbitals

Triple Bond

Involves 1 SIGMA and 2 PI bonds

Double Bond

Involves 1 SIGMA bond and other PI bonds

Single Bond

Involves 1 SIGMA bond

Principals

#3. Concept of atomic orbital hybridization is used

#2. Should be MAX orbital overlap

#1. Region of orbital overlap has a MAX of 2 electrons

Molecular Orbital Theory

Covalent bond formation and molecular shapes based on the formation of new molecular orbitals

Valence Bond Theory

Covalent bond formation and molecular shapes based on orbital overlap

Forces
Strongest to Weakest

#5. Dispersion forces

#4. Dipole-Induced Dipole interactions

#3. Ion-Dipole interactions

#2. Dipole-Dipole interactions

#1. Hydrogen bonding

Intermolecular

4 Categories

Occurs because NP molecules spontaneously form temp. dipoles

Weak attraction between all molecules

Dipole-Induced Dipole

Attraction between an ion and a temp. dipole of a NP molecule

Attraction between a polar molecule and a temp. dipole of a NP molecule

Possible to induce formation of dipoles in NP molecules

Electrons in atoms are in constant motion

Ion-Dipole

Can occur between

Polar molecule (positive end) and anion

Polar molecule (negative end) and cation

Cations usually smaller than anions

Attraction between partial charges of polar molecules/ions

Dipole-Dipole

Contribute to higher melting/boiling points in polar molecules

Polar molecules are more attracted to each other than similar N-P molecules

Attraction between opposite partial charges of polar molecules

Forces exerted between molecules/polyatomic ions

Forces of attraction/repulsion between molecules

Influence physical properties of substances

Intramolecular

Forces excerted within a molecule/polyatomic ion

Molecular Shape and Polarity
Polarity

When bonding is polar

a bond dipole is created

The less EN atom has a partial positive charge

The more EN atom has a partial negative charge

When 2 atoms bond

Sharing of a pair of electrons can be polar, non-polar, or ionic

Bonds

Use electronegativity to predict the polarity of each bond

#4. Draw in teh bond dipoles

#3. Add electronegativity of the atoms and assign (lamda+) and (lamda-) to the bonds

#2. Draw VSEPR diagram based on Lewis structure

#1. Draw the Lewis structure

A molecule may have polar bonds but may not be polar

Types

Non-Polar Covalent

Polar Covalent

Ionic

Structures
VSEPR

Steps

#3. Use VSEPR Notation to determine the molecule's shape

AXmEn

A = Central atom X = Bonding set m = Number of bonding sets E = Lone pairs n = Number of lone pairs

#2. Identify the charge clouds as bonding electrons or as lone pairs

#1. Draw Lewis-Dot-Diagram for the molecule and count the number of electron charge clouds surrounding the atom

Lewis Dot Diagrams

Write the chemical name of the substance and draw its valence electrons around it in a circle. Keep in mind the sharing of electron pairs in compounds

Atoms
Bohr Model

Binding Energy

Rydberg's Constant (Rh) = 2,18^10^-18 J

E = Rh/n^2

Emission Spectrum = Absorption Spectrum

Energy released when an electron falls from level 4 to 1 is the same amount of energy required for an electron to jump from level 1 to 4

delta Ejump = delta Efall

Electrons orbit the nucleus at certain discrete distances

Energy of shells increase as one proceeds away from the nucleus. Electrons only gain/lose energy by jumping from an allowed orbit to another

Specific quantities of energy/light are required for an electron to "jump" to a higher orbit - AKA - specific elements absorb specific quantities for energy/light

Orbits have defined energies called shells/levels

Light
Emission Spectrum

1880s by J.J. Balmer

WL = B (n^2/n^2-m^2)

WL = wavelength of the light emitted B = Balmer constant for Hydrogen = 364.50682 m n = integer such that n>m m = 2

Specific WL given off by the light of atoms

Compton Effect

Loss of frequency from shattered X-ray suggests that X-rays have momentum, because light can have properties and behave like Matter

Photoelectric Effect

Einstein later explained

Light itself consists of individual quantum particles, called Photons

1887 by Heinrich Hertz

Certain metallic surfaces lose their negative charges when exposed to light/electricity (not the light's intensity)

Frequency of light determines how quickly the metal would lose its charge

Planck's Constant

Matter absorbed/emitted energy in whole number multiples of hv

Shows that energy can only be transferred in "packets" AKA quantum (plural is quanta)

Terminology

Dispersion

As WL increases, bending decreases

The amount of bending that occurs depends on WL of light

Refraction

Whenever light goes from 1 medum to another, at an angle, the angle changes, making the light beam beng

Wavelength and Frequency

Frequency: The number of cycles (WL) per second that passes a given point

Pattern of peaks and troughs

Trough: Botom of pattern

Peak: Top of pattern

Electromagnetic Spectrum

Shows the types of ER arranged in order of decreasing wavelength

Many types of ER in addition to visible light

Carries energy through space

A type of electromagnetic radiation (ER)

Subatomic Particles
Protons

Rutherford adjusted his experiment

Concluded that Hydrogen ions are fundamental particles - called them Protons

Bombarded "N" atoms, and noticed that Hydrogen ions were released

Electrons

1897 by J.J. Thomson

Concluded that the rays were in fact small negatively charged particles - called them Corpuscles (we now call them electrons)

Went on the propose the Plum Pudding Model

Observed how they rays were bent by magnets, and how it could help estimate the mass of the rays

While working with cathode rays

History of the Atom
Dalton

Atomic Theory

Different elements have different atoms

All atoms of a particular element are identical

Matter is composed of indivisible particles

Law of Multiple Proportions

The masses of one element that can combine chemically with a fixed mass of another element are in a ratio of small wholes

Proost

Law of Definite Proportions

Different samples of any pure compound contain the same elements in the same proportions by mass

Lavosier

Law of Conservation of Mass

Mass is neither created or destroyed, only conserved

Democretes

Thought experiment

After each cut, the identity would be unchanged

Eventually reach a piece that cannot be cut

Atomos

"What would happen if matter could be cut in half an infinite number of times?"

Empedocles

Proposed that Matter was made of 4 elements (fire, air, earth, water)