Chemistery S,R: 1,2

Atom

Basic ("smallest") unit of matter

1. Nucleus (composed of nucleons)

2. Elecrons on electron shells surrounding nucleus

Compound

1.Atoms of different elements chamically bonded in a fixed ratio
2.Characteristics differ from those of elements

3. Can be seperated through chemical reactions

Mixture

1. Contain more than one element/ compound in a non consistent ratio
2. Compounds retains its characterisics
3. Can be seperated using physical methods (e.g. filtration)
4. Compounds aren't chemically bonded

Element

Pure form of matter

1. made up of 1 type of atom
   2.Cannot be seperated into simpler substances
2. repsesented by chemical symobls
3. Characterisitcs defined by characteristics of atoms

Pure substances

One type of particle (element or compund)

Homogeneous mixture

uniform composition (e.g. salt water, pure juice)

Heterogeneous mixture

A mixture in which different materials can be distinguished (non unifom composition) (e.g. sand, milk products)

Colloid

Heterogenous mixtures that appear homogenous (e.g.milk)

Solvation

Chemical process where solvent molecules surround and interact with solute particles (ions or molecules) to form a solution

1. Solute particles must be attacted to polar water molecurles
2. They are surrounded by soluvent molesules forming a shell
3. "Like dissolves Like"

Filtration

1. Pure substance is dissolved
   2.Solution is fitered usign filtarion paper
   3.Seperation based on difference in particle size and soluability

paper chromatography

1. Method of separating a mixture of different colors. The liquid soaks through the paper and carries the mixture with it. Some substances are carried faster than others, so the substances are separated along the paper
2. Higher solubility (less intermolecular forces) between the stationary and the mobile phase allow particles to travel farther

recrystallization

1. A mixture is dissolved using hot water
2. As the mixtures cools non soluable particles
3. Seperation based on difference insoluablibity (pure substance needs to be soluable at high but not at low T)

Evaporation

1.A mixture is heated in evaporaiton until the substance with the lower b.p. evaporates leaving behind the second substance
2.Seperation based on b.p.

distillation

1. The mixture is heated in distillation falsk until substance with lower b.p. evaporates and enters the condenser where the gas in cooled down and undergos condensation.
   2.Seperation based on b.p.

Kinetic moelcular theory

Particpes of different state have diffelernt physical properties because they have different avergae kinetic energy

Solid (s)

1. Definite shape and a definite volume
2. Low kinetic energy and High attactive intermolecular forces compared to Ek
3. Particles vibrate but move very litle

Liquid (l)

1. no definite shape shape of container) but has a definite volume
2. Intermediate kinetic energy and IMFs
3. Particles move freely past each other

Gas (g)

1. No definite shape or volume
   2.High kinetic energy and low IMF's
2. Particles more freely

Aqueous (aq)

dissolved in water

Melting

solid to liquid

Freezing

liquid to solid

vaporization

solid to gas

1. Evaporation (change in state on top layer)
   2.Boiling (change of state throughout)

condensation

Gas to liquid

sublimation

solid to gas

deposition

gas to solid

Temperature (K or C)

Measure of Average kinetic enegry

T vs. t during change in state

T stays constant as the energy goes towards breaking/ forming bonds between particles

Gradient of T vs. t

Steeper gradient = larger change in T = higher specific heat capacity

Nuclear symbol

A= nucleon number
Z= Proton number
X =chemical symbol of element

Relative masses and charges of subatomic particles

Proton: 1, +1
Neutron: 1, 0
Elecron: Negligible, -1

What determines the differenct chemical properties of atoms?

Arrangement and number of electrons

How dose amotic number relate to the position if an elemt in the periodic table?

Elements are ordered by increasing atomic number

Isotopes

Atoms of same element with different numbers of neurtons

Physical properties of heavier isotopes: larger mass, density, b.p and m.p.

Relative atomic mass

((M1 x Abundance1) + (M2 x Abundance2)….+(MN x AbundanceN))/100

Mass spectra for isotopes

Used to determine the relative atomic masses of elements from their isotopic composition. (Diatomic elements have two "areas" on mass spetrum

How dose the fragmentation pattern of a compound in the mass spectometer help in the determiantion of its structure?

Gas discharge tube and prism

Creation of emission spectra: Made using gas discharge tube which sends beam of gas to deffract on a prism

Qual: emission specturm, distinct lines, element identification
Quant: wavelength, engergy and frequancy, line intensity

Emission spectra

A spectrum of the electromagnetic radiation emitted by a source, with each wavelength represeinting the energy emitted through a photon when electrons retun to lower energy levels

Color in specturm

1. Energy = (h x speed of light)/ wavelength
2. Longer wavelength = more red

Continuous specturm

Contains all wavelengths of light, merging seamlessly from one color to the next.
Produced by objects that emitt all wavelengths equally such as (e.g. hot molten metals or lightbulbs)

Line specturm

Specturm with thin lines of certain specific colors (mostly same for emission and absorbtion specturm) emitted e.g. by gas

Quantized engery levels

Only specifif values for the wavelength and energy of photons emitted (emission specturm) shows that electrons must jump between levels of discrete energys.

Energy level

Energy levels n = 1,2..n correspond to electron shells of ruthorford model
Number of electrons per energy level = 2n^2
Value n of highest enegry level = period

Sublevels

Each energy level is spilt into sublevels (s, p,d,f) which are succesivly higher in energy

Orbitals

Regions around the nucleus in which given electron or electron pair is likely to be found
S sublevel: ONE orbital that is is sphereical in shape
P sublevel: THREE orbitals(x,y,z) in shape of two elongated spheres

(Full) Electeon configuration

Aufbau princible: Electrons occupy lowest postible energy levels
Pauli exclusion principle: Orbital can hold two electrons with opposute spins
Hunds rule: Single electrons with the same spin must occupy each equal-energy orbital before additianal electrons can occupy the same orbital

Condensed electron configuration

Prior nobel gas in brackets and the remaining orbitals

orbital diagram

Electron confugration of Cr and Cu

Irregularities: Due to the stability of half-filled (nd5) or fully-filled (nd10) subshells, elements like Chromium and Copper skip fully filling the 4s2 shell, moving one electron to the d sublevel.

Trend in first ionization energy

Decrease down a group, increase to right in period because

1. Nuclear charge gets larger so attrection to nucelous get stronger
2. Distance to nuclus gets larger with energy levels and effect of electron shieling gets stronger

Discontinuities in first ionization energy IE

Between Groups 2 and 3:

• Electrons in group 3 have 1 electron on p-sublevel which is higher in energy and shielded by electrons in s-sublevel making it easier to revome

Between group 15 and 16
-Group 15 Electorns have a half-filled 2p sublevel, which is particularly stable and Group 16 electrons have electron-electron repulstion in s-sublevel, together making it easier to ionize group 15

Transition metals Cr and Cu

Limit of convergence

This occures when at high frequencys the lines in a line specturm become to close (converge) that their difference in wavelength/ frequncys eqals zero.

IE is the energy required when the wavelength absorbed is at the limit of convergence

Ionization energy

Energry required to remove 1 mol of electrons for gaseous atoms

How dose the trend in IE explain the trend in properties of mentals and non metals?

Metals have low IE = easily lose electrons (cations)
Non-metals have high IE = more resistant to lose electrons (anions)

Sucessive ionizaiton energys

1. Sucessive ionization energys increase (significantly) and commonly logs are used to plot successive IE

Deducing elements from sucessive IE

Very large jumpes indicate change in sublevel or energy level
e.g.
IE1: 500
IE2: 2300
IE3:10500
Jump from IE3 to IE2 --> two "low" IE so group 2

Variable oxidation state

transition (d-block) metals can have multible oxidation states becausue io
Greatest number for the oxidation state is in the middle of the d-block row

variable oxidation state

Having multiple oxidation states: The 3d and 4s sub-levels are very close in energy, so electrons from both sublevels can be lost.

Hydrogen emission specturm

Characteristics:

1. Produces a line specturm (evidence energy of electrons being quantized) with converging lines at higher wavelength (closer energylevels)
   To first energy level: UV region
   To second energy level: Visible light region
   To third energy level: IR region

Emission spectra as evidence for elements

Each elements has a unieq structure and energy levels, thus creating distinct emission spectra.

mole

SI unit for amout of substance
One mole = Avogadros constant number of particles

Relative atomic mass Ar

Mass of typical atom calculated in consideration of isotopes. Ar is a atoms mass realtive to C-12 as mass of 1 nucleon is 1/12 of a C-12 atom --> thus it is also unitless (ratio)
--> Value is equal to molar mass but definition differs

Mass of a atom

For heavier:

1. Density increases (mass inceases faster than radius), 2. Radius increases --> reactivity, b.p. and electronegativity

Empirical formula

Simplest ratio of atoms in a molecule e.g.(CxNy)n

• Found using precentage composition of masses

Molecular formula

Acctual number of atoms of an element present in molecule e.g. CxNy

Molar concentarion

[C]= n/V (square brackets required)
Unit: g/dm or mol/dm^3

Procusing a standart solution vs serial solution

Standart solution= Solution with an accurately known, precise concentration

• prepared using a volumetric flask
  Serial solution= Series of solutions with decreasing concentration by same factor (e.g. logarithmic)
• Usually made in test tubes: E.g. fill a line of test tubes with 9ml water then add 1ml of stock to first tube. Mix and add 1ml from first tube to second tube…

FInd concentation through calibration curve

1. Plot known standard concentrations (x-axis) of serial solutions against their measured responses (e.g., absorbance on the 𝑦-axis).
2. Calibrate unknown sample and find its peak wavelength (absorbance)
3. Absorbance is proportional to Concentraion, thus graph made in 1 can be used to find C for know value of A.

Avogadros law's

Equal volumes of all gases under same T and P have the same n/N.

Ideal gas

1. neglidigble volume of particles
2. no intermolecular forces
3. estallic collisions

Conditions for ideal gases

High T and Low P

• Gases with strong intermolecular forces and larger M or R deviate more

Molar volume

Volume occupied by 1 mol of gas at STP

Gas laws

PV/T is constant

Calcualting molar mass from experimental data and ideal gas equation

PV=nRT -->M=mRT/PV so if mass of gass is know we can find M

Avogadros law

Equal volumes of all gases at the sampe T and P contain the same number of molecules.

Explentation behvind avogadros law

Avogadros law is predicitve rather than explenatry and fails under non-ideal conditions (larger particles, low T or high P).

Explenation: Adding molecules increases collisions and thus pressure which, pushing the walls outward and increases the containers volume.

Limiting reactant

Reactend with smaller number of moles in considertation of molar ratios.

Theoretical yield

The maximum amount of product that can be produced from a given amount of reactant

Experimental yield

The amount of product profuced

Percentage yield

Experimental yield/theoretical yieldx 100

Atom economy

A measure of the efficiency of a chemical reaction by finding perccentage of amount of starting materials that end up form the useful products (e.g. if reaction onyl has 1 desired prodouct the atom economy is 100%)

Relationship between atom economy/ yield and waste in industry

Inverse: higher atom economy = less waste.
NOTE: This is quite simplified and accutally facorts like energy requirements, cost, or toxisisty or chemicals also affect if a certain reaction is effiecient and thus used.

Reaction rate

Change in concentration over time.
Note: can also me measured through change in mass, pH or volume

instantaneous rate

Tangent to a graph

Average rate

The change in concentration of reactants (or products) divided by total time period.

Mearusing reaction rate

Spectrophotometer: colorfull (e.g. Iodine, iron, Cu) --> concentration vs. time
Gas pressure sensor: Volume of gas producted over time
Mass change = percipitate produced e.g. marbel (CaCO3) measuring time untial cross is covered

Requirements of reactions

1. Particles must collide
   2.Colision with sufficient engery
2. Collise geometry: particles must collide with appopriate orientation (reactive parts come in contact)

Activation energy

Minimum energy required for reaction to occure

Temerpatures effect on the rate of reaction

Increases average kinetic energy of particles which in increasees their speed and freuency of collision and increases the amount of particles which posses nessesary activation energy (Maxwell-Boltzmann curve)

Maxwell-Boltzmann curve

number of reatinf particles vs. kinetic energy
area under curve= number of particles with a certain kinetic energy

Surfece areas effect on rate of reaction

For solids only surface area comes in contact with surrounding reactants. Thus larger surfance area e.g. powdered sig, increases reaction rate.

Concentrations effect if rate of reaction

More particles and more frequent collisions
Note: some exotermic reactions heat up environment siultaneously as concentration decreses compensating or increasing rate of reaction

Catalyst

Substance that speeds up the rate of reaction by offering an alternative reaction pathway lower in acivation energy, which is not consumed or changed in reaction

systematic error

measurment allways differs by the same amout form accutal value

random error

measuremt differs in unconsistent amouts from accutal value

persision

how close measurments are to each other

accuracy

how close a measurement is to the true value

How can graphs provide evidence of systenatic and random errors?

Systematic: non zero/ intial amout intercept, shifted, slope differs from theoretical value
Random: scattering, error bars

Energy profil

Axis: Energy vs. time
Difference between lines: Enthaply change

Enzymes

Biologial catalysts for chemical reactions in living things consisting of proteins