CHEMISTRY FULL SET

contains modules 5,6,7 and 8

environmental monitoring

the processes and activities required to characterise and monitor the quality of the environment. Used in preparation of environmental impact assessments (where human activities pose a risk of harm to the natural environment)

environmental impact assessments

analytical chemists are often given the task of monitoring chemical components within the environment, such as:

• air quality monitoring

• soil monitoring

• water quality monitoring

air quality monitoring

air pollutants are both naturally occurring and anthropogenic (i.e. pollutants originating from human activity)

• may have negative impacts on abiotic and biotic components of the environment

• development of chemicals and industrial processes had led to the introduction or elevation of pollutants into the atmosphere

  • e.g. nitrogen oxides, ozone, sulphur oxides, CFCs

soil monitoring

_________ analysis, of its quality, constituents, and physical status to determine its use

• factors affecting it include: compaction, contamination, organic material loss, biodiversity loss, slope stability issues, erosion, salinization and acidification

• helps us characterise potential risks to soil, surrounding environments, animal health and human health

• e.g. salinity, presence/absence of essential nutrients used for agriculture

water quality

refers to the chemical, physical, and biological characteristics of water

• measured against set standards, measures condition of the water relative to the requirements of one or more species or to any human need or purpose

potable water

the safety of human contact and suitability of the water for drinking purposes

water pollution

the contamination of water bodies (e.g. lakes, rivers, oceans, aquifers and groundwater), resulting when contaminants (e.g. chemicals, pathogens) or physical changes (e.g. elevated temperature, discolouration) are introduced to the natural environment

• chemicals such as calcium, sodium, iron, nitrate, phosphate ions are naturally occurring → concentration determines whether these are contaminants

• high conc of these substances can have -ve impacts on flora and fauna

• e.g. oxygen-depleting plants like blue-green algae in an aquatic environment

• e.g. other natural substances that can increase turbidity, which blocks light and disrupts plant growth (limits photosynthesis) and clogs up gills of fish

eutrophication

an increase in the concentration of nutrients in an ecosystem which increases the number of producers in the ecosystem

depending on the degree to which this occurs, effects such as anoxia or oxygen depletion and severe reductions in water quality may occur subsequently (if the concentration is too high)

organic water pollutants

• detergents

• insecticides and herbicides: a range of organohalides and other compounds

• petroleum hydrocarbons, including fuels and lubricants and fuel combustion by-products, from storm-water runoff

• volatile organic compounds, such as industrial solvents, from improper storage

• various compounds found in personal hygiene and cosmetic products

• pharmaceutical drugs and their metabolites, which can include antidepressant drugs or hormonal medicines, such as contraceptive pills

inorganic water pollutants

• acidity caused by industrial discharges (e.g. SO₂ from power plants may lead to acid rain)

• chemical waste, as industrial by-products

• fertilisers: containing nutrients, nitrates and phosphates, which are found in runoff water from agriculture, as well as residential use → leads to eutrophication

• heavy metals: from motor vehicles, industrial discharges and acid mine drainage

• silt: from construction sites, logging, agricultural practices or land clearing sites (i.e. turbidity)

macroscopic pollutants (large visible items polluting water)

• garbage (e.g. paper, plastic, food waste) discarded or washed into storm drains

• nurdles and microplastics

• shipwrecks and large derelict ships

nurdles

type of pollutant; small ubiquitous waterbourne plastic pellets

thermal pollution

from water that was used as a coolant by power plants and manufacturing

heavy mining pollution

• Lead (from mining, leaded fuel and old paints)

• Mercury (from old batteries and mining)

• Cadmium (from burning fossil fuels

Are all found in sediments at the bottom of lakes from years of dumping leads to accumulation of these heavy metals which are released into the environment

bioaccumulation

gradual buildup of harmful chemicals and toxins inside a single living organism over time

flame test

a qualitative analytical technique used to detect the persence of metal ions.

When the cation is ‘excited’ by strong heating, electrons can be promoted from ground state to a higher energy level (orbital) → Law of Conservation of Energy, they have to lose the energy which is emitted as a photon of a certain wavelength based on the type of transition which have different wavelengths and are thus different colours for different elements

Barium ion (Ba²⁺)

(pale) apple green flame

calcium ion (Ca²⁺)

reddish brown (or orange-red) flame

magnesium ion (Mg²⁺)

colourless flame (bright white, blinding -- teacher has said not to look directly at it)

lead (II) ion (Pb²⁺)

blue-grey flame

silver ion (Ag⁺)

colourless flame

copper (II) ion (Cu²⁺)

blue-green flame (white flashes)

sodium ion (Na⁺)

orange-yellow flame

iron (II) ion (Fe²⁺)

gold flame (very hot), blue-green to orange-brown flame

iron (III) ion (Fe³⁺)

orange-brown flame

SNAAP Rule of Solubility

Salts that contain one or more of the following ions ARE soluble:

• Sodiun

• Nitrate

• Ammonium

• Acetate

• Potassium

NAG/SAG/PMS

NAG (always soluble):

• nitrates

• acetates

• group 1A metals

SAG (generally soluble, with exceptions):

• sulfates (SO₄^2-)

  • exceptions: Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Ag⁺

• ammonium

• group 7A halides (Cl^-, Br^-, I^-)

  • exceptions: Pb²⁺, Ag⁺ Hg²⁺

PMS (exceptions to SAG)

• P - (lead = Pb)

• M - (mercury = Hg)

• S - (silver = Ag)

coordination complexes

aka complex ions that carry a net charge (e.g. [Fe(SCN)]²⁺)

• are soluble in water

coordination compounds

aka. neutral complexes (same as coordination complexes but are neutral)

ligands

molecules/ions that come off of the central metal ion in a coordination compound

coordinate covalent bond

special type of covalent bond that ligands form with the central metal ion (ligands donate two electrons to form this bond different from regular covalent bonds where one electron is donated by each participant)

quantitative analysis

uses various chemical techniques and processes to determine the quantity of cations and anions in a certain amount of sample

gravimetric analysis

a procedure in which the masses of substances are measured to determine the composition of a sample (number of ions present can be determined using stoichiometry)

disadvantages:

• generally time consuming

• substance has to have specific properties for a precipitate to form (insoluble, be the only precipitate that forms, unable to decompose during the process, have a known chemical formula)

precipitation titrations

use precipitation reactions to determine the quantity of a chemical species in a sample

Mohr’s method

used to determine the concentration of anions such as chloride, bromide and cyanide by direct titration using a known concentration of silver nitrate.

Chromate ions are used as an indicator

NOTE: after the endpoint, the additional silver ions react with the chromate indicator, forming a red-brown precipitate of silver chromate

spectroscopy

the study of how matter interacts with electromagnetic radiation, revealing composition, structure and properties

spectrophotometry

a specific, quantitative technique within spectroscopy that measures the instensity of light absorbed or transmitted by a substance at different wavelengths to determine its concentration or quantity often using the Beer-Lambert Law

Beer-Lambert Law

states: “the concentration of a chemical is directly proportional to the absorbance of a solution”

A = εcL = log₁₀(I₀/I)

where:

A = absorbance

ε = molar absorption coefficient (M^-1cm^-1)

c = molar concentration (M)

L = optical path length

I₀ = incident intensity (original intensity - light entering the sample)

I = final intensity (light exiting the sample)

Colourimetry

A type of spectrophotometry in which colour is used to determine the concentration of a chemical species in a solution

UV - visible spectrophotometry

Uses the ultraviolet and visible regions of the EM spectrum to excite electrons — uses a calibration curve to determine the concentration of the molecule in a sample

Atomic Absorption Spectroscopy (AAS)

Uses the absorption of light by electrons (in their ground state) in a metal ion to determine the concentration of the ion.

Atomised

Turned into individual atoms

Calibration curve

Plots absorbance values concentration of the ion of interest for several standard solutions at a range of concentrations. therefore, the absorbance of the unknown sample can be found using the calibration curve

Basic chemicals

One of the three sectors of the chemical industry.

e.g. Organic and inorganic chemicals, industrial gases, fertilisers and synthetic resins

Specialty chemicals

One of the three sectors of the chemical industry.

e.g. Explosives, paints, rubber products, plastics products, foam products, inks, adhesives, glues and surface cleaners

Consumer chemicals

One of the three chemical sectors.

e.g. Cosmetics and toiletries, soaps and detergents, pesticides, medicinal and pharmaceutical products

Synthesis reaction

Two or more simple substances combine to form a more complex product ( A+ B → AB)

Technical grade

Products used for non-critical laboratory tasks such as rinsing

Synthesis reagent

Suitable for organic synthesis

Analytical reagent

Suitable for quantitative analysis, research and quality control (high purity)

Pharmacopoeia grade

Product has met the purity requirement to be used in the production of pharmaceuticals

Atom economy

Expresses the proportion of reactant atoms that end up in a useful product measuring the number of atoms of the starting materials that end up as products that are wanted and the number that end up as waste.

% _________ = (mass of desired product/total mass of all reactants) *100

the closer to 100, the less the waste

% purity

= (mass of useful product in sample/total mass of sample) *100

green chemistry

the acceptance that the chemical industry must not adversely affect the environment for future generations is the driving force behind the development of ______.

Analytical chemistry

branch of chemistry which deals with the indentification and quantification of substances:

• Qualitative

• Quantitative

Qualitative analytic chemistry

what is present?

Quantitative analytical chemistry

how much is present?

Bromine water test

for unsaturation — used to identify the presence of double or triple bonds

electrophilic species (bromine water is an electrophilic reagent) will add across double or triple bonds.

distinct decolourisation of bromine water (from orange/brown to colourless) of the reagent when unsaturation is present

electrophilic species

electron-loving species

can add across double bonds

Identification of alcohols

have the hydroxyl (OH) group as their primary functional group

Primary and secondary can be oxidised using strong oxidant (e.g. acidified potassium dichromate)

oxidisation by strong oxidant

(potassium dichromate, acidified postassium permanganate)

tests for presence of primary or secondary alcohols

NOTE: aldehydes will also give a positive result

• primary alcohol → aldehyde → carboxylic acid

• secondary alcohol → ketone

orange dichromate ion (Cr₂ O₇^2-) will reduce to the green chromium (II) ion, Cr²⁺

purple permanganate ion (MnO₄ ^-) will reduce to the colourless manganese (II) ion, Mn²⁺

NOTE: tertiary alcohols cannot be oxidised and thus will not change colour to any oxidants

Lucas test

distinguishes between the three classes of alcohols based on the difference in their reactivity with hydrogen halides

• primary alcohols have no visible reaction after several minutes

• secondary alcohols form an oily layer after several minutes

• tertiary alcohols form an oily layer immediately

litmus tests, carbonate, metal tests

tests for carboxylic acids

• as they are acids, they turn blue litmus paper red

• produces CO₂ gas (fizzing) when a carbonate is added

• Hydrogen gas (fizzing) when reacted with sodium or magnesium metal

AgNO₃ (aq) tests on haloalkanes

• Fluoroalkanes do not react

• Chloroalkanes form a white precipitate (AgCl) after several minutes

• Bromoalkanes form a cream precipitate (AgBr) within a minute

• Iodoalkanes form a yellow precipitate (AgI) within seconds

Infrared (IR) spectroscopy

used as a quantitative test of organic compounds to determine the presence of functional groups

wet chemical tests

classical laboratory methods that use liquid solutions, reagents, and basic glassware to identify or measure the amount of a substance

• essentially limited to qualitative investigation

• nature of an organic compound can give misleading results if more than one functional group is present.

they can:

• identify each individual functional group present

• identify the molecular formula of a compound

• distinguish between structural isomers

• analyse mixtures of organic compounds

• quantify the amount of each organic compound present

mass spectrometer

an analytical instrument that identifies and quantifies molecules by converting them into ions and measuring their mass-to-charge ratio

ionisation chamber

here, the sample is bombarded by a high energy electron beam, which knocks a valence electron of the molecule to form a molecular ion (M⁺)

mass analyser

molecular ions are accelerated by an electric field which is curved, then deflected by a magnetic field. ions with different m/z (mass to charge) ratios are deflected to different extents

results in ‘sorting’ of ions according to their mass to charge ratio

detector

detects and quantifies the separated ions, producing a mass spectrum

base peak

most common fragmentation peak (mass spec) - highest relative intensity

parent peak

the signal that represents the complete, unfragmented molecule with a single electron removed (mass spec)

mass spectrometer

plot of relative intensity vs m/z

relative intensity assigns the molecular fragment with the highest abundance - a value of 100

NMR (nuclear magnetic resonance spectroscopy)

technique used to determine a compound’s unique structure

it identifies the carbon-hydrogen framework of an organic compound

• HNMR spectroscopy or proton NMR - analyses the hydrogen-1 nucleus

• CNMR spectroscopy - examines carbon-13 nucleus

magnetic moment

measure of a magnet's overall strength and the direction it tries to point inside an external magnetic field

resonance

the exact moment when an atomic nucleus in a magnetic field absorbs radio-frequency energy and flips its spin state

superconducting magnets

produce a very strong magnetic field

radio frequent (RF) generator

excites the nuclei causing a flip-spin

chemical environment

includes the atom and its surrounding electrons, for a specific atom within a molecule (used in HNMR and CNMR)

electron shielding

the way surrounding electron clouds protect a nucleus from an external magnetic field - reduces the experienced field. since the magnetic field experienced at the nucleus defines the energy between different spin states, it also defines what the chemical shift will be for the nucleus

signal splitting

many single peaks on a low-resolution spectrum will consist of multiple peaks on a high resolution spectrum (HNMR)

the division of a single NMR signal into multiple peaks caused by the magnetic influence of neighboring, non-equivalent nuclei

indicates with the n+1 rule how many hydrogens are on the neighbouring carbon for each environment

n+1 rule

predicts the number of peaks (multiplicity) a signal will split into based on the number of neighboring equivalent protons

e.g. if there are three peaks → the environment has two hydrogens on the neighbouring carbon (2 adjacent hydrogens)

relative peak area

HNMR - tells you how many hydrogens are in the environment that cluster of peaks represents - NOTE: THIS IS A RATIO (between the different environments)

Nomenclature

assigning of a name which uniqely identifies a substance

IUPAC

(International Union of Pure and Applied Chemistry) - systematic organic nomenclature

• systematic rules for naming organic compounds

PIN

designated IUPAC name for each compound, usually uses the systematic naming rules, but occasionally the ___ is an established common name for a familiar compound (e.g. water, ammonia, acetic acid)

Alkane

straight chain of carbon and hydrogen atoms with only single bonds (-ane)

Alkene

if there is a c-c double bond, the chain becomes an alkene (-ene)

Alkyne

if there is a c-c triple bond, the chain becomes an ______ (-yne)

Locants

a number that is inserted into the name right before a functional group, locating it in the chain (functional groups are given the lowest locant number possible)

Vowel Rule (naming organic compounds)

the vowel is dropped if one portion of the name ends in a vowel and the next starts with a vowel (or a ‘y’)

• e.g. ene-3-yne becomes en-3-yne

Commas and dashes (naming organic compounds)

• numbers → numbers uses commas

• letters → numbers / numbers → letters uses dashes

substituents

parts of the molecule that come off the main, “parent” chain

• includes: halogens and alkyl (side chains)

halogens/haloalkanes

any group 7 atom that can take place of any hydrogen in the molecule

• 1st part of name + o

• e.g. Fluoro- Chloro- Bromo- Iodo-

If there is no difference in locants, the substituent that comes first alphabetically is given the lowest locant number ALL SUBSTITUENTS ARE EQUAL

placed at the start of the molecule name

Alkyl/side chains

include any c-c bonds that aren’t part of the parent chain (-yl)

• alkanes: parent chain is decided by length

• If there are double/triple bonds or functional groups, the parent is the longest chain with a double bond etc.

placed at the start of the molecule name (e.g. 2-methyl-)

If there is no difference in locants, the substituent that comes first alphabetically is given the lowest locant number ALL SUBSTITUENTS ARE EQUAL

Functional groups

parts of an organic molecule that affect its physical and chemical properties. They either contain an oxygen or a nitrogen or both, they change the end of the name (the suffix)

alcohols

a hydroxyl group (OH) that is singly bonded to a carbon on the parent chain (-ol)

aldehydes

a carbonyl group (C=O) at terminal end of parent chain (-al)

ketones

a carbonyl group (C=O) that is not on a terminal carbon of parent chain (-one)

carboxylic acids

combination of a carbonyl (C=O) and hydroxyl (OH) group both coming from the same carbon. It can only form on a terminal carbon (-oic acid)