Studied by 16 people
Atom Economy
The amount of atoms 'wasted' when making a chemical. It is the ratio between the amount of atoms (materials, solvents,...) used to the amount of final product obtained.
Activation energy
The minimum amount of energy required for a chemical reaction to proceed
Allotropes
Different physical forms of an element.
Amphiprotic
A specie that can donate and accept a proton
Amphoteric
A compound that can act as a base or an acid
Atomic number
Number of protons an element has
Bond enthalpy
Amount of energy required to break one mole of a certain bond in the gas state!
Bronsted Lowry acid
An acid that can donate a proton to a base
Bronsted Lowry base
A base that can accept a proton from an acid
Buffer solution
A solution that will not ( or very slightly ) change ph when small amounts of acid or base are added to it. They are made up of a weak acid, its salt and a strong base.
Catalyst
Compound/element that will speed up a reaction without getting used up in the process. It does this by providing an alternate path with lower activation energy for the reaction
ـHL: Complex ion
A compound in which molecules or ions form coordinate bonds to a metal or ion
Conjugate acid/base pair and species
Species that differ only by one hydrogen
_HL: Coordination compound
A compound in which coordination bonds
Covalent bonding
When two elements share a pair of elections. As a result, this sharing attracts the nuclei of each element.
Dative bond
A covalent bond where both electrons come from one element
Electron affinity
The energy change when an atom/molecule gains an electron, in the gas state, and per one mole of it
Electron domain or charge center
The number of places (domains) one or more electron are.
Electronegativity
A measure of the tendency of an atom to attract a bonding pair of electrons.
_HL: Electrophile
A specie that can accept an electron pair
Empirical formula
The smallest ratio of elements in a compound
_HL: Enantiomers
Two compounds which have the same chemical formula, but have mirrored displayed formula. Hence displaying opposite optical activity
Enthalpy of formation
The energy needed to form one mole of a compound from its pure elements in their standard states
Equilibrium expression and constant
Ratio of the concentrations of the products over the reactants. This means that a reaction with a kc>>1 will have more products than reactants in equilibrium, one where kc≃1 there will be approximately as many reactants as products in the equilibrium and one where kc<<1 will have more reactants than products in equilibrium.
First ionization energy
Amount of energy required to remove one mole of an outer electrons from one mole of gaseous atoms
_HL: Formal charge
The charge give to an atom has when in a molecule assuming that each chemical bond are shared equally between atoms. Formal Charge = [# of valence electrons on atom] - [non-bonded electrons + number of bonds].
_HL: Free Gibbs Energy
A number that tells us if a reaction is spontaneous (if negative) or not (if positive)
Group
Vertical columns in the periodic table, each element in the same group will have the same number of valence electrons
Half-life
Amount of time needed for a radioactive element to lose half of its activity, the concept also applies to other first-order chemical reactions
Homologous series
Compounds that have the same functional group, similar physical chemical properties and 'increasing' physical properties.
HL_Hybridization
When two orbitals of the same level mix to form a new orbital.
Index of Hydrogen Deficiency
A way to calculate how many double, triple bonds and cycles a hydrocarbon will have
Ionic bonding
When one or more electrons are given from one element to another. This creates two oppositely charged ions that will be attracted to one another because of electrostatic attraction
Isomers
Elements with the same chemical formula but different displayed formulas
Isotopes
Elements with the same number of protons and electrons but a different number of neutrons
_HL: Lattice enthalpy
The energy change when 1 mole of an ionic compound is formed in its gaseous ions
Le Châtelier's Principle
When an equilibrium undergoes a change in conditions (temperature, pressure...) the equilibrium will shift to reduce the effect of that change
_HL: Lewis acid
A compound that can accept an electron pair
_HL: Lewis base
A compound that can donate an electron pair
_HL:Ligand
An ion/molecule that donates a pair of electrons to a metal to form a coordination compound
Line spectrum
A spectrum made of lines. An absorption line spectrum will show the wavelength of light a specie will absorb and an emission line spectrum will show the wavelengths of light the specie emits
_HL: Markovnikov's rule
When hydrogen halides add to asymmetric alkenes two different products can be made. This rule states that the hydrogen will add to the carbon atom that contains the most hydrogen atoms bonded to it.
Mass number
Number of nucleons in an element
Metallic bonding
Bonding of metals, positive ions in a sea of delocalized electrons
Metalloid
A non-metal that shows metal properties
_HL: Molecularity of reaction
The number of molecules in a reaction
Nucleophile
A specie that can give out an electron pair.
_HL: Optical isomerism
Two compounds which have the same chemical formula, but have mirrored displayed formula.
_HL: Optically active carbon
A carbon that will have four different species attached to it
_HL: Order of reaction
To what power the concentration of each reactant depends on the reaction rate
Period
Horizontal row in the periodic table, elements in the same period will have the same number of occupied orbitals
_HL: pi bond
When two p orbitals are parallel to each other and overlap
_HL: Polydentate ligand
A ligand that will have multiple atoms to bonded to a central metal atom or ion. EDTA has 6 for example.
Precision vs accuracy
Accuracy is being able to get values close to the accepted value whereas precision is having many results which are close to each other.
_HL: Racemic mixture
It is when the products of a reaction are enantiomers, and half of the molecules are one enantiomer and the other half is the other.
Rate determining step
The slowest step in a reaction
Rate of reaction
The change of concentration of reactants or products over time
Relative atomic mass
The average number of neutrons and protons in an element/compound
_HL: Sigma bond
When there is an axial overlap between two orbitals
_HL: Standard Hydrogen Electrode (SHE)
The apparatus used to measure the electric potential of species. Made up of a platinum electrode with hydrogen bubbles exposed on the electrode. That electrode is assigned the 0 value for referencing the others.
_HL: Stereoisomerism
Compounds that have the same molecular formula but different arrangement of atoms in space
_HL: TMS reference in 1H NMR
Tetramethylsilane, the standard compound used in 1H NMR with the compounds that are being tested. It is used for calibrating the 1H NMR apparatus and can easily be removed due to its high volatility. It also has 12 identical Hs, meaning little is needed, plus it has a signal on the low side of most other Hs.
Energy Density Equation
energy released from fuel/ volume of fuel consumed
Energy Density definition and units
The energy produced per unit volume. kJcm-3
Specific Energy Equation
energy released from fuel/ mass of fuel consumed
Specific Energy definition and units
the energy produced per unit mass. kJg-1
What does nuclear energy have over fossil fuels
Nuclear fuels have a higher density and specific energy than fossil fuels
Efficiency Equation
useful output energy/ total input energy X 100
What is a fuel?
A substance that can release energy by changing its chemical or nuclear structure
Renewable Energy
A renewable source is one that is replenished at a faster rate than it is used
Examples of renewable energy
Wood, water, tidal power, solar power, geothermal power, biomass, natural gas
Conservation of energy states that:
energy cannot be created or destroyed. It can only be converted from one form into another.
What is inevitable?
In any cyclical process designed to convert heat to work, some energy is always degraded. Degraded energy is energy that is no longer available for the performance of useful work. Heat is transferred to its surroundings. Energy and materials go from a concentrated into a dispersed form.
An Energy source needs to be:
cheap, plentiful, and readily accessible and provide high-quality energy at a suitable rate- not too fast and not too slow. It should do this in a way that has minimal effect on the environment.
A useful energy source
releases energy at a reasonable rate and produces minimal pollution
Non-Renewable Energy
they are used at a faster rate than they can be replenished
examples of non-renewable energies
uranium,
Enthalpy change of combustion
The enthalpy change that occurs when one mole of the substance is burnt completely in an excess of oxygen under standard conditions
Summarise S.E trends in Nuclear, fossil fuels and renewable sources
Nuclear fuels have the highest specific energies and fossil fuels have higher specific energies than the related renewable sources.
Relationship of primary source with secondary source
A primary source of energy is is often not used directly but converted to a secondary source such as electricity and some energy is inevitably lost during the conversion.
Fossil fuels
formed by the reduction of biological compounds that contain carbon, hydrogen, sulfur, nitrogen and oxygen.
Petroleum
a complex mixture of hydrocarbons that can be split by physical process into different component parts, called fractions by fractional distillation
How can the performance of hydrocarbons as fuels be improved?
By the cracking and catalytic reforming reactions
Coal Gasification and Liquefaction
Are chemical processes that convert coal to gaseous and liquid hydrocarbons
A Carbon Footprint Definition
Is the total amount of greenhouse gases produced during human activities. It is generally expressed in equivalent tons of carbon dioxide.
How are fossil fuels made?
Produced by the slow and partial decomposition of plant and animal matter that is trapped in the absence of air.
Formation of anthracite
Anthracite is formed under conditions of very high heat and pressure and is almost pure carbon, but coal generally contains between 80% and 90% carbon by mass.
Advantages of coal
Coal is the most abundant fossil fuel and has high specific energy and energy density
Disadvantages of coal
Difficult and expensive to mine and transport. Produces sulfur oxides, which lead to acid deposition. Particulates which lead to global dimming. Carbon dioxide, a greenhouse gas which leads to global warming.
Crude Oil
A complex mixture of straight-chain and branched-chain saturated alkanes, cycloalkanes, and aromatic compounds. In smaller quantities, compounds of nitrogen, oxygen, and sulfur.
How to make crude oil useful?
Crude oil needs to be refined before it is used as a fuel. Sulfur impurities, must first be removed by dissolving hydrogen sulfide in a basic potassium carbon solution.
Removal of sulfur impurities equation
H2s(g) + CO32- >< HS-(aq) + HCO3-
Recovery of hydrogen sulfide reverse reaction
2H2S(g)+3O2(g)>2SO2(g)+H20(l)
Reaction of sulfur dioxide to produce elemental sulfur
2H2S(g)+SO2(g)>3S(s)+2H20(l)
Fractional Distillation
Crude oil is heated to a temperature of about 400 degrees. The components of the mixture are vaporised and allowed to pass up a distillation column. This allows the crude oil to be seperated into different fractions on the basis of their boiling points.
Refinery Gas Levels and Size of molecules
The level at which molecules condense depends on their size. The smaller molecules containing 1-4 carbon atoms collect at the top. Molecules of successively larger molecular mass condense at lower levels.
Vacuum Distillation
Vaporise residue from hydrocarbons with high boiling points under normal atmospheric conditions and can hence separate them at relatively low temperatures.
Cracking
Breaks down large alkanes to smaller alkanes and alkenes
Thermal Cracking
When the process of cracking is achieved by heating the starting materials
Catalytic Cracking
produces branched-chain alkanes and compounds which contain the benzene ring, which burn more evenly in a car engine than their straight-chain isomers.
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