all chemistry definitions

reversible reaction

one in which the products react to give back the reactants

chemical equilibrium

state of dynamic balance in a reversible reaction where the rate of the forward reaction is the same as the rate of the backward reaction

dynamic state

the reactants are continuously forming products and the products are continuously forming reactants

dynamic equilibrium

the rate of the forward reaction is equal to the rate of the backward reaction

le chatelier’s principle

if a stress is applied to a system at equilibrium, the system re-adjusts to relieve the stress applied

what does le chatelier’s principle predict about all gaseous reactions

an increase in pressure will favour the reaction the brings about a reduction in volume (side with smaller number of molecules)

haber process

manufacturing of ammonia at high pressure and low temperature

what catalyst is used in the haber process

iron

contact process

manufacturing of sulfuric acid at compromise temperature and just above atmospheric pressure

chemical equilibrium is affected by —— and not affected by

temperature, pressure

organic chemistry

the study of the compounds of carbon

hydrocarbon

a compound that contains only carbon and hydrogen

what are the hydrocarbon families

alkanes alkenes alkynes

saturated compound

there are only single bonds between the atoms in the molecule

order of formula names in organic chem

meth eth prop but hept hex sept oct non dec

properties of a homologous series

similar chemical properties, showing gradations in physical properties, general formula, similar method of prep, each differing from prior by a unit

structural isomers

compounds with the same molecular formula but different structural formulas

unsaturated compound

contains one or more double or triple bonds between atoms in the molecule

tests for unsaturation, and colour change if unsaturation present

bromine water (red to colourless), potassium permanganate (purple to colourless)

aliphatic compound

organic compound consists of open chains of carbon atoms and closed chain compounds that resemble them in chemical properties

aromatic compounds

what is used to separate the components of crude oil

fractional distillation

fractions of crude oil listed from lowest bp up

petroleum gas, petrol, naphtha, kerosene, diesel oil, lubricating oil, fuel oil, bitumen

auto ignition

premature ignition of the petrol-air mix before normal ignition by spark can take place

octane number

measure of the tendency of the fuel to resist knocking

what 2 hydrocarbons help define the octane number scale

heptane and 2,2,4-trimethylpentane

factors affecting octane number

length of chain, degree of branching, straight or cyclical

methods to change octane number

catalytic cracking, isomerisation, addition of oxygenates, dehyrdrocyclisation

heat of reaction

heat change when the numbers of moles of reactants indicated in the balanced equation for the reaction react completely

heat of combustion

heat change when one mole of the substance is completely burned in excess oxygen

kilogram calorific value

the heat energy produced when 1kg of the fuel is completely burned in oxygen

bond energy

average energy required to break one mole of a particular covalent bond to separate the neutral atoms completely from each other

heat of neutralisation

heat change when one mole of h+ ions from an acid react with one mole of oh- ions from a base

heat given out formula

mass x specific heat capacity x temperature rise

heat of formation

heat change that takes place when one mole of a compound in its standard state is formed from its elements in their standard states

hess’s law

if a chemical reaction takes place in a number of stages, the sum of the heat changes in the separate stages is equal to the heat change if the reaction is carried out in one stage

law of conservation of energy

energy cannot be created or destroyed, only converted

energy level

fixed energy value that an electron in an atom may have

ground state

electrons are occupying the lowest available energy level

excited state

where electrons occupy higher energy levels than those available in ground state

heisenberg’s uncertainty principle

its impossible to measure the velocity and position of an electron at the same time

orbital

region of space that there is a high probability of finding an electron

sublevel

subdivision of a main energy level consisting of one or more orbitals of the same energy

limits of Bohr’s theory

failed to account for many of the lines in the emission spectra of atoms larger than hydrogen, didnt account for wave motion, heisenberg principle didnt align, couldnt explain splitting of certain lines in emission spectra (sublevels)

element

a substance that cannot be split into simpler substances by chemical means

who came up with triads

dobereiner

who came up with octaves

newlands

who came up with the modern periodic table

mendeleev

what did mendeleev do in his table that was unique to newlands

left gaps and prioritised properties over weight

atomic number

the number of protons in the nucleus of that atom

mass number of an element

sum of the number of protons and neutrons in the nucleus

isotopes

atoms of the same element (atomic number) with differing mass numbers due to different number of neutrons in the nucleus

relative atomic mass

the average of the mass numbers of the isotopes of the element as they occur naturally taking their abundance into account and expressed on a scale in which the atoms of the carbon-12 isotopes have a mass of exactly 12 units

principle of mass spectrometry

charged particles moving in a magnetic field are deflected to different extents according to their masses and thus are separated by mass

stages of mass spectrometry

vaporisation, ionisation, acceleration, separation in a magnetic field, detection

what is mass spectrometry used for

identify isotopes, measure relative abundance of isotopes, identify unknown compounds

electron configuration

shows arrangement of electrons in an atom of an element

aufbau principle

when building up the electron configuration of an atom in its ground state, the electrons occupy the lowest available energy levels

hunds rule of maximum multiplicity

when 2 or more orbitals of equal energy are available, the electrons occupy them singly before filling them in pairs

quantisation

electrons can only have certain levels of energy

what series of emission spectrum is visible to the human eye (jumps to n=3)

balmer

formula for light emitted in bohrs (plancks constant)

e2-e1=hf

pauli’s excllusion principle

no more than 2 electrons may occupy an orbital and they must have opposite spins

a compound

a substance that is made up of two or more different elements combined together chemically

octet rule

when bonding occurs, atoms tend to reach an electron arrangement with 8 electrons in the outermost energy level

what dont usually obey the octet rule

transition metals, hydrogen, lithium, beryllium

ion

a charged atom or group of atoms

negative ions

anions

positive ions

cations

ionic bond

force of attraction between oppositely charged ions in a compound. always formed by the complete transfer of electrons from one atom to another

what diagram is used to show ionic bonding

dot and cross

three dimensional arrangement of ions

crystal lattice

what are ionic bonds usually formed between

metals and non metals

what set of stairs divides metals from non metals

boron to astatine

metals have a tendency to —- electrons

lose

non metals have a tendency to —- electrons

gain

typical ion formation of the elements (In order of group I, II, III, IV, V, VI, VII)

+, 2+, none/3+, none, 3-, 2-, -

hydroxide ion

OH-

nitrate ion

NO3-

hydrogencarbonate ion

HCO3-

Permanganate ion

MnO4-

carbonate ion

CO3-2

chromate ion

CrO4-2

dichromate ion

Cr2o7-2

sulfate ion

SO4-2

sulfite ion

SO3-2

thiosulfate ion

S2O3-2

phosphate ion

PO4-3

ammonium ion

NH4+

transition metal

forms at least one ion with a partially filled d sublevel

molecule

group of atoms joined together, the smallest particle of an element or compound that can exist independently

valency

the number of atoms of hydrogen or any other monovalent element with which each atom of the element combines

sigma bond

formed by head on overlap of two orbitals

pi bond

formed by sideways overlap of p orbitals

ionic compound properties

difficult to cut, high melting points, conduct electricity dissolved in water

covalent compound properties

soft, low boiling points, dont conduct electricity

why do transition metals have variable valency

little energy difference between 4s and 3d sublevels means they can lose different numbers of electrons

ending for a compound with ONLY oxygen and one other element

ide

ending of a compound with oxygen and 2 other elements

ate

2 covalent bonds no lone pairs shape

linear