prelim Flashcards
relative abundance
the percentage of that isotope in the naturally occurring element
Isotopes
Atoms of the one element that have different numbers of neutrons in their nuclei. Named by mass number
Prefixes
one - mono two - di three - tri four - tetra five - pent six - hex seven - hept eight - oct nine - non ten - dec
Nomenclature of Covalent Compounds
- more electronegative element last
- last element has suffix -ide
- prefix denoting number of atoms
Nomenclature of Ionic Compounds
- Cation first, anion second
- Monoatomic anions
- suffix ide
Polyatomic anions
- unique names - Cations
- oxidation state for atoms that may have several
Non-metal properties
- solid or gas at room temp
- dull/non-lustrous
- poor conductors
- neither malleable nor ductile
Properties of Metals
- solid at room temp
- shiny, lustrous
- good conductors of heat/electricity
- malleable and ductile
Gravimetric Analysis
- analysis by mass
Heterogenous mixture
composition varies throughout mixture
Emission Spectrum
when an atom has electrons in higher levels that can move down to lower levels, they emit photons with an energy based on the difference in electron levels
- as electrons move, excess energy is emitted as light
Ionisation Energy
The energy required to remove an electron and form an ion
Homogenous mixture
uniform in composition
physical properties - definition
characteristics of a substance that can be observed without changing it into a different substance
Flame Test colours
copper - green calcium - red strontium - red barium - green potassium - purple sodium - yellow (cations cause colour)
Sulphate
(SO4)2-
Hydroxide
(OH)-
Carbonate
(CO3)2-
Sulphite
(SO3)2-
State of Matter - periodicity
solid to gas across a period
Unstable Isotopes
release radiation to become more stable. Atomic number >83
Physical properties to separate mixtures
- filtration
- solubility
- boiling point
- evaporation
- distillation
- density
- sedimentation
- decanting
Characteristics Used to identify substances
- colour
- magnetism
- melting and boiling points
- density
Nitrate
(NO3)-
Nitrite
(NO2)-
Alpha
- helium nucleus
- low penetrative ability
- decays as there are too few neutrons to be stable
Detoxifying Poisonous Foods
Cycad Fruit - leaching - fermentation Black Beans - heat seeds - scrape into finer portions - soak in water - mash then bake
Leaching
- grind/pound kernels
- soak in water
- ground then bake
- salt sometimes used
Fermentation
Stored for months in a moist environment
Beta
- electron
- medium penetrative ability
- decays as there are too many neutrons to be stable
Gamma
- no particle is released, instead electromagnetic radiation
- high penetrative ability
- decays from an unstable atom releasing energy
Phosphate
(PO4)3-
Intermolecular forces
forces that act between molecules
- dipole-dipole
- dispersion
- hydrogen bonding
Intramolecular forces
- forces that act within the molecule
ionic bonding
- atoms exchange electrons to achieve noble gas configuration
covalent bonding
atoms share electrons to gain noble gas configuration
ionic substance properties
- solids at room temp
- high melting and boiling points
- hard and brittle
- don’t conduct electricity as solids
- when molten or in aqueous solution, they do conduct electricity
Covalent molecular substance properties
- generally gases or liquid at room temp
- low melting and boiling points
- soft as solids
- pure covalent don’t conduct electricity
- in aqueous solution do conduct electricity
why do ionic substances have those properties?
- much energy is needed to break up electrostatic forces between ions
- ions are tightly bound and unable to move towards a charged electrode, therefore do not conduct electricity
why do covalent molecular substances have those properties?
- bonding forces holding the atoms together within the molecule are very strong, but intermolecular forces are easily broken, hence lower boiling and melting points
covalent network solids
- covalent bonding extends indefinitely throughout
- don’t conduct electricity except graphite
metallic bonding
- metals all have a common structure
- 3D array of positive ions held together by a mobile ‘sea’ of delocalised electrons
polar covalent bonds
electrons are unequally shared
dipole-dipole forces
the attractive electrostatic forces between polar molecules
dispersion forces
weak intermolecular forces that arise from electrostatic attractions between instantaneous dipoles in neighbouring molecules
hydrogen bonding
type of intermolecular force that involves a hydrogen atom bonded to an O, N or F atom in one molecule becoming attached to an O, N or F atom in a different molecule
Strength of bonds
- intramolecular forces
- hydrogen bonding
- dipole-dipole+dispersion
- dispersion
allotropes
forms of one element that have distinctly different physical properties
law of conservation of mass
matter cannot be created or destroyed, but merely changed from one form to another
relative atomic mass
average mass of the atoms present in the naturally occurring element, relative to the mass of an atom of the carbon-12 isotope
mole
the amount of a substance that contains exactly 6.022x10^23 atoms, molecules or ions
converting between mass and moles
n=m/MM
moles to number of atoms or molecules
N=nxNA
percentage composition in a compound
%A in a compound = mass of A in one mole of compound/mass of one mole of compound
calculating formulae from experimental data
- write down masses of all present elements
- convert masses to moles
- divide by smallest number of moles to get simple ratio
limiting reagent calculations
compare quantities to determine which is in short supply
accuracy of measuring equipment
- measuring cylinders +- 5%
- pipettes and burettes +- 0.2 to 0.5%
- volumetric flasks +- 0.2 to 0.5%
concentration formula
c=n/v
dilution formula
c2v2=c1v1
combined gas law
PV=nRT
gas law assumption 1
gases contain a large number of molecules in random and rapid motion, moving in a straight line until they hit the wall of a container from which they bounce off
gas law assumption 2
the molecules of gas occupy a negligible volume of the container which they are in
gas law assumption 3
the molecules of a gas experience no forces except when they collide with each other and the walls of the container
Gay-Lussac’s Law
P1/T1=P2/T2
Boyle’s Law
P1V1=P2V2
Charles’ Law
V1/T1 = V2/T2
Avogadro’s Law
V1/n1 = V2/n2
indicators of a chemical change
- gas is evolved
- precipitate is formed
- colour change
- significant temperature change
- solid disappears
- an odour is produced
synthesis reaction
A+B –> AB
decomposition
AB –> A+B
combustion
A + O2 –> H2O + CO2
precipitation reaction
A + Soluble Salt B –> Precipitate + Soluble Salt C
Acid Base reaction
Acid + Base –> salt + water
acid carbonate reaction
acid + metal carbonate –> salt + water + carbon dioxide
atomic radius - reactivity
reactivity increases as atomic radius increases
electronegativity - reactivity
reactivity increases as electronegativity decreases
oxidation
the loss of electrons
reduction
the gain of electrons
half equations
describes the oxidation and reduction processes separately in terms of electrons lost or gains
oxidant
- substance that brings about oxidation of another substance
- oxidant gets reduced
reductant
- substance that brings about reduction of another substance
- reductant gets oxidised
oxidation numbers
the oxidation of an element in a molecule or ion is the charge the atom of that element would carry if the molecule or ion were completely ionic
oxidation state - substance in elemental state
oxidation number of zero, regardless of the formula of the molecule
oxidation state - monatomic ion
simply the charge on the ion
oxidation state - fluorine
-1
oxidation state - hydrogen
hydrogen has an oxidation state of +1 except where it is -1
oxidation state - oxygen
oxygen has an oxidation of -2 unless the other rules dictate that it have a different value
oxidation state - chlorine, bromine, iodine
-1 unless other rules require them to have a different value
oxidation state - molecule or ion
the algebraic sum of the oxidation numbers of the elements in a molecule or ion must equal the net charge on the species
increase in oxidation number
corresponds to oxidation
decrease oxidation number
corresponds to reduction
Galvanic cell
a device in which a chemical reaction (redox reaction) occurs in such a way that it generates electricity
electrode
the conductor that connects the external electrical circuit to the solution of the galvanic cell (the pieces of metal)
electrolyte
a substance that in solution or in the molten state conducts electricity (the solution/liquid)
salt bridge
a device that provides electrical contact between solutions in a galvanic cell. allows the migration of ions between two electrolytes in a galvanic cell to maintain electrical neutrality in the cell solutions
Reaction Spontaneity
- if the overall voltage is positive the reaction is spontaneous
- if negative, the reaction is not spontaneous
rate of reaction
the rate at which reactants are used up or the rate at which products form in a chemical reaction
factors influencing the rate of a reaction
- concentration
- temperature
- catalyst
- surface area
factors influencing the rate of a reaction - temp
increasing temperature increases rate of reaction
factors influencing the rate of a reaction - concentration
increasing the concentration increases the rate of reaction
factors influencing the rate of a reaction - catalyst
a substance that increases the rate of reaction without undergoing permanent chemical change in the reaction. catalyst provides alternate lower activation energy
factors influencing the rate of a reaction - surface area
increasing surface area of reactant increases rate of reaction
Activation energy
- an energy barrier between reactants and products
- the higher it is, the harder it is for reactants to get over it and form products, so the slower, the reaction is
collision theory
collision theory proposes that, for a chemical reaction to occur, the reactant particles must
- collide
- have more than a certain minimum amount of kinetic energy
- be correctly orientated
Permanganate
(MnO4)-
Hydrogencarbonate
(HCO3)-
Dichromate
(Cr2O7)2-
Chromate
(CrO4)2-
Ammonium
(NH4)+
Cyanide
(CN)-
peroxide
O2 2-
methane
CH4
