CHEMISTRY SEMESTER2 EXAM Flashcards
Relative Atomic Mass
Ar = (%a × Ar(a) +%b × Ar(b))/100
Structural formulas
Meth………1 carbon atom Eth…………2 carbon atoms Prop……….3 carbon atoms But…………4 carbon atoms Pent………..5 carbon atoms Hex…………6 carbon atoms Hept……….7 carbon atoms Oct………….8 carbon atoms Non…………9 carbon atoms Dec…………10 carbon atoms
Polarity/Non-Polarity
− Polar molecules: those with slight positive and slight negative charged ends. HAVE NET DIPOLE
− Occurs in all molecules with a single bond dipole
− Non-polar molecules: those where the bond dipoles are of equal size and act in symmetrically opposing directions where the dipoles cancel each other out. HAVE ZERO NET DIPOLE
Mass/Volume/Concentration
c=n/v
Properties of water
− Consists of small molecules with weak dispersion forces
− Strong polarity and extensive capacity of hydrogen bonding dictate its physical properties
− HIGH MELTING POINT (compared to other molecules of similar size); due to extensive hydrogen bonding with neighbouring molecules
− DENSITY IN THE SOLID PHASE IS LESS THAN IN LIQUID PHASE which is why ice floats; undergoes expansion
− Ice floating on water acts as an insulator
− Occurs because each water molecule forms four hydrogen bonds with four neighbouring water molecules
− HIGH SURFACE TENSION (liquids tendency to resist any increase in its surface area); results from strong intermolecular forces
− At water surface there is an imbalance of these forces causing molecules to be pulled in towards the bulk material
− Surface is trying to contract and achieve a minimum area
Trends In The Periodic Table
ATOMIC RADIUS
− Decreases from left to right (due to increasing nuclear charge and electrons are pulled closer to the nucleus)
− Increases down any group (as you go down a group the number of electron shells increases)
Trends In The Periodic Table
FIRST IONISATION ENERGY
a measure of how strongly it an atom holds onto its electrons
− Increases from left to right (due to the atom wanting to hold onto its electrons)
− Decreases down any group (as atomic radius gets bigger there is a further distance between electron and nucleus, thus weaker attraction)
Trends In The Periodic Table
ELECTRONEGATIVITY
ability of an atom in a molecule to attract electrons to itself
− Increases from left to right (due to the atom wanting to gain electrons)
− Decreases down any group
Addition reactions of hydrocarbons
− ONLY ALKENES UNDERGO ADDITION
− Double bond is replaced by bonds to other atoms such as H, F, Cl, Br or I
− Reagents used are H2, Cl2, Br2, HCl and HI
EXAMPLE
CH2=CHCH2CH2CH2CH3 + Br2 -> CH2BrCHBrCH2CH2CH2CH3
Substitution reactions of hydrocarbons
− Occur when alkane or benzene is combined with Cl2 or Br2
− Replacement of one of more H atoms with Cl or Br atoms
EXAMPLE
CH3CH3 + Br2 -> CH3CH2Br + HBr
Saturated
− An SATURATED solution contains as much solute as it can normally dissolve
Unsaturated
− An UNSATURATED solution contains less solute than it is able to dissolve
Supersaturated
− An SUPERSATURATED solution contains more solute than is can normally dissolve
KINETIC THEORY
− Particles of a gas are in rapid continuous random motion
− Attraction and repulsion between particles in a gas is negligible
− Total volume of all particles is negligible compared to volume the gas occupies
− Have kinetic energy
− Average kinetic energy of particles of a gas is proportional to its temperature
− Particle collisions are elastic and do not lose speed or slow down
KINETIC THEORY APPLIED TO REAL GASES
− Ideal gas has negligible volume, real gases do occupy space and volume is significant
− Ideal gas has negligible attraction, real gases do have forces of attraction and are significant
UNIVERSAL INDICATOR
− pH 0-3 = red − pH 4-6 = orange/yellow − pH 7 = green − pH 8-10 = blue − pH 11-14 = purple
METHYL VIOLET
− Acid colour = Yellow
− Base colour = Blue
BROMOCRESOL PURPLE
− Acid colour = Yellow
− Base colour = Violet
THYMOLPHTHALEIN
− Acid colour = Colourless
− Base colour = Blue
Chromatography
− A multi-step process used to separate and/or analyse the different components or solutes of a mixture or substance, whether it be liquid or gas, without causing any molecular changes to the chemicals involved
STATIONARY PHASE
− Solid or thick liquid
− Remains in fixed position
MOBILE PHASE
− Liquid or gas
− Carries components through or across stationary phase
Absorption
− Fluid is dissolved by a liquid or sold
− Endothermic
− Not affected by temperature
− Concentration uniform
ADSORPTION
− Atoms, ions or molecules of a substance adhere to the surface of the absorbent
− Exothermic
− Preferred at low temperature
− Concentration on surface is different from inside
Paper chromatography
− Used to separate coloured chemicals or substances
− STATIONARY PHASE: Paper
− MOBILE PHASE: aqueous liquid or non-aqueous solvent
− Ink is added to the bottom of the paper and placed in the solvent which uses capillary action to pull it up the paper and separate each component depending on polarity
− How far the components are moved up the paper depends on the ability to be absorbed into the paper vs ability to be carried along
− More polar components absorb more quickly as paper is polar
Thin-layer Chromatography
− Analysing mixtures
− STATIONARY PHASE: thin glass plate coated in silica or alumina
− MOBILE PHASE: solvent chosen on polarity
− Small amount of solution added to the end of TLC place which is then placed in the mobile phase which uses capillary action to pull it up the glass and separates each component depending on polarity
− Substances that aren’t visible are coated and shone under UV light or placed in iodine
− SHARPER AND MORE DEFINED THAT PAPER CHROMATOGRAPHY
− SIMPLE AND INEXPENSIVE
− ONLY SMALL AMOUNT OF SAMPLE NEEDED
Gas Chromatography
− Ability to identify individual substances of a mixture and their concentrations
− STATIONARY PHASE: high boiling point non-volatile viscous liquid, which has been coated in silica
− MOBILE PHASE: inert carrier gas
− Sample is dissolved and vaporised in a vaporisation chamber via syringe
− Flows along carrier gas stream into chromatography column
− Components with high volatility stay in mobile phase and leave quicker and have lower retention time
− At the end a detector records a chromatograph
High Performance Liquid Chromatography
− Best suited for substances that decompose when heated or cannot be vaporised
− STATIONARY PHASE: tightly packed column of fine particles such as silicon dioxide
− MOBILE PHASE: liquid solvent
− Sample is injected into high-pressure column containing the solvent where it travels through a chromatography column where the mixture is separated
− Detector created chromatograph
NORMAL PHASE HPLC
− Filled with silica particles and non-polar solvent (polar components will attach to silica molecules longer that non-polar)
REVERSE PHASE HPLC
− Silica is non-polar due to attachment of hydrocarbon and polar solvent
Percentage mass
% element in compound= (mass of element in sample)/(total mass of sample)×100
Electron Configuration
1st shell = 2 electrons
2nd shell = 8 electrons
3rd shell = 8 electrons
4th shell = 2 electrons
JOHN DALTION
− Atomic theory:
Elements are composed of extremely small particles
All atoms of a given element are identical
Atoms are not created nor destroyed or changed
Chemical reaction involves only separation, combination, rearrangement of atoms
Compounds are formed when atoms of more than one element combine in a specific ration
J.J. THOMSON
− Plum pudding model (electrons embedded in the nucleus)
− Discovered the electron
− Electrons have a mass 1/1000th of the smallest atom known