unit 1 - FOCUS Flashcards
content i need to REVISE (weaknesses)
oxalate
C2O4 -
atomic absorption spectra
element-specific frequencies of electromagnetic radiation at which energy is absorbed when transitioning up from a ground to excited state, represented as a continuous spectrum of light with specific frequencies of light missing (black lines = gaps between energy levels, absorbed by the atom)
atomic emission spectra
element-specific frequencies of electromagnetic radiation at which energy is emmited when transitioning down from an excited to ground state, represented as specific frequencies of light (coloured lines on a black background = gaps between energy levels, emitted by the atom)
purpose of monochromator
unabsorbed light is focued through a slit, entering a monochromator that separates into specific frequencies and distinguishes wavelengths of interest
water of crystallisation
water chemically bonded into a crystal structure of ionic salts (completely embedded as full H2O molecule between lattice gaps)
hydrous salts
contain water of crystallisation
quantum dots (what are the compounds)
ZnS, ZnSe, CdSe
quantum dots (functions)
emit size-dependent wavelengths of light (small = violet, large = red)
used as a biological tracer due to fluorescent microscopy/photometry
dispersion forces (how do they arise)
arise in all substances, since electrons are constantly moving, and thus not always symmetrically distributed, resulting in a very temporary/momentary, weak “instantaneous dipole”
factors that influence dispersion forces
surface area, mass, number of atoms
how does surface area influence dispersion forces
larger surface area => ability of increased proximity between molecules => stronger forces
how does mass influence dispersion forces
heavier (more protons) => more electrons => more chance/likelihood AND increased strength of an instantaneous dipole
how does number of atoms influence dispersion forces
increased proximity / concentration
more electrons => more chance/likelihood of instantaneous dipole
what are dipole-dipole forces
interactions between polar molecules with a partial charge, specifically electrostatic attraction (and repulsion) between physically aligned covalent molecules experiencing temporary, relatively weak, Dipole Moment
factors that influence dipole-dipole forces
molecular dipole, size, surface area
how does molecular dipole influence dipole-dipole forces
stronger individual dipole => stronger electrostatic attraction => stronger overall dipole-dipole force
how does size influence dipole-dipole forces
larger molecule => more electrons => more chance AND increased strength of dipole => stronger electrostatic attraction => stronger force
how does surface area influence dipole-dipole forces
increased proximity => increased physical alignment => stronger electrostatic attraction (by inverse square law) => stronger forces
factors that influence hydrogen bonding
atomic radius (inversely)
how does atomic radius influence hydrogen bonding
smaller atomic radius => electrons confined to a smaller space => increased density => stronger, condensed partial charge => stronger polarity => stronger hydrogen bonding
factors that overall impact intermolecular forces
atomic radius, mass, surface area, number of electrons, size, molecular dipole strength
how do intermolecular forces influence MP / BP
stronger intermolecular forces => more energy required to overcome electrostatic attraction and intermolecular forces => increased kinetic energy needed => higher melting and boiling point temperatures
vapour pressure
tendency of a substance to evaporate
how do intermolecular forces influence vapour pressure
weaker intermolecular forces => lower boiling points => increased vapour pressure and increased volatility
pure substance
substances made of one type of moelcule with a FIXED / CONSTANT / UNIFORM COMPOSITION, AS WELL AS WELL DEFINED, CONSTANT PHYSICAL AND CHEMICAL PROPERTIES
surface tension
measure of forces required to strecth or break the surface of a liquid, due to strong cohesive forces (hydrogen bonds)
dissociation
ionic substance dissolving into separate, independent mobile ions
ionisation
molecule splitting into individual ions, i.e. formation of charges
ion-dipole forces
attraction between fully-charged ion and partically-charged dipole, occuring in all forms of dissolution between formed ions and water
relationship between solubility of solids and temperature
more kinetic energy => particles able to move more => weakened intermolecular forces => can be overcome with less additional energy => dissociates and ionises more
relationship between solubility of gases and temperature
more kinetic energy => particles able to move more => weakened intermolecular forces => more difficult to be “held” by solvent => “escapes” the surface of the solvent
types of water pollution
sweage, disease causing aagents, sediment pollution, inorganic plant and algal nutrients, organic compounds, inorganic compounds, radioactive substances, thermal pollution
factors of intermolecular forces that influence chromatography
types and charges of polar groups, molecular weight, molecular geometry
how does the type and charge of polar groups influence chromatography
molecules preferentially bond with phase having the most similar bonding TYPE (thus the amount of same polar groups as well)
how does molecular weight influence chromatography
heavier => larger => more likely to bond with stationary phase and remain in it longer => reduced Rf and increased Rt
how does molecular geometry influence chromatography
greater surface area => more likely to bond with stationary phase and remain in it longer => reduced Rf and increased Rt
normal phase
stationary POLAR, mobile NONPOLAR
reverse phase
stationary NONPOLAR, mobile POLAR
mobile phase in PC
solvent (water) progressing along the stationary phase (filter paper) due to capillary action (combination of cohesion and adhesion)
advantages of TLC over PC
glass plate is more rigid than flexible paper; easier to control
after separation, substances can easily be recovered
