Chapter 1, 2, & 3 Flashcards
define enrichment
separation of isotopes
why is fluorine weird?
it only has 1 naturally occurring isotope
what is the Bohr model?
- electrons can occupy DISCRETE energy levels within atom
- can transition b/w these energy levels by ABSORBING or EMITTING EXACTT amounts of energy
define atomic orbital
region of space where there is a high probability of finding an electron
Pauli exclusion principle says . . .
2 electrons can only occupy the same atomic orbital if they have OPPOSITE spins
Aufbau principle says . . .
electrons fill atomic orbitals of lowest energy first - atomic orbitals within a sublevel (e.g. the 3 orbitals in 2p sublevel) are DEGENERATE
exceptions are Cr & Cu
define degenerate
equal energy
which has higher energy, 4s or 3d?
3d
where are electrons removed from first?
4s orbital is further away from the nucleus than 3d so electrons are removed from the furthest shell first
Hunds rule says . . .
electrons fill orbitals in same sub-level singly before pairing up
define wavelength
distance b/w 2 crests in oscillating wave
define frequency
of waves that pass a point in 1 second
order of decreasing wavelength (increasing energy)
radio>microwaves>IR>VIS>UV>X-rays>Gamma
continuous spectrum?
all wavelengths + frequencies of visible light are shown
continuous spectrum?
all wavelengths + frequencies of visible light are shown
line spectrum?
some wavelengths are missing
difference b/w absorption & emission line spectrum
ABSORPTION = ALL COLOURS, black streaks
EMISSION SPECTRUM = BLACK, colorful streaks (black EMU wearing COLORFUL sunglasses)
The longer the arrow in a hydrogen emission spectrum . . .
the greater the amount of energy that is emitted
how does an emission line spectrum form?
- high voltage passed through gas
- electrons become excited
- transition to higher energy levels
- as electrons fall back down to lower energy levels, transitions accompanied by emission of energy in the FORM OF PHOTONS
- the energy released by different elements corresponds to dif wavelengths within the visible light range of EM radiation
Briefly explain how a mass spectrometer works
- used to determine relative atomic masses + organic structure
- sample is vaporised
- bombarded w/ high energy electrons
- produces + ions
- accelerated in electric field
- cations DEFLECTED in magnetic field
- depending on mass / charge ratio
higher mass to charge ratio = ?
LESS DEFLECTION
which is deflected more, 79Br2+ or 91Br+ ?
79Br2+ since it has the LOWER m/z ratio
Solids?
- particles closely packed
- strong forces b/w particles
- vibrate about fixed positions
- fixed shape + volume
Liquids?
- slightly more spread out
- weaker forces b/w particles
- can move past each other
- take shape of container
- fixed volume
Gases?
- particles very spread out
- negligible forces
- no fixed shape / volume
sublimation
from SOLID to gas
e.g. iodine or solid CO2
depostion
from GAS to solid
difference b/w boiling & evaporation?
- BOILING = occurs at specific temp & takes place throughout the liquid
- EVAPORATION = only takes place at surface of liquid and can occur at temp. BELOW the boiling point
mixtures
contain 2 or more substances mixed together
- NOT chemically bonded
- mixed in ANY proportion
- can be separated by PHYSICAL meanss
heterogenous vs homogenous mixture
- homogenous = only 1 phase, uniform composition throughout
- heterogenous = more than 1 phase, non-uniform composition
immiscible
describes 2 liquids that form a heterogenous mixture
define average atomic mass (Ar)
average of the masses of the isotopes in a naturally occurring sample of the element relative to the mass of 1/12 of an atom of C-12
relative molecular mass
the sum of the relative atomic masses of the individual atoms making up a molecule
relative formula mass
(used for ions) the mass of one formula unit relative to the mass of 1/12 of an atom of C-12
define empirical formula
the simplest whole number ratio of the elements present in a compound
percentage yield = ?
(actual yield / theoretical yield) x 100
What is Avogadro’s law?
equal VOLUMES of gases at the same temperature & pressure contain the same NUMBER OF PARTICLE
what is constant in avogadro’s law?
pressure
temperature
When do gases deviate most from ideal behaviour?
at HIGH PRESSURE
at LOW TEMPERATURE
hplt = hajar paints leo’s teeth
Properties of an ideal gas
- particles are in CONSTANT, RANDOM, STRAIGHT-LINE MOTION
- collisions b/w particles of an ideal gas are elastic (total kinetic energy conserved)
- volume occupied by gas is NEGLIGIBLE relative to vol of container
- NOT INTERMOLECULAR FORCES
- average kinetic energy of particles is DIRECTLY proportional to ABSOLUTE TEMP. IN KELVIN
Why is value pf PV/nRT LESS THAN 1 at moderately high pressures?
because of the effects of intermolecular forces
Why is value of PV/nRT GREATER THAN 1 at very high pressures?
because of the effects of MOLECULAR VOLUME
formula for moles when dealing with molar volume
n = V / Mv
Mv = 22.7 dm^3 mol-1
Boyle’s law
VOLUME is INVERSELY PROPORTIONAL to PRESSURE
(downward CURVE)
Charles’s Law
- VOLUME is DIRECTLY PROPORTIONAL to TEMPERATURE in kelvin
Gay-Lussac’s Law
PRESSURE is DIRECTLY PROPORTIONAL to ASBOLUTE TEMPERATURE
Use Pa with ??
m^3
Use kPa with ??
dm^3
formula for concentration in ppm?
mass of solute (g)) / mass of solution (g) x 10^6
1 ppm = ?
1 mg/ L
difference b/w hydrated & anhydrous?
hydrated = contain water of crystallisation
anhydrous = have lost their water of crystallisation
Experimental determination of empirical formula
- coil of Mg ribbon placed in pre-weighed crucible
- mass is recorded
- crucible placed on a clay triangle
- heated
- when Mg ribbon starts to burn the lid is lifted slightly to allow more air to enter
- heating is continued until all Mg has burned
- after cooling the crucible, its lid & content are reweighed
properties of chemical reactions
- new substances are formed
- bonds in reactants are broken
- bonds in products are formed –> energy change
- fixed relationship b/w # of particles of reactants & products resulting in NO OVERALL change in mass
what is a standard solution?
a solution of KNOWN concentration
where is the burette reading taken from?
the bottom of the meniscus
define atom economy
increasing the conversion efficiency of a chemical process
- a measure of the amount of starting materials that become useful products
what does a high atom economy mean?
fewer natural resources are used & less waste is created
atom economy formula
(total mass of DESIRED product) / (total mass of ALL products) x 100
Outline the use of radioactive isotopes
- isotopes are radioactive as the nuclei of these atoms break down spontaneously
- when they break down, these radioisotopes EMIT RADIATION which is dangerous to living things
- 3 forms of radiation: gamma, alpha, beta
- radioisotopes are used for: power generation, sterilisation of surgical equipment, crime detection, preservation of food
14-C used for carbon dating
isotopes of Iodine used as tracers in medicine for treating / diagnosing illness
What is Heisenberg’s uncertainty principle?
It is impossible to know the exact position of an electron at a precise moment in time
what provides evidence for sublevels?
ionisation energy
what provides evidence for sublevels?
ionisation energy
What type of structure does Si (Silicon) have?
- metalloid
- macromolecular covalent structure
- very strong bonds
- very high melting point
define ionisation energy
energy required to remove one mole of electrons from 1 mole of gaseous atoms to produce 1 mole of gaseous 1+ ions
X (g) –> X+ (g) + e-
Why are Be –> B and Mg –> Al exceptions to trend of ionisation energy?
- B has higher NUCLEAR CHARGE than Be, but ionisation energy is lower
- electrons in p-orbital are of HIGHER ENERGY & FURTHER FROM THE NUCLEUS than electrons in s orbital, hence they require SLIGHTLY less energy to remove
Why are N –> O and P –> S exceptions to trend of ionisation energy?
- S has lower ionisation than P
- electron in same p-orbital as another electron is easier to remove than one in an orbital by itself due to REPULSION of other electron
define electron affinity
energy RELEASED when one mole of electrons is added to one mole of gaseous atoms to produce one mole of gaseous 1- ions
X (g) + e- –> X- (g)
is electron affinity exothermic or endothermic?
exothermic for FIRST electron, endothermic for SECOND electron
How can alkali metals be prevented from reacting with air?
they can be stored under liquid paraffin
How does alkali metals react w/ water?
- lithium floats & reacts quietly
- sodium melts into a ball which darts around on surface
- potassium –> heat generation, ignites hydrogen
why does melting points of ALKALI metals decrease down group 1 but increase down group 7?
- WEAKER METALLIC FORCES FOR GROUP 1
- STRONGER LDF FORCES FOR GROUP 7
Which halogens for gaseous compounds with hydrogen?
HF, HI, HCl, & HBr (everything except Astatine)
What do alkali metal halides react to form?
they are SOLUBLE & they react to form COLOURLESS, NEUTRAL SOLUTIONS
(it is the diatomic molecule that produces the colour)
group 1 are …?
good REDUCING agents
group 17 are . . .?
good OXIDIZING AGENTS
does aluminium oxide react with wateR?
NO
how can the presence of halide ions in solution be detected?
by adding silver nitrate solution - the silver ions react with the halide ions to form a precipitate of the silver halide –> silver halides can be distinguished by their color
colours of silver halides
The silver chloride compound forms a white precipitate, silver bromide a creamy coloured precipitate and silver iodide a yellow coloured precipitate.
what do metal oxides form on reacting with water?
metal hydroxides
colors of the halogens?
Cl2 = green
Br2 = reddish
I2 = brown
