exam Flashcards
primary standard solution
a solution containing one solute, prepared by dissolving a known mass of that solute in a known volume of water. As a result the concentration is known accurately
primary standard
a substance that can be prepared pure and dissolved in water to make a solution whose concentration is accurately known
where are the strongest oxidants on the electrochemical series
top left (at cathode)
rules for ox number
F = -1
H to non-metals is +1, H to metals is -1
Oxygen in peroxides is -1
salt bridge function
contain free-moving unreactive ions that keep polarity/charge constant
cell potential
E (cathode) - E (anode)
water properties
high latent heat
high specific heat capacity
high melting and boiling point
universal sovent
why does water expand upon freezing
as cools, molecules slow down and water adopts more regular lattice bc rigid H bonds bw molecules
this -> hexagonal lattice as ice pushes molecules further apart vs liquid form, expanding liquid water
tf same no of molecules occupy larger space and ice has a lower density
latent heat of fusion
nrg required to convert 1 mol of substance from s to l at its melting point
latent heat of vaporisation
nrg required to convert 1 mol of substance from l to g as it’s boiling point
specific heat capacity
amount of nrg required to raise the temp of 1g of substance by 1 degree C
Q=mcAT
process of dissolving
forces being formed need to be approximately the same strength or stronger than forces being broken
“bonds being formed are weaker than those that were broken tf immiscible”
insoluble ions
halides w Ag, Pb, Hg
SO4 w Pb or Ba
O, S, CO3, PO4 except for G1
OH except G1, Ba or Ca
ppm
mg/L or ug/g
w/w%
w/v%
v/v%
g/g
g/mL
mL/mL
crystallisation
solid crystals form as temp decreases and the solute can no longer remain dissolved. the slower the cooling, the bigger the crystals
Kw - ionic product of water
[OH][H3O] = 10 ^-14
ph
-log [H]; 14 + log[OH]
10 ^-pH; 10 ^pH-14
assumption with diprotic acids
assume all molecules eg H2SO4 dissociate and all hydrogen ions contribute to pH
Ka (weak acids)
[H+]^2 / [acid]
collision theory
for a chemical reaction to occur, reactant particles need to collide with sufficient nrg and the correct orientation
factors affecting the rate of reaction
increase fq of successful collision:
SA of solid
concentration of solution
pressure (by decreasing volume)(Boyle’s law)
increase proportion w nrg > = Ea
temperature
catalysts (reduce Ea)
dynamic equilibrium
rate of forward reaction = rate of reverse reaction
Le Chatelier’s Principle
system at equilibrium has a tendency to partially oppose a change
orbital
region of space in which up to 2 e are likely to be located. Orbitals may also be empty
Pauli’s Exclusive Principal
a max of 2 e in a given orbital of opposite spins
Hund’s Rule of Maximum Multiplicity
every orbital in a sub shell is half-filled before any orbital in that subshell is filled
Aufbai=u Principal
subshells are filled in order from lowest to highest nrg
electron configuration exceptions
Chromium and Copper
cc
measure of net attractive force felt by valence e towards the nucleus
protons- inner shell e
electronegativity
strength with which atoms of an element attract electrons when they are chemically combined with another element
ionisation nrg
amount of nrg required to remove an electron from 1 mol of a gaseous atom
mettalic bonding
electrostatic force of attraction in lattice between sea of delocalised e and positively charged cations
covalent bonding
shared pair of e bw two non-metal ions
dative covalent bond
both of shared electrons are contributed by one atom only
fuel
substance that burns in air or oxygen to release a usable amount of nrg
substitution reaction (alkanes)
UV light
haloalkane + OH –>
alcohols
alkene + hydrogen
Ni catalyst + 150C
alkene + water
(steam) H3PO4, 300C, 60-70atm
thermoplastic
no cross-links
chains loosely tangled together
low mp
can be remoulded
eg plastic bags/cling wrap
thermosetting
cross-link bw chains
rigid and inflexible
X be remoulded
eg kitchen bench cover
elastomers
can be stretched/deformed
retain their shape
few cross-links
polymerisation
under pressure w catalyst
LDPE
Low density polyethene:
high temp and pressure
amorphous (branched chains that don’t fit well)
low mp
soft and flexible
eg carrier bags, plastic wrap
HDPE
high density polyethene:
cataylst at lower temp
unbranched chains that fit together
more cyrstalline and less amorphous
eg wheelie bins. classroom chairs
