mod 2 foundations Flashcards
isotopes
same number of protons & electrons different number of neutrons
Relative atomic mass
the weighted mean mass of an element relative to 1/12 of an atom of carbon-12
Relative isotopic mass
The mass of an atom of isotope compared with 1/12 of the mass of an atom of carbon-12
Calculate RAM
(% x mass) + (% x mass)
100
Moles
The amount of substance that contains 6.02 x 10^23 of particles same as 12g of carbon-12
avogadros constant
6.022 x 10^23
N= n x NA
Ideal gas law
PV = nRT P=pressure (pa) V=volume(m3) R=constant(8.31) T=temp (k)
properties of ideal gas law
- all particles are identical & in random continuous motion
- particles travel in straight lines
- the particles dont react when they collide
- the particles have no intermolecular forces between them
Molar gas volume
At room temp and pressure, 1 mole of gas occupies a volume of 24dm3
V= n x 24dm3
Percentage yield
actual yield / theoretical yield
x100
Atom economy
Mr of desired product / sum of all Mr of reactants
Water of crystalisation
Water molecules that form part of the crystalline structure
anhydrous-dehydrated (no water)
hydrated(water)
metallic bonding
strong electrostatic force of attraction between positively charged ions and sea of delocalised electrons
- high melting and boiling points
- good conductors (solid&liquid)
- malleable&ductile
covalent bonding
strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atom
eg-N2,CO2
Dative covalent bond
one element gives both electrons to the bond
eg-NH4
Ionic bonding
electrostatic attraction between positive & negative ions
-metal&non metal
-giant lattices
higher the charge the stronger the bond
general equations
Acid + metal = salt + hydrogen
Acid + base =salt +water
Acid + metal carbonate= salt+ water+ carbon dioxide
Oxidation state
tells us the charge of an element, indication of how many electrons an element has lost or gained
oxidation state rules
-all elements in their uncombined state has an oxidation state of 0
-oxygen normally -2
cl is different if binded with fluorine or oxygen
-hydrogen have +1 unless bonded to metal -1
bases
substances that can react with an acid to forma salt
- sodium hydroxide (NaOH)
- potassium hydroxide(KOH)
- ammonia- (NH3)
electron shells
2,8,18,32
s=2, p=6, d=10 f=14
1s,2s,2p,3s,3p,4s,3d etc
orbitals
s-orbitals sphere shape p orbitals -dumbell shape (3 kinds) each orbital hold 2 electrons so therefore in p shell there are 3 orbital shells
short hand notation
write the nearest noble gas in square brackets then write the continuing shells
electron configuration
-draw with single headed arrows
opposite way to eachother as electrons repel
-put electrons in each box before filling each pair out
most stable if half full or full
shapes of molecules
linear = 180 (co2) triganal planar = 120 (BCl3) tetrahedral = 109.5 (CH4) pyramidal = 107 (NH3) non-linear = 104.5 (H2O) octahedral = 90 (SF6) -lone pairs repel more than bonded
electronegativity
-an atoms ability to attract bonding electrons in a bond
-measured using pauling scale
-Across periodic table; electronegativity increases,nuclear charge increases, ar decreases
less than 0.5 = non polar
0.5 - 1.8 = polar
bigger than 1.8 = ionic
Bond polarity
non polar- if elements are similar in electronegativity or the same eg H2
polar- if electronegativities are different eg HCl
separation of opposite charges (dipoles)
Solvents dissolve in like substances
polar dissolves in polar
intermolecular forces
induced dipole (london forces) - weak forces that exist between all molecules; electrons move to one side causing a temporary charge permanent dipole - stronger than london; exist in polar covalent bonds hydrogen - strongest force; dipole bonds with lone pair, between H-N,F,O
Anomolous water properties
ice is less dense than water - hydrogen bonds hold water molecules apart in a lattice
- water has relatively high boiling point
- high surface tension
empirical formula
simplist whole number ratio
-work out number of moles of each then divide by smallest number of moles
will give you a ratio then round to nearest whole number
uncertainty
% = (2x) uncertainty / quantity measured
x100
-(2x) if using a burette as there are 2 uncertainties
compound charges
sulphate - SO4 (2-) nitrate - NO3 (-) carbonate CO3 (2-) hydroxide OH (-) ammonium NH4 (+)
