Module 2 Flashcards
What are isotopes?
atoms of the same element with different numbers of neutrons and different masses
What is relative isotopic mass?
the mass of an atom of an isotope compared to 1/12th of the mass of an atom of carbon-12
What is relative atomic mass?
the weighted mean mass of an atom of an element compared to 1/12th of the mass of an atom of carbon-12
What is the mass number?
the number of protons and neutrons in the nucleus; always the biggest number
What is the atomic number?
the number of protons
What are ions?
atoms that have lost or gained electrons
How do you calculate relative atomic mass?
(abundance A x m/z A) + (abundance B x m/z B) / total abundance OR 100 (if % abundance given)
What are some complex ions?
OH⁻ (hydroxide)
NO₃⁻ (nitrate)
NH₄⁺ (ammonium)
SO₄²- (sulphate)
CO₃²- (carbonate)
Ag+ (silver)
Zn²⁺ (zinc)
What are spectator ions?
ions which aren’t involved in the reaction; they are cancelled out in simplest ionic equations
How to work out moles in solids?
n = mass / Mr
mass in grams
How to work out moles in liquids?
n = v x c
volume in dm3
concentration in moldm-3
How do you convert from cm3 to dm3 to m3?
cm3 to dm3: divide by 1000
dm3 to m3: divide by 1000
cm3 to m3: divide by 1000000
How to work out moles in gases?
n = v / 24dm3
What is the ideal gas equation?
pV = nRT
pressure in Pa
volume in m3
R (gas constant) is 8.31 JK-1mol-1
temperature in K
What are the standard conditions?
`298K
100kPa
What is the empirical formula?
the simplest whole number ratio of elements in a compound
How to work out percentage yield?
(actual yield / theoretical yield) x 100
How to work out atom economy?
(Mr of desired product / Mr of all products) x 100
balance equation and use big numbers when calculating moles
What are acids?
proton donors; donate H+ ions which are just protons
What are bases?
proton acceptors
What is an alkali?
a soluble base; produce OH- ions
What is a weak acid?
acids which partially dissociate in solution
What is a strong acid?
acids which fully dissociate in solution
What are polyprotic acids?
acids which can donate more than 1 proton
e.g. H2SO4 (diprotic) and H3PO4 (triprotic)
What is the overall ionic equation for neutralisation?
H+ (aq) + OH- (aq) ⇌ H2O (l)
What is produced when a metal and acid react together?
a salt and hydrogen
What is produced when a metal oxide and acid react together?
a salt and water
What is produced when a metal hydroxide and acid react together?
a salt and water
What is produced when a metal carbonate and acid react together?
a salt, water and carbon dioxide
What are concordant results?
results within 0.10 cm3 of each other
How do you work out a titre?
titre = final volume - initial volume
What colours does the indicator phenolphthalein produce in acids and alkalis?
acids = colourless
alkalis = pink
What colours does the indicator methyl orange produce in acids and alkalis?
acids = red
alkalis = yellow
What is oxidation?
loss of electrons
What is reduction?
gain of electrons
What is a redox reaction?
reactions which involve both reduction and oxidation
What happens to reducing agents?
they lose electrons and so are oxidised themselves
What happens to oxidising agents?
they gain electrons and so are reduced themselves
What are the oxidation state rules?
- uncombined elements are always 0
- ions have the same charge as on the ion
- group 1 is always +1
- group 2 is always +2
- aluminium is always +3
- hydrogen is +1 except in hydrides where it is -1
- chlorine is -1 except in compounds with F or O where it is +1
- fluorine is always -1
- oxygen is -2 except in peroxides where it is -1 and OF2 where it is +2
What are the 4 subshells?
s-subshell
p-subshell
d-subshell
f-subshell
How many orbitals and therefore how many electrons can each subshell hold?
s-subshell: 1 orbital; holds 2 electrons
p-subshell: 3 orbitals; holds 6 electrons
d-subshell: 5 orbitals; holds 10 electrons
f-subshell: 7 orbitals; holds 14 electrons
How many electrons can be held in shell 1?
2 electrons (1s)
How many electrons can be held in shell 2?
8 electrons (2s, 2p)
How many electrons can be held in shell 3?
18 electrons (3s, 3p, 3d)
How many electrons can be held in shell 4?
32 electrons (4s, 4p, 4d, 4f)
What shape is the s-orbital?
spherical; the 2 electrons can move anywhere within the sphere
What shape is the p-subshell?
3 orbitals in a dumbbell shape; each orbital holds 2 electrons that can move anywhere within the shape
What is spin pairing?
when 2 electrons occupy 1 orbital and they spin in opposite directions
What are the rules to electron configuration?
- fill 4s before 3d
- place electrons singularly first then pair up (due to electron repulsion)
What are the 2 electron configuration anomalies?
- copper: fully fills 3d before 4s
- chromium: singularly fills 3d before 4s
What is ionic bonding?
the electrostatic attraction between positive and negative ions
What structure do ionic compounds have?
giant ionic lattice structure
Do ionic compounds conduct electricity?
yes when molten or aqueous; the ions dissociate and so are free to move and carry a charge
Do ionic compounds dissolve in water?
yes; most do as water molecules are polar and so they attract the positive and negative ions
Do ionic compounds have high or low melting points?
high; there are many electrostatic forces between the oppositely charged ions so a lot of energy is required to overcome them
What is covalent bonding?
electrostatic attraction between a shared pair of electrons and the positive nuclei of the bonded atoms
What is a dative covalent/coordinate bond?
where 1 atom donates both electrons in a shared pair of electrons
What are the rules to the shape of molecules?
- bond pairs repel equally
- lone pairs repel more than bond pairs
- 2 lone pairs repel even further
What is the name and bond angle of molecules with 2 bond pairs?
linear; 180°
e.g. BeCl2
What is the name and bond angle of molecules with 3 bond pairs?
trigonal planar; 120°
e.g. BF3
What is the name and bond angle of molecules with 4 bond pairs?
tetrahedral; 109.5°
e.g. CH4
What is the name and bond angle of molecules with 5 bond pairs?
trigonal bipyramidal; 90° and 120°
e.g. PCl5
What is the name and bond angle of molecules with 6 bond pairs?
octahedral; 90°
e.g. SF6
What is the name and bond angle of molecules with 3 bond pairs and 1 lone pair?
trigonal pyramidal; 107°
e.g. NH3
What is the name and bond angle of molecules with 2 bond pairs and 2 lone pairs?
non-linear; 104.5°
e.g. H2O
What is electronegativity?
the ability of an atom to attract electrons in a bonding pair to itself
What is the most electronegative element?
fluorine; the closer to fluorine the more electronegative an element is
What are induced dipole dipole forces also known as?
London forces
What are induced dipole dipole forces?
when electrons in a molecule/atom form a dipole when they move near to another atom/molecule
the δ+ on 1 atom/molecule becomes attracted to a δ- on another atom/molecule creating a force of attraction; exist in all molecules/atoms regardless of polarity but only exist when 2 molecules/atoms are nearby
What are permanent dipole dipole forces?
when the δ+ of one molecule is attracted to the δ- on another molecule; only exists in molecules with a polarity and these interactions are permanent
What is hydrogen bonding?
occurs when hydrogen on 1 molecule forms a bond with the lone pair on nitrogen, oxygen or fluorine on another molecule
Name the three intermolecular forces in increasing strength.
induced dipole dipole, permanent dipole dipole, hydrogen bonding
