Inorganic Chemistry: Paper 1

repeating pattern/trends (of physical or chemical properties)

decreases along the period

increased nuclear charge for same number of electron shells and shielding, produces greater attraction to outer electron

increases along the period

decreased atomic radius and increased nuclear charge, more energy required to remove electrons

metallic bonding

high melting point as there is a strong electrostatic attraction between delocalised electrons and positive metal ions

Al the highest because greater positive charge on ions and more free electrons, greater electrostatic attraction

macromolecular

highest melting point because must overcome strong covalent bonds, requiring lots of energy.

simple molecule

lower melting point as only held together by weak van der Waal intermolecular forces, requiring little energy

S > P > Cl because S8, P4, Cl2 and greater the Mr, the greater the surface area for van der Waals, more van der Waals, more energy to overcome

simple molecule

exist as single atoms so weak van der Waals and small Mr

increase down the group

add new shell, increasing distance to outer electron, increased shielding, reducing nuclear attraction

decreases down the group

new shells, atomic radius increases, increased shielding, reduces nuclear attraction, less energy to remove an electron

decreases down the group

metallic bonding: larger the ion within the lattice weakens the attractive force as it acts over a larger distance between positive nucleus and delocalised electrons

M(s) + 2H2O(l) → M(OH)2(aq) + H2(g)

increase in reactivity down the group

Mg very slow: forms layer of Mg(OH)2 which is sparingly soluble so stops the reaction

weak alkaline solution

Mg(s) + H2O(g) → MgO(s) + H2(g)

TiCl4 + 2Mg → 2MgCl2 + Ti

displacement reaction

1. initially add 10 drops NaOH

MgCl2, CaCl2, SrCl2 = slight white ppt

BaCl2 = colourless solution

2. add excess NaOH

MgCl2 = white ppt

CaCl2, SrCl2 = slight white ppt

BaCl2 = colourless

because Mg(OH)2 is sparingly soluble

1. initially add 10 drops H2SO4

BaCl2, SrCl2 = white ppt

MgCl2, CaCl2 = slight white ppt

2. add excess H2SO4

BaCl2, SrCl2 = white ppt

CaCl2 = slight white ppt

MgCl2 = colourless solution

increases in solubility down the group

Mg(OH)2 is sparingly soluble

milk of magnesia is used as an antacid as it neutralises stomach acid, for indigestion

slaked lime is used in agriculture to raise the pH of a field (is basic)

to remove SO2 from flue gases, prevent the release into atmosphere

CaO + 2H2O + SO2 → CaSO3 + 2H2O

CaCO3 + 2SO2 + H2O → Ca(HSO3)2 + CO2

decrease in solubility down the group

BaSO4 is insoluble

barium meal is digested and pass through digestive system, allowing the outlining of the gut by medical x-rays

it is completely insoluble so will not dissolve into blood, despite being toxic

1. acidify solution with HNO3/HCl

(to remove CO2, which if present forms a false positive)

2. add BaCl2

white precipitate if present (as BaSO4 is formed)

1. add HCl

2. collect gas formed

3. bubble through limewater (Ca(OH)2)

cloudy, white solution if present

1. add equal amount of NaOH

2. heat the sample

3. place moist, red litmus over the mouth of tube as gas give off is ammonia

will turn blue

NH4+ + OH- → NH3 + H2O

turns red litmus paper blue

either by dipping it in NaOH solution

or

place moist, red litmus paper in petri dish with ammonia solution (on filter paper) on the other side, ammonia vapour will turn paper blue

increases down the group

atomic radius increases increasing the strength of the van der Waal forces, greater Mr has greater surface for them to act on

I = solid, Br = liquid, Cl = gas

must be oxidised itself, lose its own electron

halide ions (I-) are best, most likely to lose electrons

increase down the group

atomic radius and shielding increases, reduces nuclear attraction

must be reduced itself, gain electrons

halogen (F2) molecules are best, most likely to gain electrons

decrease down the group

atomic radius and shielding increases, reduces nuclear attraction less attraction to electrons

decrease down the group

atomic radius and shielding increases, reduces nuclear attraction less attraction to electrons

Cl displaces Br = orange/red colour

Cl/Br displaces I = black precipitate

1. add HNO3

prevents false positive from carbonate ions

2. add AgNO3

Ag+(aq) + X- → AgX(s)

AgCl = white precipitate

AgBr = cream precipitate

AgI = yellow precipitate

1. add dilute ammonia

AgCl will dissolve, precipitate disappears

AgCl + NH3 → [Ag(NH3)2]+ + Cl-

2. add concentrated ammonia

AgBr will dissolve

AgI is insoluble

H2SO4(l) + NaCl(s) → HCl(g) + NaHSO4(s)

HCl = white misty fumes

H2SO4(l) + NaBr(s) → HBr(g) + NaHSO4(s)

2HBr(g) + H2SO4(l) → Br2(g) + SO2(g) + 2H2O(l)

HBr = white misty fumes

Br2 = reddish-brown gas

SO2 = choking fumes?

Br- acting as reducing agent

H2SO4(l) + NaI(s) → HI(g) + NaHSO4(s)

2HI(g) + H2SO4(l) → I2(s) + SO2(g) + 2H2O(l)

6HI(g) + H2SO4(l) → 3I2(s) + S(s) + 4H2O(l)

8HI(g) + H2SO4(l) → 4I2(s) + H2S(g) + 4H2O(l)

HI = white misty fumes

I2 = violet/purple vapour

SO2 = choking fumes?

S = yellow solid

H2S = toxic, bad smelling gas

Cl2(aq) + 2NaOH(aq) → NaCl(aq) + NaClO(aq) + H2O(l)

NaClO =household bleach that can kill bacteria, water treatment, and bleach paper and textiles

Cl2 + H2O → ClO- + Cl- + 2H+

Cl2 + H2O → HClO + HCl

disproportionation reaction

2Cl2 + 2H2O → 4HCl + O2

UV light is present

(+) kills disease-causing microorganisms

prevents algae growth

(-) chlorine is harmful, respiratory and carcinogenic

organic chlorine compounds harmful to environment

(=) however, benefits outweigh the negatives

reacts vigorously with cold water, fizzing H2 gas and forms a ball

producing strong alkaline solution

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

sodium is more reactive than magnesium as it requires less energy to remove 1 electron than 2, more energy need to form Mg2+ ions

Na2O, MgO, Al2O3, SiO2, P4O10, SO2 and SO3

2Na + 1/2O2 → Na2O(s)

Mg + 1/2O2 → MgO(s)

2Al + 1 1/2O2 → Al2O3(s)

Si + O2 → SiO2(s)

P4 + 5O2 → P4O10(s)

S + O2 → SO2(g)

giant ionic lattice

strong attractive forces between ions

MgO > Na2O (mp) Mg2+ attract the O2- more greatly

MgO > Al2O3 (mp) Al3+ distorts electron cloud of O2- and some covalent character lowers E

macromolecular

many strong covalent bonds to overcome, requiring lots of energy

simple molecular

weak intermolecular bonds, require little E to overcome

Na2O + H2O → 2NaOH

MgO + H2O → Mg(OH)2

alkaline solutions pH 12-14 and 9-10 respectively

eg. P4O10 + 6H2O → 4H3PO4(aq)

acidic solutions, pH 0-2

SiO2 = insoluble

Al2O3 = amphoteric, insoluble

will react with acid and base to form a salt

(acting as either acid/base)

eg. 2HCl + MgO → MgCl2 + H2O

react with acid to form salt

MgO and Na2O

eg. 12NaOH + P4O10 → 4Na3PO4 + 6H2O

react with base to form salt

SiO2, P4O10, SO2 and SO3

acting as acid with base

2NaOH + Al2O3 + 3H2O → 2NaAl(OH)4

sodium tetrahydroxoaluminate

acting as base with acid

Al2O3 + 3H2SO4 → Al2(SO4)3 + 3H2O

elements with incomplete d-subshell that can form at least one stable ion with an incomplete d-subshell

central metal atom/ion surrounded by ligands

molecule/ion that forms a co-ordinate bond with a transition metal by donating a pair of electrons

number of co-ordinate bonds to the central metal atom/ion

bidentate/multidentate more energetically favourable than monodentate

because entropy change is always positive as there is a net increase in the number of particles

so ΔG = negative

occurs in square planar and octahedral complexes

cis = 90°

trans = 180°

could cause change in properties due to polarity

occurs in tetrahedral and octahedral complexes

a mirror image of the 2 complexes that are not superimposable

Pt bound to 2 Cl- ions and 2 NH3 molecules, ligands 90° from the same molecule, square planar structure

binds to DNA, prevents cell division, and tumour growth

Ag+ forms linear complex

[Ag(NH3)2]+

reduced to metallic silver to distinguish aldehydes and ketones

colour arises when some wavelengths of visible light are absorbed and the remaining wavelengths are transmitted

d-electrons move from ground state to an excited state when light is absorbed

E = hf = hc/λ

E = energy of visible light (J)

h = Planck’s constant (6.63 x10-34)

f = frequency of light (Hz or s-1)

c = speed of light (3 x8 ms-1)

λ = wavelength of light (m)

type of ligand

co-ordination number

oxidation state (change in)

different ligands will split d-orbital by different energies

depends on the repulsion of each ligand

influences strength of metal ion-ligand interaction

strength of metal-ion ligand interactions varies due to nuclear charge

eg. Mn(II) = Fe(III) electron configuration

however, Fe(III) has greater nuclear charge so its change in energy is greater, absorbing visible light of greater energy.

catalyst in a different state/phase from the reactants

reactions occur at the active site on the surface

catalyst in the same state/phase as the reactants

reactions proceed through an intermediate species

2SO2 + O2 → 2SO3

catalyst = V2O5

2SO2 + 2V2O5 → 2V2O4 + 2SO3

O2 + 2V2O4 → 2V2O5

N2 + 3H2 → 2NH3

catalyst = Fe

N2 and H2 diffuse to Fe surface and adsorb to it, weakening their covalent bonds so reaction can take place

product molecule desorbs from surface

overall = S2O82- + 2I- → I2 + 2SO42-

catalyst = Fe2+ ions

1. S2O82- + 2Fe2+ → 2SO42- + 2Fe3+

2. 2I- + 2Fe3+ → I2 + 2Fe2+

Fe acts as reducing and oxidising agent

both negative ions so require catalyst as they repel and activation energy is high

overall:

2MnO4- + 5C2O42- + 16H+ → 2Mn2+ + 10CO2 + 8H2O

catalyst = Mn2+

4Mn2+ + MnO4- + 8H+ → 5Mn3+ + 4H2O

2Mn3+ + C2O42- → 2Mn2+ + 2CO2

Lewis acid = accept lone pair

Lewis base = donate lone pair

metal complex = central metal ion = acid, ligand = base

acidity of M3+ is greater than M2+

M3+ is smaller with a higher charge density than M2+, more strongly polarising

M3+ pulls the O’s electrons of H2O more greatly, weakening the O-H bond, H+ is more easily released

eg. [Fe(H2O)6]3+ ⇌ [Fe(H2O)5OH]2+ + H+

aluminium hydroxides dissolve in acids and base

in acid = [Al(H2O)6]3+

in neutral = Al(H2O)3(OH)3

in base = [Al(OH)4]-