a level inorganic

USE THIS FOR NOTES !!! i cba to update other fcs from before combining

finish the eqn: acid + base →

acid + base → salt + water

give and explain the eqn for the reaction between sodium oxide and hydrochloric acid:

• Na₂O + 2HCl → 2NaCl + H₂O

• Na₂O is basic - neutralises HCl (acid)

give and explain the eqn for the reaction between magnesium oxide and sulfuric acid:

• MgO + H₂SO₄ → MgSO₄ + H₂O

• MgO is basic - neutralises H₂SO₄ (acid)

give and explain the eqn for the reaction between silicon dioxide and sodium hydroxide:

• SiO₂ + 2NaOH → Na₂SiO₃ + H₂O

• SiO₂ is acidic so neutralises NaOH (base)

give and explain the eqn for the reaction between phosphorous oxide and sodium hydroxide:

• P₄O₁₀ + 12NaOH → 4Na₃PO₄ + 6H₂O

• P₄O₁₀ is acidic so neutralises NaOH (base)

give and explain the eqn for the reaction between sulfur dioxide and sodium hydroxide:

• SO₂ + 2NaOH → Na₂SO₃ + H₂O

• SO₂ is acidic so neutralises NaOH (base)

give and explain the eqn for the reaction between sulfur trioxide and sodium hydroxide:

• SO₃ + 2NaOH → Na₂SO₄ + H₂O

• SO₃ is acidic so neutralises NaOH (base)

give and explain the eqn for the reaction between aluminium oxide and sulfuric acid:

• Al₂O₃ + 3H₂SO₄ → Al₂(SO₄)₃ + 3H₂O

• Al₂O₃ is amphoteric but in this case neutralises H₂SO₄ (acid)

give and explain the eqn for the reaction between aluminium oxide and sodium hydroxide:

• Al₂O₃ + 2NaOH + 3H₂O → 2NaAl(OH)₄

• Al₂O₃ is amphoteric but in this case neutralises NaOH (base)

how does Na react with water?

• floats on and moves about surface of water

• fizzes and melts to form a silvery ball

• eventually disappears and solution remaining is colourless

give the eqn for the reaction of Na with water:

2Na _(s) + 2H₂O _(l) → 2NaOH _(aq) + H_{2 (g)}

how does Mg react with water?

• reacts v slowly w/ water

• will produce a small vol of hydrogen when left in contact w/ water for several weeks :(

give the eqn for Mg reacting with water:

Mg _(s) + 2H₂O _(l) → Mg(OH)_{2 (aq)} + H_{2 (g)}

how does Mg react with water vapour? give the observation:

• reacts vigorously with water vapour at temps > 100 ^oC (373K) in absence of air

• forms a white powder and bright/white light

give the eqn for Mg’s reaction with water vapour:

Mg _(s) + H₂O _(g) → MgO _(s) + H_{2 (g)}

give the observation and the eqn for the reaction of sodium with oxygen:

• yellow flame observed, white solid formed

• 4Na + O₂ → 2Na₂O

give the observation and the eqn for the reaction of magnesium with oxygen:

• burns in air - white light observed and white powder/solid formed

• 2Mg + O₂ → 2MgO

state and explain the difference in how aluminium powder and foil react with oxygen/water:

• aluminium powder reacts readily

• but aluminium foil does not react as easily - has protective oxide layer which prevents reaction with oxygen and water, ∴ preventing corrosion

give the eqn for the reaction of aluminium with oxygen:

4Al + 3O₂ → 2Al₂O₃

give the explanation and eqn for the reaction of silicon with oxygen:

• finely /ed silicon reacts with oxygen when heated, forming silicon dioxide

• Si + O₂ → SiO₂

give the observation and eqn for phosphorous reacting in limited oxygen:

• phosphorous burns vigorously with a white flame

• P₄ + 3O₂ → P₄O₆

give the observation and eqn for phosphorous reacting in XS oxygen:

• phosphorous burns vigorously with a white flame

• P₄ + 5O₂ → P₄O₁₀

give the observation and eqn for sulfur’s initial reaction with oxygen:

• burns in air - yellow solid sulfur melts to form a red liquid

• this then burns with a blue flame, forming misty fumes of a choking, pungent gas

• S + O₂ → SO₂

give the eqn for sulfur’s further reaction with oxygen and state the conditions:

• 2SO₂ + O₂ → 2SO₃

• more oxygen, vanadium (V) oxide catalyst, specific temp/pressure conditions

how do halogens react w/ oxygen?

form unstable oxides

do noble gases react with oxygen?

no - inert

describe and explain the overall trends in the mpts of the period 3 oxides from Na₂O → Al₂O₃:

• increase, decrease (respectively)

• overall: high mpts as form giant ionic lattices - strong electrostatic forces of attraction require a large amount of E to overcome

how and why does the mpt change from Na₂O to MgO?

• increase

• Mg is smaller and has a bigger charge and so a greater charge density

how and why does the mpt change from MgO to Al₂O₃?

• decrease

• smaller electronegativity diff between Al and O than Mg and O

• so oxygen ions in Al₂O₃ don’t attract e^- in the metal-oxygen bond as strongly as in MgO

• so Al₂O₃ bonds are partially covalent

how and why does the mpt change when you reach SiO₂?

• decrease - but still higher compared to other non metal oxides

• as has a giant covalent structure with strong covalent bonds which require a large amount of energy to break

describe and explain the overall trend in the mpts of the period 3 oxides from P₄O₁₀ → SO₂:

• decrease, decrease (respectively)

• low mpts as are simple molecular structures - weak IMF: DPDP and VDWs which require little energy to overcome

how do Na₂O and MgO react with water? refer to the ions and state the ionic eqn:

• dissolve in water

• O^2- ions react with water to form OH^-, forming alkaline solutions

• O^2- + H₂O → 2OH^-

give the eqn for Na₂O reacting with water:

Na₂O _(s) + H₂O _(l) → 2NaOH _(aq)

give the eqn for MgO reacting with water and state the additional observation:

MgO _(s) + H₂O _(l) → Mg(OH)_{2 (aq)} - bright white flame

are Na₂O and MgO acidic, amphoteric or basic oxides? why?

basic - react with acids (to form bases)

which 2 group 3 oxides are insoluble in water and why?

• Al₂O₃ and SiO₂

• dessicants - absorb water into structure

is SiO₂ basic, acidic, or amphoteric? what does this mean?

acidic - reacts with bases (to form acids)

are sulfur oxides acidic, basic or amphoteric? what does this mean?

acidic - react with bases (to form acids)

give the eqn for the reaction of phosphorous oxide with water:

P₄O_{10 (s)} + 6H₂O _(l) → 4H₃PO_{4 (aq)}

give the eqn for the reaction of sulphur dioxide with water and name the product:

SO_{2 (g)} + H₂O _(l) → H₂SO_{3 (aq)} - sulphurous acid

give the eqn for the reaction of sulfur trioxide with water and name the product:

SO_{3 (g)} + H₂O _(l) → H₂SO_{4 (aq)} - sulphuric acid

is silicon dioxide soluble in water? is it acidic, basic or amphoteric?

• insoluble

• acidic - reacts with bases (to form acids)

is aluminium oxide water soluble? is it acidic, basic or amphoteric?

• insoluble

• amphoteric - reacts with both acids and bases

give the formula and structure of the phosphate (V) ion:

give the formula and structure of the sulfite (IV) ion:

give the formula and structure of the sulfate (VI) ion:

give the formula and structure of sulfuric acid:

H₂SO₄

give the formula and structure of sulfuruous acid:

H₂SO₃

give the formula and structure of phosphoric acid:

H₃PO₄

give the formula of a hydroxide of an element in period 3 used in medicine:

Mg(OH)₂

why are transition metals good catalysts?

• have variable oxidation states

• so are able to form a range of compounds by gaining/losing e^- w/in their d orbitals

in which process does vanadium act as a catalyst? give the eqns for this process:

Contact Process - industrial process for making H₂SO_{4 :}

• S + O₂ → SO₂

• SO₂ + ½ O₂ → (V₂O₅ catalyst) SO₃

• SO₃ + H₂O → H₂SO₄

give and explain pair of eqns for the use of V₂O₅ as a catalyst in the Contact Process:

V₂O₅ oxidises SO₂ to SO₃ and is itself reduced to V₂O₄:

• V₂O₅ + SO₂ → V₂O₄ + SO₃

the reduced catalyst is then oxidised back to its original state:

• V₂O₄ + ½ O₂ → V₂O₅

what is a heterogeneous catalyst?

catalyst which exists in a different phase from the reactants

explain how a heterogenous catalyst works:

• reactants adsorb onto active sites on the surface of the heterogenous catalyst

• bonds weaken/reaction takes place

• products desorb from surface

give 2 egs of heterogenous catalysts and their eqns:

Fe in the Haber process:

• N_{2 (g)} + 3H_{2 (g)} → (Fe _(s) catalyst) 2NH_{3 (g)}

V₂O₅ in the Contact process:

• SO_{2 (g)} + ½ O_{2 (g)} → (V₂O_{5 (s)} catalyst) SO_{3 (g)}

how can we minimise the cost of a reaction using a heterogenous catalyst?

• maximise SA so increase no. of molecules that can react at the same time

• this can be achieved by using powder/small pellets/support medium

give and explain an example of a support medium and provide the eqn:

• catalytic converters contain a ceramic lattice coating in a thin layer of Rh/Pt/Pd

• 2CO _(g) + 2NO _(g) → (Rh _(s) catalyst) 2CO_{2 (g)} + N_{2 (g)}

what is catalyst poisoning? what effects does this have?

• catalysts can be poisoned when impurities adsorb onto the active sites of the catalyst, blocking them

• this decreases the efficiency of catalysis, increasing costs

give 2 examples of catalyst poisoning:

• lead can coat the inner surface of a catalytic converter

• sulfur can poison the active sites on the iron catalyst in the Haber process, forming iron sulfide (sulfur found in fossil fuels used to produce H₂)

what is a homogeneous catalyst?

catalyst which exists in the same phase as the reactants (typically liquids/solutions)

how do homogeneous catalysts work?

• work by forming an intermediate species which then reacts to form the products

• the E_a needed to form the intermediate species is lower than that needed to make the products directly

give an example of a homogeneous catalyst and give the eqn for the reaction it catalyses:

Fe²⁺ ions catalyse the reaction between peronodisulfate ions and iodide ions:

• S₂O₈^2- _(aq) + 2I^-_(aq) → (Fe²⁺ _(aq) catalyst) I_{2 (aq)} + 2SO₄^2- _(aq)

why is the reaction between peronodisulfate ions and iodide ions slow without a catalyst?

-ve charges repel so high E_a

give a pair of eqns to show how Fe²⁺ acts as a catalyst in the reaction between peronodisulfate ions and iodide ions:

S₂O₈^2- _(aq)  + 2Fe²⁺ _(aq) → 2Fe³⁺ _(aq) + 2SO₄^2- _(aq)

2Fe³⁺ _(aq) + 2I^- _(aq) → I_{2 (aq)} + 2Fe²⁺ _(aq)

other than having variable oxidation states, explain why Fe²⁺ ions are good catalysts for the reaction between peronodisulfate ions and iodide ions:

+ve ions attract -ve ions in catalysed process

give an example of a homogeneous catalyst which undergoes autocatalysis and give the overall eqn for the reaction it catalyses:

Mn²⁺ ions autocatalyse the reaction between C₂O₄^2- and MnO₄^- :

• Mn²⁺ is a product of the reaction and acts as a catalyst

• ∴ as the reaction progresses, amount of product increases

• 2MnO₄^- _(aq) + 16H⁺ _(aq) + 5C₂O₄^2- _(aq) → 2Mn²⁺ _(aq) + 8H₂O _(l) + 10CO_{2 (g)}

give a pair of ionic eqns to show how Mn²⁺ ions act as a catalyst in the reaction between C₂O₄^2- and MnO₄^- :

• 4Mn²⁺ _(aq) + MnO₄^- _(aq) + 8H⁺ _(aq) → 5Mn³⁺ _(aq) + 4H₂O _(l) (Mn²⁺ oxidised back to Mn³⁺ by MnO₄^-)

• 2Mn³⁺ _(aq) + C₂O₄^2- _(aq) → 2Mn²⁺ _(aq) + 2CO₂ (g) (Mn³⁺ reduced to Mn²⁺ by C₂O₄^2-)

the reaction between C₂O₄^2- and MnO₄^- is very slow at first - explain why the reaction is initially slow (3)

• no catalyst at start

• 2 -vely charged ions repel

• E_a for reaction high

why does Mn²⁺ lower the E_a of the reaction between C₂O₄^2- and MnO₄^- ?

E_a lowered because oppositely charged ions attract

give and explain the shape of a conc-time graph of MnO₄^-:

• initially gradient shallow as RoR low as reaction is uncatalysed as too few Mn²⁺ ions made ∴ high E_a

• RoR increases w/ time as more of autocatalyst is made

• graph begins to level off as MnO₄^- used up

give and explain the shape of a conc-time graph of S₂O₈^2- in the reaction between S₂O₈^2- and I^-:

• reaction slow because 2 -ve ions repel

• Fe²⁺ attracts S₂O₈^2- so lowers E_a

• Fe²⁺ oxidised to Fe³⁺

a student determines the conc of ethanedioate ions in an acidified soln by titration w/ potassium managanate (VII) soln.

2MnO₄^- + 5C₂O₄^2- + 16H⁺ → 2Mn²⁺ + 10CO₂ + 8H₂O

the mixture is warmed before the addition of potassium manganate (VII) soln because the reaction is slow at first, when more potassium manganate (VII) is added, the mixture goes colourless quickly due to the presence of an autocatalyst.

explain the meaning of the term autocatalyst and explain, using eqns where appropriate, why the reaction is slow at first and then goes quickly (6)

• autocatalyst - product of reaction catalyses the reaction

• slow: -ve ions repel

• high E_a

• attraction between oppositiely charged ions

• 4Mn²⁺ + MnO₄^- + 8H⁺ → 5Mn³⁺ + 4H₂O

• 2Mn³⁺ + C₂O₄^2- → 2Mn²⁺ + 2CO₂

explain why complexes formed from TM ions are coloured (3)

• d orbitals have different e/d orbital Es are split

• e^- absorb some wavelengths of visible light

• to excite e^- in d orbitals

• remaining/complementary wavelengths of light reflected to give colour seen

state the origin of the colour of TM complexes (1)

• e^- excited in d shell

• E in visible range

give the eqn for calculating the difference in E and state what each symbol corresponds to:

ΔE = h ν = hc / λ, where:

• ΔE: energy absorbed / J

• h: Planck’s constant (6.63 × 10^-34 J)

• v (Greek letter nu): freq of light absorbed / Hz

• c: speed of light = (2.998 × 10⁸ ms^-1)

• λ: wavelength of light absorbed / m

give 3 factors which might affect the colour of a transition metal complex:

• change in oxidation state

• change in coordination number

• change in ligand

how can we use colorimetry to determine the concentration of transition metal ions in a solution of unknown concentration?

1. add an appropriate ligand to intensity colour

2. make up solutions of some known concentrations and measure absorbance

3. plot calibration curve of of absorbance v conc

4. measure absorbance of coloured complex and find conc from graph

what is a transition metal?

a metal that can form one or more stable ions w/ an incomplete d sub level

by definition, which 2 elements in the d block of the periodic table are not transition metals?

• Sc

• Zn

when figuring out e^- configurations of the transition metals, in which order do we fill the orbitals? what does this mean for the ionisation of transition metals?

• 4s before 3d

• so when transition metals become ions, they lose 4s e^- before 3d e^-

give and explain the two exceptions to the electron configuration rule:

• Cr - [Ar] 4s¹ 3d⁵

• Cu - [Ar] 4s¹ 3d¹⁰

• as a half or fully filled subshell is more stable than a partially filled one

give 2 physical properties of transition metals:

• high densities

• high mpts/bpts

what is a physical property?

a characteristic of a substance that can be observed or measured without changing its chemical composition

give 4 chemical properties of transition metals:

• form coloured ions

• very good catalysts

• have variable oxidation states

• form complex ions

what is a chemical property?

properties which can only be observed or measured during a chemical reaction

give a transition metal with a variable oxidation state and explain why it has this:

Fe²⁺ and Fe³⁺ as the 4s and 3d orbitals are very similar in energy so different nos. of e^- can be lost/gained

suggest why the oxidation stat eof chromium is zero in Cr(PF₃)₆ (1)

PF₃ is neutral and whole complex is neutral

what is an enantiomer?

isomers which are non-superimposable mirror images of each other

what is a chiral carbon?

C atom with 4 different attached groups

how does optical isomerism exist in transition metal complexes?

• exists in octahedral complexes when the ion has 3 bidentate ligands bonded to it

• these can ∴ form a pair of enantiomers

give an example of a transition metal complex displaying optical isomerism:

[Cu(en)₃]²⁺

what is cis-trans isomerism?

form of steroisomerism where identical groups can be positioned either adjacent (cis) or opposite (trans) each other

where can cis-trans isomerism be seen in transition metal complexes?

• square planar complexes that have 2 pairs of ligands

• octahedral complexes - 2 of one ligand, 4 of another 

give a complex that displays cis-trans isomerism and name the two isomers:

PtCl₂(NH₃)₂:

• cis isomer = cisplatin

• trans isomer = transplatin 

how do we distinguish between cis and trans isomers in octahedral complexes?

• if the 2 ligands which are the same are opposite each other and so have an angle of 180^o between them = trans

• if the 2 ligands which are the same next to each other and so have an angle of 90^o between them = cis

what are redox titrations used for?

to find the concentration of an oxidising/reducing agent in solution (i.e. how much oxidising agent is needed to exactly react with a quantity of reducing agent)

why do you not need an additional indicator for a redox titration? give an example:

• redox titrations are self indicating

• purple potassium manganate (VII) is reduced to pale pink manganese (II) ions

give the ½ eqn for the reduction of potassium manganate (VII) → manganese (II) ions:

MnO₄^- + 8H⁺ + 5e^- → Mn²⁺ + 4H₂O

give the method for a typical redox titration:

1. measure out the quantity of reducing agent using a pipette (either Fe²⁺ or C₂O₄^2- ions)

2. add dilute sulfuric acid so it is in excess

3. add the oxidising agent to the burette (usually potassium manganate)

4. add the oxidising agent from the burette until the solution just changes colour (to the colour of the oxidising agent)

5. repeat to get concordant results

6. calculate the concentration of the reducing agent