topic 4 - inorganic chemistry and the periodic table Flashcards
state the trend in ionisation energy down group 2
decreases
explain the trend in ionisation energy down group 2
-decreases
-as you go down the group a quantum shell is added each time, so the electrostatic attraction between the nucleus and outermost electron decreases, so the energy of the outermost electron decreases
-shielding increases due to increased repulsion between electrons in the inner shellls, so energy of outermost electron decreases
-despite an increase in nuclear charge
what is another name for group 2 elements
the alkaline earth metals
Explain the trend in reactivity down group 2
reactivity increases down the group
Group 2 elements lose 2 electrons to form ions with a +2 charge
Ionisation energy decreases as you go down the group, so less energy is required to move the 2 outermost electrons
So reactivity increases down the group
Explain the trend in melting and boiling point down group 2
decreases down the group
Group 2 elements have metallic bonding
Down the group ionic radius increases but the number of delocalised electrons per ion stays the same
The distance between the delocalised electrons and the nucleus increases, so the electrostatic attraction decreases, so less energy is required to break the metallic bonds
describe the colour and structure of group 2 oxides
white solids
ionic lattice
How is a group 2 metal chloride formed
heat the group 2 metal with chlorine
which group 2 element doesn’t react with water
beryllium
what is the equation for the reaction between magnesium and water
Mg + H2O = MgO + H2
magnesium doesn’t fully react with water because when magnesium is exposed to water a layer of insoluble magnesium hydroxide forms around the solid prevent further reaction
magnesium oxide is a solid
what is the equation for the reaction between calcium and water
Ca + 2H2O = Ca(OH)2 + H2
state the observation when a group 2 metal oxide reacts with water
the solid dissolves to form a colourless solution
which group 2 metal oxide doesn’t react with water to form a metal hydroxide
BeO
berylium oxide
what is the equation between calcium oxide and water
CaO + H20 = Ca(OH)2
Ca(OH)2 is limewater
is the product formed from the reaction between group 2 metal oxides and water acidic, alkaline or base
metal hydroxide is formed which is a base
state the trend in solubility of hydroxides
increase in solubility down the group
DISH
increase hydroxides
state the trend in solubility of sulphates
decrease in solubility down the group
DISH
decrease sulphates
what is the test for CO2
explain the colour change
bubble CO2 through limewater Ca(OH)2
the aqueous solution of limewater will turn cloudy
because calcium carbonate is formed which is a white precipitate insoluble in water
CO2 + Ca(OH)2 = CaCO3 + H2O
what observation may be made during the neutralisation of group 2 metal oxide/hydroxide with acids
white solid dissolves to form a colourless solution
the reaction is exothermic so surroundings will increase in thermal energy
metal oxide + acid
metal hydroxide + acid
which is a neutralisation reaction
both
are group 2 metal nitrates, chlorides and sulphates soluble or insoluble
group 2 metal nitrates and chlorides are always soluble
the solubility of group 2 metal sulphates decreases down the group
describe the solubility of group 2 metal sulphates
-decreases down the group
-magnesium sulfate is soluble
-calcium sulfate is slightly soluble
-strontium sulfate and barium sulfate are insoluble
state the test for the presence of sulfate ions in a solution of sodium sulfate
what would the equation be
-add dilute nitric acid and barium nitrate solution
-a white precipitate forms of barium sulfate which is insoluble
Ba(NO3)2 aq + Na2SO4 aq = BaSO4 s + 2NaNO3 aq
explain the test for the presence of sulfate ions
-a solution with barium ions is used (e.g. barium nitrate) because barium will react with sulfate ions to form barium sulfate which is insoluble
-so a white precipitate will be seen
-there must be H+ ions present in the solution to prevent barium ions from reacting with a different anion other than sulfate ion
-so nitric acid is used
what is thermal stability
the measure of the extent to which a compound decomposes when heated
-a very thermally stable compound doesn’t decompose when heated
-a compound that is not thermally stable decomposes when heated
state what happens when a group 2 nitrate or carbonate is heated
-themal decomposition
when group 1 and 2 nitrates are heated in test tubes over a bunsen flame, what observation can be made
-nitrogen dioxide is a brown gas
-when group 1 nitrates (except lithium) are decomposed, metal nitrite and oxygen is produced
-so there will be no brown fumes
-when group 2 nitrates (and lithium) are decomposed, metal oxide, oxygen and nitrogen dioxide are produced
-so there will be brown fumes
explain what happens when group 1 nitrates are heated by a bunsen flame
E.g. sodium nitrate
-group 1 nitrates (except lithium) undergo decomposition
-the nitrite ion is produced because it is smaller, so thermal stability is achieved
-O2 gas is produced
2NaNO3 s = 2NaNO2 s + O2 g
what is the equation for the thermal decomposition of lithium nitrate
4LiNO3 s = 2Li2O s + 4NO2 g + O2 g
why does lithium nitrate not follow the trend for the rest of the group 1 metal nitrates during thermal decomposition
-lithium nitrite is not thermally stable
-so will only reach thermal stability with the smaller oxide ion when lithium oxide is produced
explain what happens when group 2 nitrates are heated by a bunsen flame
E.g. magnesium nitrate
-group 2 nitrates undergo decomposition
-as you go down the group they are harder to decompose
-the oxide ion is produced rather than the nitrite ion because group 2 elements are smaller so still aren’t thermally stable with the smaller nitrite ion
-nitrogen dioxide gas and O2 gas are produced
2Mg(NO3)2 s = 2MgO s + NO2 g + O2 g
how are the terms polarising power, polarisability, polarise and polarised used
-cations have polarising power and can polarise anions
-anions show polarisability and can be polarised by cations
explain what affects polarising power
-ionic radius of the cation
-cations with a smaller radius are more polarising, they can approach closer to the anion
-charge of the cation
-cations with a higher positive charge are more polarising
explain what affects polarisability
-ionic radius of the anion
-anions with a larger ionic radius are polarised more readily, because the electrons are less tightly held
-charge of the anion
-anions with a higher negative charge are polarised more readily because there is more charge to be distorted
what is meant by an ionic bond with some covalency
-when the charge cloud of the anion is attracted to the cation
-the electrons in the anion charge cloud are distorted and pulled towards the cation
is aluminium chloride covalent or ionic
-AlCl3
-the bonding is partially covalent
-the aluminium cation is very polarising because it has a high positive charge and small ionic radius
-so readily polarises the large chloride anions
what colour are group 1 and 2 nitrates and carbonates
white solids
what happens when group 1 carbonates are heated using a bunsen flame
group 1 carbonates are stable at bunsen temperature
however lithium decomposes to form lithium oxide and carbon dioxide
what happens when group 2 carbonates are heated using a bunsen flame
e.g. magnesium
-all group 2 carbonates decompose
-they are more stable as you go down the group
MgCO3 s = MgO s + CO2 g
explain why group 2 carbonates become more stable as you go down the group
-when cations are small they can polarise the large carbonate anion
-when polarisation occurs there is greater covalent character
-so the cation is less stable to heat
-but as you go down group 2 the cations increase in ionic radius
-ionic character increases down the group
-so are more stable to heat
explain the trend in melting point and boiling point down group 7
-down group 7 mp and bp increases
-because the number of electrons in the electron cloud of the molecule increases
-so the attraction between the instantaneous dipole and induced dipole increase
-so more heat energy required to break the London forces between molecules
explain the trend in ionisation energy down group 7
-down group 7 ionisation energy decreases
-because atomic radius increases down the group, so the outer electrons is further from the nucleus, so the electrostatic attraction is weaker, so less energy is required to remove the outer electron
-shielding increases down the group, so the outer electron decreases in energy
-despite nuclear charge increasing down the group
what colour and state is bromine at room temperature
brown liquid
what colour and state is flourine at room temperature
pale yellow gas
what colour and state is chlorine at room temperature
green gas
what colour and state is iodine at room temperature
grey/black solid
what colour is iodine in gaseous state
purple
are chlorine, bromine, and iodine soluble in water
-yes, they make chlorine water and bromine water
-chlorine water is pale green
-bromine water is orange
-iodine is only slightly soluble in water
-iodine solution is pale brown
in what type of solvents are halogens most soluble
-in organic solvents (e.g. hexane)
-when an organic solvent is added to a solution containing a halogen, the coloured halogen is concentrated in the organic layer
what colour is a solution of iodine in hexane
purple
halogens are oxidising agents because they are reduced therefore oxidise other substances
explain the oxidising power trend down group 7
-down group 7 the halogens become weaker oxidising agents
-because their atomic radius is larger so the distance between the outer electron and nucleus is larger, so the electrostatic attraction is weaker, so its harder to gain electrons
-increased shielding also makes it harder to gain electrons
explain the reaction between chlorine and sodium hydroxide
-NaOH reduces the chlorine into chloride ions
-as the chloride ions are formed the solution is decolourised
-this is a disproportionation reaction
2NaOH + Cl2 = NaOCl + NaCl + H2O
the ionic equation is 2OH- + Cl2 = OCl- + Cl- + H2O
complete and explain this reaction
Cl2 + 2KI
-Cl2 + 2KI = 2KCl + I2
-this is a displacement reaction
-chlorine is a stronger oxidising agent so it oxidises the iodine forming I2
-so chlorine displaces the less reactive iodide ion
what 3 factors does electronegativity depend on
-nuclear charge, the bigger the nuclear charge the higher the electronegativity
-distance between the nucleus and bonding pair of electrons, the shorter the distance the greater the electronegativity
-shielding, the lower the shielding the greater the electronegativity
what is the equation for the reaction between chlorine and water
Cl2 + H2O = HCl + HOCl
-this is a disproportion reaction because chlorine is oxidised and reduced
-HCl and HOCl are both colourless acids
explain why chlorine is the most reactive halogen (except fluorine)
-it has the smallest atomic radius, so electrons are more strongly attracted to the nucleus
-it has the least shielding because it has the smallest number of complete inner energy levels of electrons, so incoming electrons experience less repulsion
what is the full equation and ionic equation for the reaction between cold sodium hydroxide and chlorine
full equation:
2NaOH + Cl2 = NaCl + NaOCl + H2O
NaOCl is sodium chlorate (I)
ionic equation:
2OH- + Cl2 = Cl- + OCl- + H2O
OCl- is the chlorate (I) ion
why is the reaction between cold sodium hydroxide and chlorine a disproportionation reaction
ionic equation:
2OH- + Cl2 = Cl- + OCl- + H2O
the reactant chlorine starts with an oxidation number of 0
chlorine is reduced to form the chloride ion 1- (Cl-)
and oxidised to form the chloride ion 1+ (OCl-)
what is the ionic equation for the reaction when a solution of chlorate (I) ions are heated
ionic equation
OCl- = OCl3- + Cl-
further disproportionation occurs producing chlorate (V) ions
what is the full equation and ionic equation for the reaction between hot sodium hydroxide and chlorine
full equation
6NaOH + 3Cl2 = 5NaCl + NaClO3 + 3H2O
NaClO3 is sodium chlorate (V)
ionic equation
6OH- + 3Cl2 = 5Cl- + ClO3- + 3H2O
ClO3 is the chlorate (V) ion
why is the reaction between hot sodium hydroxide and chlorine a disproportionation reaction
ionic equation
6OH- + 3Cl2 = 5Cl- + ClO3- + 3H2O
the reactant chlorine starts with an oxidation number of 0
chlorine is reduced to form the chloride ion 1- (Cl-)
and oxidised to form the chloride ion 5+ (OCl-)
why are halogens more soluble in hexane
-halogens are non-polar and forces between halide molecules are London forces
-hexane is non-polar and has London forces between molecules
-so because like dissolves like, the non-polar hexane will dissolve the non-polar halogen
describe the test for halides in a solution
-add nitric acid followed by silver nitrate to the sample
-the presence of silver chloride will give a white precipitate, silver bromide a cream precipitate and silver iodide a yellow precipitate
-further confirmatory tests can be done
-when dilute aqueous ammonia is added the silver chloride precipitate is soluble so it dissolves, the silver bromide and silver iodide precipitates are insoluble to don’t dissolve
-when concentrated aqueous ammonia is added silver chloride is soluble so will dissolve, silver iodide is insoluble so won’t dissolve
does sulfuric acid act as a reducing agent or oxidising agent
sulfuric acid is an oxidising agent
itself is reduced
what are the observations and products responsible for them, when concentrated sulfuric acid is added to sodium chloride
observation: steamy fumes, turns blue litmus paper red
product: HCl (g)
what are the observations and products responsible for them, when concentrated sulfuric acid is added to sodium bromide
HBr - steamy fumes
Br2 - orange fumes
SO2 - colourless gas
turns blue litmus paper red
what are the observations and products responsible for them, when concentrated sulfuric acid is added to sodium iodide
HI - steamy fumes
I2 - purple fumes or black solid
SO2 - colourless gas
S - yellow solid
H2S - colourless gas with rotten egg smell
what is the equation for the reaction between concentrated sulfuric acid and sodium chloride
is it a redox reaction?
-1 equation because this isn’t a redox reaction
-chloride ions have a low reducing power
-so the sulfuric acid only acts like an acid and not like an oxidising agent
NaCl + H2SO4 = NaHSO4 + HCl
what is the equation for the reaction between concentrated sulfuric acid and sodium bromide
is it a redox reaction?
-the equation for the formation of steamy fumes HBr:
NaBr + H2SO4 = NaHSO4 + HBr
-1 redox reaction occurs:
-this is the ionic equation for the formation of Br2
2Br- = Br2 + 2e-
-and the ionic equation for the formation of SO2
H2SO4 + 2H+ + 2e- = 2H2O + SO2
-when these 2 are put together it represents the equation for the oxidation of steamy fumes HBr
H2SO4 + 2HBr = Br2 + SO2 + 2H2O
during the test for halides in a solution why is nitric acid added
the nitric acid reacts with any other anions (e.g. carbonate ions)
so they don’t form a precipitate that would effect the results
what is the reaction between silver nitrate and sodium chloride
AgNO3 (aq) + NaCl (aq) = AgCl (s) + NaNO3 (aq)
what happens when hydrogen halides react with water
-when hydrogen halides react with water, they form colourless acidic solutions
what happens when hydrogen halides react with ammonia
-hydrogen halides and ammonia gas react to form salts
-the salts are white ionic solids
what is the equation for the reaction between ammonia and hydrogen bromide
NH3 (g) + HBr (g) = NH4Br (s)
What are the step to carry out a flame test
-dip a nichrome wire into a beaker of hydrochloric acid
-dip with nichrome wire into the powdered sample
-hold the nichrome wire in the Bunsen flame and observe the colour
When conducting flame tests what colour would indicate the presence of lithium ions
Red
When conducting flame tests what colour would indicate the presence of sodium ions
Yellow/orange
When conducting flame tests what colour would indicate the presence of potassium ions
Lilac
When conducting flame tests what colour would indicate the presence of rubidium ions
Red/purple
When conducting flame tests what colour would indicate the presence of caesium ions
Blue/violet
When conducting flame tests what colour would indicate the presence of beryllium ions
There is no colour
When conducting flame tests what colour would indicate the presence of magnesium ions
There is no colour
When conducting flame tests what colour would indicate the presence of calcium ions
Brick red
When conducting flame tests what colour would indicate the presence of strontium
Crimson red
When conducting flame tests what colour would indicate the presence of barium
Apple green
What are 2 limitations of flame tests to identify cations present in a compound
-there could be small traces of another cation that can mask other colours
-describing colours with words is subjective, people may interpret the colours differently
Describe the test for ammonium ions
-add sodium hydroxide to the sample
-heat the mixture
-hold damp red litmus paper at the neck of the test tube to test the gas produced
-if the litmus paper turns blue, it indicates the presence of ammonia gas, which is an alkaline gas
NH4+ + OH- = NH3 + H2O
What is the equation for the reaction between ammonia and hydrogen chloride gas
What observations can be seen
NH3 + HCl = NH4Cl
Ammonium chloride forms white fumes
This is a test for the presence of ammonium ions
Describe the burning test for organic analysis
-use a pipette to place a few drops of the sample onto a copper can lid
-in a fume cupboard light a splint and ignite the lid
-observe the type of flame given off
State the inference for burning organic analysis
Orange clean flame = saturated
Orange sooty flame = unsaturated
Blue clean flame = alcohol
State the inference for the organic analysis of dissolving in distilled water
Dissolves = polar molecule that can make hydrogen bonds
Doesn’t dissolve (forms layers) = non polar molecule
State the inference for the organic analysis of the test with bromine water
Solution decolourises, changes from orange to colourless = double c=c bond present
No change = no c=c bond present
State the inference for the organic analysis of the test with acidified potassium manganate
Decolourises the solution from purple to colourless (possible brown precipitate) = C=C bond present
No change = no c=c bond present
State the inference for the organic analysis of adding solid sodium to the sample
Effervescence, sodium dissolves, white solid formed = alcohol
State the inference for the organic analysis of the test with sodium/potassium dichromate
Orange solution turns to a green solution = primary or secondary alcohol or aldehyde
State the inference for the organic analysis for the reaction with phosphorous pentachloride
Steamy fumes evolved which turn damp blue litmus paper red = OH group present (possibly an alcohol or carboxylic acid
State the inference for the organic analysis of the reaction with Brady’s solution
Orange solution changes to an orange/yellow precipitate = aldehyde or ketone
State the inference for the inorganic analysis for the reaction with sodium hydroxide
This is a test to identify present cations
Group 1 cations = no precipitate formed
Group 2 cations = white precipitate formed, as you go down the group the precipitate will be more soluble
The precipitates for all cations below aluminium dissolve in excess NaOH
The reaction between NaOH and warm ammonium ions produces ammonia gas, which can be identifies by using damp red litmus paper turning blue
Describe the test with NaOH to identify present cations for inorganic analysis
Add a few drops of NaOH to the sample in a test tube
Determine if a precipitate has formed
Add a more drops of NaOH so that it’s in excess
Determine if the precipitate has dissolved
Describe the test for sulphate ions in inorganic analysis
State the inference
Add barium chloride and hydrochloric acid
Sulphate ions present = white precipitate
Barium nitrate + nitric acid
Describe the test to identify if nitrate ions are present in inorganic analysis
State the inference
Heat the sample using a Bunsen flame, so that it undergoes thermal decomposition
Group 2 nitrates and lithium nitrate = NO2 gas evolved, brown fumes will be seen
Describe the test for the presence of carbonate or hydrogen carbonate ions in inorganic analysis
State the inference
Add hydrochloric acid to the sample
Set up a delivery tube going into a test tube with limewater
A positive test will produce effervescence in the test tube with hydrochloric acid and turn the limewater from colourless to cloudy
State the inference for the test between concentrated sulfuric acid and halides
Cl- ions = steamy fumes
Br- ions = steamy fumes, orange/brown gas
I- ions present= steamy fumes, purple fumes, grey/black solid, yellow solid, rotten egg smell
Describe the burning teet
