Topic 4 - Inorganic Chemistry and Periodic Table Flashcards
How does the reactivity change down group 2?
increases
Why does the reactivity increase down group 2?
- more electrons/electron shells
- outer electrons further from nucleus
- weaker electrostatic attraction between nucleus and outer electrons
- less energy required to remove electrons
How does the ionisation energy change down group 2?
decreases
Why does the ionisation energy decrease down group 2?
- more electrons/electron shells
- outer electrons further from nucleus
- weaker electrostatic attraction between nucleus and outer electrons
- less energy required to remove electrons
How does the atomic radii change down group 2?
increases
Why does the atomic radii increase down group 2?
- more electrons
- more electron shells
How does the solubility of sulphates change down group 2?
decrease
How does the solubility of hydroxides change down group 2?
increase
group 2 metal + oxygen ->
metal oxide
white solid
group 2 metal + water ->
liquid water
metal hydroxide + hydrogen
group 2 metal + water ->
steam
metal oxide + hydrogen
group 2 metal + chlorine ->
metal chloride
white solid
group 2 oxide + water ->
metal hydroxide
thermal decomposition of group 2 carbonates (and Li2CO3)
carbonates ->
metal oxide + carbon dioxide
thermal decomposition of group 1 nitrates (except LiNO3)
nitrate ->
metal oxide + nitrogen dioxide
What is thermal decomposition?
breaks down of a substance into two or more substances due to heat
What is thermal stability?
likelyhood of a substance to undergo a change at a particular temperature
-how easily a substance breaks down under heat
thermal decomposition of group 1 nitrates (except Li2NO3)
nitrate ->
XNO3
group 1 nitrate + oxygen
XNO2 +1/2 O2
thermal decomposition of group 2 nitrates
nitrate ->
X(NO3)2
metal oxide + nitrogen dioxide + oxygen
XO + 2NO2 + 1/2 O2
How do group 1 and 2 nitrates and carbonates change in thermal stability down the group?
increase in thermal stability
-require a higher temperature to thermally decompose
Describe the change in thermal stability down the group (1 or 2)
-ionic radii decreases (-more energy levels)
-volume of ion increases
-charge remains constant
∴ charge density decreases
-have less of a polarising power on negative ions
-cause less distortion of electron cloud
-higher thermal stability
Describe the change in thermal stability across a period
- same period ∴ same number of energy levels
- group further to right has more protons -greater nuclear charge so greater electrostatic attraction between nucleus and outer electrons
- group 2 ions have higher charge and lower volume than group 1 ions ∴ higher charge density
- cause more distortion of electron cloud of negative ion
- lower thermal stability
What are the three aspects to Fajan’s rules that allow us to predict a compound’s distortion of electron density?
- high charge of cation (+ve ion)
- small cation (+ve ion)
- large anion (-ve ion)
What does a higher charge and smaller ionic radii result in?
- higher charge density
- more distortion of electron density
- less thermally stable
Describe the method of a flame test
- nichrome wire loop is dipped into concentrated HCl and in the flame to clean it
- dipped back in HCl and then into the sample
- sample is held in flame and flame colour is observed
What is the flame colour of Li+?
red
What is the flame colour of Ca2+?
orange red (brick red)
What is the flame colour of Sr2+?
deep red
What is the flame colour of Ba2+?
pale green (yellow green)
Describe how an emission spectra works
- electrons absorb specific wavelengths of light so get excited and are promoted to a higher energy level
- electrons then go back to their ground state and release wavelengths of energy equivalent to the gap of energy levels
- wavelength of light emitted is seen as a flame or as an emission spectra
How do melting and boiling points change down group 7?
increase
Why do melting and boiling points increase down group 7?
- have more electrons
- therefore have stronger London forces
- requires more energy to overcome IMF so mp/bps increase
How does electronegativity change down group 7?
decreases
Why does electronegativity decrease down group 7?
- more electrons
- more shielding
- outer electrons further from nucleus
- less nuclear attraction
How does reactivity change down group 7?
decreases
Why does reactivity decrease down group 7?
- more electrons
- more shielding
- outer electrons further from nucleus
- less nuclear attraction so harder to gain an electron
How does atomic radii change down group 7?
increase
Why does atomic radii increase down group 7?
- more electrons and more energy levels
- more shielding
- outer electrons further from nucleus
- less nuclear attraction
How does oxidising power change down group 7?
decreases
How does the reducing power of halides change?
increases down group
general reaction of halogens in cold NaOH
X2 + 2NaOH ->
NaXO + NaX + H2O
halogen + group 1/2 metal ->
halide salt (eg. NaCl)
Why does chlorine make water safe to drink/swim in?
Chlorine reacts with water in a disproportionation reaction to produce hypochloride
-hypochloride ionises to make chlorate ions (ClO-) which kill bacteria
halogen + iron ->
iron halide
FeX3 (for strong oxidising agents -Cl and Br)
(FeI2 for iodine as it is a weaker oxidising agent so can only remove one electron)
halogen + metal halide ->
halogen + metal halide
displacement reaction
halide salt + sulfuric acid (H2SO4) ->
depends on reducing ability of halide
generally: NaHSO4 + HX
(with strong reducing agents like iodide, HX then reacts with acid again to form hydrogen sulfide (H2S), halogen and water)
halide + silver nitrate solution ->
AgNO3 + NaX ->
silver halide + sodium nitrate
AgX + NaNO3
What colour precipitate do chloride ions form with silver nitrate?
white precipitate
What colour precipitate do bromide ions form with silver nitrate?
cream precipitate
What colour precipitate do iodide ions form with silver nitrate?
yellow precipitate
Ag+(aq) + X-(aq) ->
AgX (s)
Does silver chloride redissolve in ammonia solution? (NH3)
Yes, both in dilute and concentrated NH3
Does silver bromide redissolve in ammonia solution? (NH3)
Doesn’t in dilute NH3 but does redissolve in concentrated NH3
Does silver iodide redissolve in ammonia solution? (NH3)
Doesn’t redissolve in dilute or concentrated NH3
How can you test for halide ions?
- add silver nitrate solution (AgNO3) and observe colour of precipitate formed (white = Cl, cream = Br, yellow = I)
- add ammonia (NH3) (Cl will redissolve in dilute NH3, Cl and Br will redissolve in concentrated NH3)
hydrogen halide in water
dissolves
forms H+ and X-
hydrogen halide + ammonia ->
HX + NH3 ->
ammonium halide
NH4X
(white fumes)
How do you test for carbonate ions(CO3 2-)?
add dilute HCl
positive result: effervescence (fizzing) from carbon dioxide produced
-can test carbon dioxide by bubbling it through lime water using a delivery tube -will turn lime water cloudy
How do you test for sulfate ions (SO4 2-)?
add dilute HCl (to remove any carbonate ions) followed by barium chloride solution (BaCl2)
positive result: white precipitate formed (BaSO4)
How do you test for ammonium ions (NH4+)?
add sodium hydroxide solution
warm
positive result: produces ammonia (NH3)
-ammonia turns damp red litmus paper blue
-float a glass rod (previously dipped in HCl) and a white dense smoke will be produced (NH4Cl)
