Chemistry Revision!

Nothing to do, so I shall post everything that I’ve memorised! They are all based on my memory, gigglez. Read more if you’re interested!

Periodic Table

• Actual Nuclear Charge (total protons) – increase across period, increase down group
• No of shielding (non-valence) electrons – constant across period, increase down group
• Effective Nuclear Charge – increase across period, constant down group
• Atomic radii – decrease across period (across period, there are more protons, so stronger nuclear pull), increase down group (down group, there are more shells and hence more shielding electrons)
• Ionisation energies – increase across period (stronger nuclear pull due to decreasing atomic radii), decrease down group (weaker nuclear pull due to increasing atomic radii)
• Electronegativity – same as Ionisation energies
• Melting/Boiling Points – decrease down Metal groups (Atomic radii increases, weaker nuclear pull, weaker bonds), increase down Non-metal groups (Molecular mass increases, stronger intermolecular forces)
• Group I metals – density increases down group, (low) mp decreases down group, reactivity increases down group, [2Na + H2O -> Na2O + H2]
• Halogens – colour becomes darker down group, gas to liquid to solid down group, reactivity decreases down group, more reactive metal displaces less reactive metal, [Cl + 2I- -> Cl- + I2]
• Noble gases – density increases down group, mp increases down group
• Transition metals – variable oxidation states, high mp/bp.

Salt Preparation

• Precipitation for insoluble salts
• Titration for Group I and NH4 salts (soluble)
• Acid + excess insoluble carbonates/hydroxides/oxides for all other soluble salts
• Acid + excess metal for all other soluble salts except Lead(II), Copper(II) and Silver salts.

Qualitative Analysis

• Test for Cations
  • Al(3+) – aq. NaOH [white ppt soluble in excess to form colourless solution], aq. NH4OH [white ppt insoluble in excess]
  • Pb(2+) – same as Al(3+)
  • Zn(2+) – aq. NaOH and aq. NH4OH [white ppt soluble in excess to form colourless solution]
  • Ca(2+) – aq. NaOH [white ppt soluble in excess to form colourless solution], aq. NH4OH [no ppt]
  • Cu(2+) – aq. NaOH [light blue ppt insoluble in excess], aq. NH4OH [light blue ppt soluble in excess to form dark blue solution]
  • Fe(2+) – aq. NaOH and aq. NH4OH [green ppt insoluble in excess]
  • Fe(3+) – aq. NaOH and aq. NH4OH [red-brown ppt insoluble in excess]
  • NH4(-) – aq. NaOH [ammonia produced on warming]
• Test for Anions
  • CO3(2-) – acid [CO2 produced] (can be tested using Ag(+), Ba(2+) and Pb(2+), white ppt)
  • SO4(2-) – Ba(NO3)2 and dilute HNO3 [white ppt insoluble in excess HNO3] (can be tested using Ba(2+) and Pb(2+), white ppt)
  • Cl(-) – Ag(NO3)2 and dilute HNO3 [white ppt insoluble in excess HNO3] (can be tested using Ag(+) and Pb(2+), white ppt)
  • I(-) – Ag(NO3)2 and dilute HNO3 [pale yellow ppt insoluble in excess HNO3] (can be tested using Ag(+)and Pb(2+), yellow ppt)
  • NO3(-) – aq. NaOH and aluminum [ammonia produced on warming]
• Test for Gases
  • NH3 – turns damp litmus paper blue
  • H2 – extinguishes lighted splint with ‘pop’ sound
  • O2 – relights glowing splint
  • Cl2 – bleaches damp litmus paper
  • CO2 – turns limewater chalky

Reactivity Series of Metal

• K, Na, Ca, Mg, Al, Zn, Fe, (Sn), Pb, (H), Cu, Hg, Ag, Au
• Heat + Oxygen
  • K, Na – forms oxide in limited supply, forms peroxide in excess
  • Ca to Fe – burns to form oxides
  • Pb to Hg – does not burn, surface oxidises
  • Ag, Au – nothing happens
• Heat + Chlorine – all become chlorides with decreasing vigour
• Reaction with cold water (K to Mg – displaces H2 in decreasing vigour)
• Reaction with steam (K to Fe – displaces H2 in decreasing vigour)
• Reaction with acids (K to Pb – displaces H2 in decreasing vigour)
• Decreasing ability as a reducing agent
• Displaces the metals below in the series
• Heat on oxides
  • K to Hg – Stable to heat
  • Ag, Au – decomposes to metal
• Heat on hydroxides
  • K, Na – Stable to heat
  • Ca to Hg – decomposes to oxide + H2
  • Ag, Au – decomposes to metal + H2 + O2
• Heat on carbonates
  • K, Na – Stable to heat
  • Ca to Hg – decomposes to oxide + CO2
  • Ag, Au – decomposes to metal + CO2 + O2
• Heat on nitrates
  • K, Na – decomposes to nitrite + O2
  • Ca to Hg – decomposes to oxide + NO2 + O2
  • Ag, Au – decomposes to metal + NO2 + O2
• Solubility of oxides
  • K, Na – dissolves into hydroxide
  • Ca to Au – insoluble
• Solubility of chlorides
  • K to Cu – soluble except Pb(Cl)2 which dissolves in hot water only
  • Hg to Au – insoluble
• Rusting of iron
  • Fe -> Fe(2+) + 2e(-)
  • O2 + 2H2O + 4e(-) -> 4OH(-)
  • Fe(2+) -> Fe(3+) + e(-)
  • Fe(3+) + 3OH(-) -> FeOH3
  • FeOH3 + [O] -> Fe2O3 . xH2O

Metal Extraction

• C + O2 -> CO2
• CO2 + C -> 2CO
• Fe2O3 + 3CO -> 2Fe + 3CO2
• CaCO3 -> CaO + CO2
• CaO + SiO2 -> CaSiO3 (slag)

Electric Cell

• Negative electrode – more reactive metal, oxidisation of metal
• Positive electrode – less reactive metal, reduction of cations in electrolyte
• The further apart the two metals are in the reactivity series, the larger the voltage