Summary Pearson Edexcel A Level Chemistry (Year 1 and Year 2) - Unit 4 - Inorganic Chemistry and the Periodic Table (9CH0)

4 - Inorganic chemistry & the periodic table
●​ ***s-block (+) compounds tend to be colourless​
Ions of transition metals tend to have colours


Group 2 elements (alkali earth metals)/Group 1 (alkali metals)
●​ See reactivity




●​


Solubility
●​ ***Hydroxides (OH-): more soluble down group, sulphates (SO42-): less soluble down
group

Sulphates (SO42-)




●​
○​ When lattice energy > hydration energy, compound doesn’t dissolve (∴
CaSO4 is sparingly soluble)
○​ Solubility decreases down group as larger cations have lower charge
densities and so less attracted to water




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, Hydroxides (OH-)
●​ Larger cations down group, ∴ increasing coordination number for more water
molecules to fit in...
●​ ***Group 2 hydroxides have higher pH down group (ie increasing basic strength)


Reactions (Mg as eg for Group 2, Na ```` 1, Cl2 as common halogen)

Metal-acid
●​ Group 2: Mg (s) + 2 HCl (aq) → MgCl2 (s) + H2 (g)
●​ Group 1: 2Na (s) + 2 HCl (aq) → 2NaCl (s) + H2 (g)

Metal-oxygen
●​ Group 2: 2Mg (s) + O2 (g) → 2MgO (s)
●​ Group 1: 4Na (s) + O2 (g) → 2Na2O (s)

Metal-water
●​ ***With H2O: cold - produces OH-, hot - produces O2-
●​ Group 2: Mg (s) + 2H2O (l) → Mg(OH)2 (aq) + H2 (g)​
Mg (s) + H2O (g) → MgO (s) + H2 (g)
●​ Group 1: 2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)​
2Na (s) + H2O (g) → Na2O (s) + H2 (g)

Metal-halogen
●​ Group 2: Mg (s) + Cl2 (g) → MgCl2 (s)
●​ Group 1: 2Na (s) + Cl2 (g) → 2NaCl (s)

Metal oxide-water
●​ Group 2: MgO (s) + H2O (l) → Mg(OH)2 (aq)
●​ Group 1: Na2O (s) + H2O (l) → 2NaOH (aq)

Metal oxide-acid (acid-base)
●​ Group 2: MgO (s) + 2HCl (aq) → MgCl2 (s) + H2O (l)
●​ Group 1: Na2O (s) + 2HCl (aq) → NaCl (s) + H2O (l)

Metal hydroxide-acid (acid-base)
●​ Group 2: Mg(OH)2 (s) + 2HCl (aq) → MgCl2 (s) + 2H2O (l)
●​ Group 1: NaOH (aq) (s) + HCl (aq) → NaCl (s) + H2O (l)

Thermal decomposition
●​ ***Thermal stability increases down group
●​ Carbonates (CO32-)
○​ Group 2: MgCO3 (s) → MgO (s) + CO2 (g)
○​ Group 1 (Li ONLY): Li2CO3 (s) → Li2O (s) + CO2 (g)
●​ Nitrates (NO3-) - N in nitrate is being reduced (ox: +5 → +4)



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