Berry Chemistry Form 6 Definition List Part 2

by BerryBerryTeacher

in Berry Reference (Notes)

This is the second list of your berry important definitions for STPM Form 6 Chemistry. Remember, reciting them many times will help you to remember them for the exams, understanding them will enable you to remember them for life. Share this berry essential definitions with your friends.

STPM Chemistry Form 6 Definition List – Part 2:

Acid-Base Equilibria

Term Definition Example
Arrhenius acid Yields H3O+ when added to H2O aq: [H3O+] > [OH-]
Arrhenius base Yields OH- when added to H2O aq: [OH-] > [H3O+]
Bronsted-Lowry acid Proton donor HX in protic solvent
Bronsted-Lowry base Proton acceptor KOH in protic solvent
Lewis acid Electron pair acceptor BF3 in aprotic solvent
Lewis base Electron pair donor NH3 in aprotic solvent

Four important concepts (just the berry essence):

  1. Acid dissociation – (expressed quantitatively) acid dissociation constant, Ka, is nothing more than the equilibrium constant for the dissociation reaction of an acid in water.
    Relative strength of an acid ↑­ (increases), its Ka ↑­ (increases) and its pKa ↓(decreases).
    (The Ka and pKa of an acid depend on the strength of an acid, but not its concentration.)
  2. Base hydrolysis – base hydrolysis constant, Kb, nothing more than the equilibrium constant for the hydrolysis reaction of a base in water.
    Relative strength of a base ­ ↑­ (increases), its Kb ­ ↑­ (increases) and its pKb ↓ (decreases).
    (The Kb and pKb of an acid depend on the strength of an acid, but not its concentration.)
  3. Overall Relationship : Acid strength ­↑­, Ka ­↑­, pKa ↓­, conjugate base strength ↓, Kb ↓, pKb ↑­
  4. Strength of a reagent (Ka / pKa and Kb / pKb) – the completeness of a reaction in water. (dissociation = ionisation or electrolytic nature)
    The stronger the acid, the more electrolytic it is, because it conducts electricity better due to the greater number of ions in solution.
    The stronger the base, the more readily it undergoes hydrolysis when mixed with water

­

Acid Name pKa
Cl3CCOOH Trichloroacetic acid 0.64
Cl2HCCOOH Dichloroacetic acid 1.27
H2SO3 Sulfurous acid 1.82
HClO2 Chloroacetic acid 1.90
ClH2CCOOH Chloroacetic acid 2.82
HF Hydrofluoric acid 3.15
HNO2 Nitrous acid 3.41
HCOOH Formic acid 3.74
H3CCOOH Acetic acid 4.74
2,4-(H3C)2C6H3NH3+ 2,4-dimethylanilinium 5.08
4-H2NC6H4NH3+ 4-aminoanilinium 6.18
H3CO3 Carbonic acid 6.36
4-O2NC6H4OH 4-nitrophenol 7.15
HClO Hypochlorous acid 7.46
HBrO Hypobromous acid 8.72
NH4+ Ammonium 9.26
HCN Hydrogen cyanide 9.36
HIO Hypoiodous acid 10.66

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