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  1. 1. STPM Chemistry Form 6 Definition List: 1. The Hund Rule ± orbital with the same energy level (degenerate orbitals), electron will occupy different orbital singly/one electron first with the parallel spin, before pairing.(Reject: same spin, spin with same direction) STPM 2008, 2007 2. Pauli Exclusive Principle ± Each orbital can hold a maximum of two electrons with opposite spin. (Reject: different spin) STPM 2007 3. Aufbau principle ± Electrons occupy orbitals with the lowest energy level first. (Reject: occupy lower energy first) STPM 2006, 2007 4. Vapour pressure ± the pressure exerted by a vapour that is in equilibrium with its liquid at a fixed temperature in a closed system. It is due to the collision of the vapour particles on the walls of the container. STPM 2004STOICHIOMETRY 1. Molarity (M) [concentration of a fluid solution] ± defined as the moles of a solute per volume of solution. 2. Density [concentration of a fluid solution] ± defined as the mass of solution per volume of solution. 3. Dilution ± addition of solvent to a solution resulting in an increase in the volume of the solution and a decrease in the concentration of the solute in solution. 4. Precipitation reaction (also refer to as double-displacement reaction) ± a reaction that involve two aqueous salts being added together to form ions and a solid salt precipitate.ACID-BASE EQUILIBRIA 1. Arrhenius acid ± acid yields H3O+ when added to water 2. Arrhenius base ± base yields OH- when added to water 3. Bronsted-Lowry acid (proton donor) ± a substance that donate a proton, H+ to a base. 4. Bronsted-Lowry base (proton acceptor) ± a substance that accept a proton, H+ from an acid. 5. Conjugate acid ± a species (molecule or ion) formed when a proton is added to a base. 6. Conjugate base ± a species (molecule or ion) formed when a proton is removed from an acid. 7. Lewis acid ± an electron-pair acceptor. 8. Lewis base ± an electron-pair donor. 9. Electrolyte (also electrolytic conductor) ± a chemical compound that will conduct electricity in the molten state or in aqueous solution. 10. Strong acid ± an acid that is almost completely dissociated in aqueous solution. (Stronger the acid, the weaker its conjugate base) 11. Weak acid ± an acid that is only partially dissociated in aqueous solution. (Weaker the acid, the stronger its conjugate base)
  2. 2. STPM Chemistry Form 6 Definition List ± Part 2:Acid-Base EquilibriaTerm Definition ExampleArrhenius acid Yields H3O+ when added to aq: [H3O+] > [OH-] H2OArrhenius base Yields OH- when added to aq: [OH-] > [H3O+] H2OBronsted-Lowry acid Proton donor HX in protic solventBronsted-Lowry base Proton acceptor KOH in protic solventLewis acid Electron pair acceptor BF3 in aprotic solventLewis base Electron pair donor NH3 in aprotic solventFour 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 waterAcid Name pKaCl3CCOOH Trichloroacetic acid 0.64Cl2HCCOOH Dichloroacetic acid 1.27H2SO3 Sulfurous acid 1.82HClO2 Chloroacetic acid 1.90ClH2CCOOH Chloroacetic acid 2.82HF Hydrofluoric acid 3.15HNO2 Nitrous acid 3.41HCOOH Formic acid 3.74H3CCOOH Acetic acid 4.74
  3. 3. 2,4-(H3C)2C6H3NH3+ 2,4-dimethylanilinium 5.084-H2NC6H4NH3+ 4-aminoanilinium 6.18H3CO3 Carbonic acid 6.364-O2NC6H4OH 4-nitrophenol 7.15HClO Hypochlorous acid 7.46HBrO Hypobromous acid 8.72NH4+ Ammonium 9.26HCN Hydrogen cyanide 9.36HIO Hypoiodous acid 10.66