1796f_PChem Revision Notes 1

# 1796f_PChem Revision Notes 1 - Raffles Junior College H2...

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1 1) Know the definitions! (i) Relative Atomic Mass based on the 12 C scale. (ii) Relative Isotopic Mass based on the 12 C scale. (iii) Relative Molecular Mass based on the 12 C scale. (iv) Relative Formula Mass based on the 12 C scale. (v) Mole (vi) Empirical and Molecular formula 2) Be able to calculate the relative atomic mass (A r ) of an element given the relative abundances of its isotopes. Average A r = abundance x A r of isotope + abundance x A r of isotope + ……. ------------------------------------------------------------------------------------- Total abundance 3) Calculate empirical and molecular formulae using combustion data or composition by mass. For combustion of hydrocarbons: C x H y + (x + y/4)O 2 b xCO 2 + (y/2)H 2 O Be careful when approximating after obtaining the ratio. E.g. 1.2 : 1 = 6 : 5 1.25 : 1 = 5 : 4 1.33 : 1 = 4 : 3 1.5 : 1 = 3 : 2 1.67 : 1 = 5 : 3 1.75 : 1 = 7 : 4 In general, multiply by suitable factor to get nearest whole number. Ending no. .2 .25 .33 .5 .67 .75 Multiply by 5 4 3 2 3 4 4) Write and /or construct balanced equations and perform calculations using mole ratios. Identify the limiting reagent! 1 mole of gas at r.t.p. and s.t.p. occupies 24 dm 3 and 22.4 dm 3 respectively. No. of moles = mass/molar mass Concentration in mol dm -3 = no. of moles/volume of solution in dm 3 Concentration in g dm -3 = mass/volume of solution in dm 3 5) 1 mole of a species contains 6.02 x 10 23 particles of that species. 1 mole of NH 3 contains 1 mole of N atoms and 3 moles of H atoms, 6.02 x 10 23 N atoms and 3 x 6.02 x 10 23 H atoms. 6) Be familiar with the following terminology: Sulphate/ sulphate (VI) SO 4 2- Nitrate/ nitrate (V) NO 3 - Sulphite/ sulphate (IV) SO 3 2- Nitrite/ nitrite (III) NO 2 - Sulphur trioxide SO 3 Nitrogen dioxide NO 2 Sulphuric Acid H 2 SO 4 Nitric Acid HNO 3 Sulphurous Acid H 2 SO 3 Nitrous Acid HNO 2 Chromate (VI) CrO 4 2- Dichromate (VI) Cr 2 O 7 2- Manganate (VII) MnO 4 - Manganese (II) Mn 2+ Raffles Junior College H2 Chemistry 2008/9 Physical Chemistry Revision Part 1 (Stoichiometry, Chemical Bonding, Gaseous State, Chemical Kinetics and Chemical Energetics)

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2 7) Be able to write balanced redox equations. (even if you’ve never seen the species before) To write a balanced half -equation: Step 1 : Balance the element other than O and H. Step 2 : Balance O using H 2 O . Step 3 : Balance H using H + . Step 4 : Add equal no. of moles of OH - on both sides of half equation so as to completely neutralize all H + . (Step 4 is used only if in alkali/neutral conditions) Step 5 : Balance charges using electrons . 8) Be familiar with these various common titrations. E.g.
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1796f_PChem Revision Notes 1 - Raffles Junior College H2...

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