QCE Chemistry. Year 2016 Mark 0.00 Pages 40 Published Jan 5, Year 12 Chemistry. By Christopher (99.85 ATAR)

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1 QCE Chemistry Year 2016 Mark 0.00 Pages 40 Published Jan 5, 2017 Year 12 Chemistry By Christopher (99.85 ATAR)

2 Powered by TCPDF ( Your notes author, Christopher. Christopher achieved an ATAR of in 2016 while attending Matthew Flinders College Currently studying Bachelor of Science at University of Melbourne Achievements: Dux ATAR Distinction in ICAS Science OP1 High Distinction in ICAS Mathematics Five SAI 400's Distinction in Australian Mathematics Tournament Christopher says: Some of my academic achievements include achieving four A+ (in Biology, Chemistry, Mathematics B and Modern History) and a high A (VHA7) in English and Mathematics C at the end of Year 12, in which I scored an SAI 400 (top of the class) in all subjects excluding English. I also achieved Dux of the College. I enjoy mathematics, swimming, science, reading and to socialise with my friends! I achieved an OP1 / ATAR in Year 12.

3 Balancing Redox Reactions - An OXIDATION NUMBER is a number assigned to an element in chemical combination which represents the number of electrons lost (or gained, if the number is negative) by an atom of that element in the compound. - In a redox reaction, each species is given an oxidation number depending on its state in the solution. - Rules for assigning oxidation numbers: 1. All free elements = 0 (solids, gases) 2. Simple ions have a number = the ion charge (Na+ = +1) 3. Oxygen = -2 (except in peroxides, where it is -1) 4. Hydrogen = +1 (except in metal hydrides where it is -1) 5. The sum of the oxidation number = 0 in a neutral compound 6. The sum of the oxidation numbers in a polyatomic ion = charge on ion 7. The most electronegative element in a neutral compound has the negative oxidation number - In a reaction, oxidation occurs when an element has had an increase in oxidation number. - Reduction occurs when an element has had a decrease in oxidation number. - To balance redox reactions: 1. Separate into TWO half equations. 2. Balance all atoms except hydrogen and oxygen. 3. Calculate the oxidation numbers and balance the charge with the correct electron numbers. 4. Balance the oxygen by adding water to the appropriate side. 5. Balance the hydrogen by adding hydrogen ions to the appropriate side. 6. Balance the electrons to be the same in both half equations. 7. Add both half equations together.

4 - Another way to balance redox reactions is to build SKELETON HALF EQUATIONS. - The following steps are: 1. Balance all elements except oxygen and hydrogen. 2. Balance the oxygen by adding water to the appropriate side. 3. Balance hydrogen by adding hydrogen ions to the appropriate side. 4. Balance the charges by adding electrons to the appropriate side. 5. Balance the electrons in each half equation. 6. Add the half equations together.

5 Powered by TCPDF ( Disproportionation & Basic/Acidic Solutions - In DISPROPORTIONATION REACTIONS, a species is simultaneously oxidised and reduced to form two different products. - This mostly occurs with oxides of metals in Group V and VII when their oxidation number begins as an even number. It also occurs with many transition metal complexes. - If the reaction is said to be in an ACIDIC solution, it needs to be verified that the balanced equation has aqueous hydrogen ions on the reactants side (it usually does). - If the reaction is said to take place in a BASIC (ALKALINE) solution the aqueous hydrogen ions need to be cancelled out by adding the correct number of aqueous hydroxide ions to both sides of the equation. The hydrogen ion and hydroxide ion will form water. This may then be cancelled out with any equal amounts of water on the other side of the equation. Limitations of Calculating Cell Voltage - The standard electrode potentials can only be used to calculate cell potential if standard conditions are used. - Any changes to SLC will cause a change in the voltage and can even change the order of half cells in the electrochemical series. - Electrochemical series doesn t give any information about the rate of reaction. - If the solutions are acidic or basic, very hot or cold, then the reactions may change. - The Nernst equation is useful to predict the voltage when concentrations are changed. - Note that a positive cell potential indicates that the ell will go spontaneously in the direction as written (i.e. act as a galvanic/voltaic cell).