chem

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Chemistry These are some of my chemistry notes from CHEM1201 (Chemistry 1B), a first year chemistry subject at the University of New South Wales.

There are two reasons why I have these here:

For my friends who do not attend lectures and are always asking to copy my notes anyway, so now you can all get them off the web
For my own revision: the act of organising these notes and typing them helps me remember at least some of it.

So unless you are crazy, you probably won't find any of this very interesting.

The textbook used is by Silberberg; Chemistry: The Molecular Nature of Matter and Change. (Mosby, 1996)

Lecture Notes: Tuesday 13th October, 1998.

COMPLEX ION EQUILIBRIA

Formation constant = Stability constant

M + nL <=> ML_n note - complex formation involves ligand exchange as water is usually coorinated to the metal ion (eg M(H₂O)_n ⁿ⁺) but water is often not written. K_f = [ML_n] / [M][L]ⁿ Dissociation constant K_d = 1 / K_f SOLUBILITY and COMPLEX FORMATION CONSTANTS

Complex formation greatly increases the solubility of a metal salt, because it reduces [Mⁿ⁺_(aq)], the concentration of "free" metal ions in solution.

Example Questions:

1. Calculate [Ag⁺] when 0.0005M AgNO₃ is treated with 0.011M KCN.
K_f Ag(CN)₂^- = 5.56 * 10^-18

2. Calculate [Ag⁺] when 0.010M AgNO₃is treated with 0.80M NH₃ solution.
K_fAg(NH₃)₂⁺ = 10⁷

Lecture Notes: Monday, 19th October, 1998.

Complex formation increases the solubility of sparingly soluble salts.

Example Questions:

3. Calculate the solubility of AgBr in a) pure water and b) 0.4M NH₃ solution.
K_sp AgBr = 5.0 * 10^-13
K_f Ag(NH₃)₂⁺ = 1.6 * 10⁷

ELECTROCHEMISTRY

Oxidation and Reduction Reactions

OXIDATION:

electrons are lost
oxidation number increases

REDUCTION:

electrons are gained
oxidation number decreases

Oxidation and Reduction occur simultaneously.

Oxidising Agent (Oxidant):
reagent which causes another species to be oxidised; is reduced in doing so.

Reducing Agent (Reductant):
reagent which reduces another species; is oxidised in the process.

Redox Reaction involve changes in oxidation state.

OXIDATION STATE (NUMBERS)

Oxidation Numbers (ON) are a formalism, used to assist in assigning and balancing redox equations. (They do not really exist).

ON = charge on atoms if the compound was purely ionic (ie the electrons in covalent bonds go to the more electronegative atom.)

Rules for Assigning Oxidation Numbers are on page 155 of Silberberg (I refuse to type these stupid things out. Everyone knows them anyway.)