dojo study club comb chem wa2 revision guide

Dojo Study Club Combined Chemistry WA2 Revision Guide

Definitions Exothermic Reaction A reaction in which heat (energy) is given out to the surroundings. Endothermic Reaction A reaction in which heat (energy) is absorbed by the surroundings. Redox Reaction A reaction in which both reduction and oxidation take place. Oxidation A substance in oxidised when it gains oxygen in a chemical reaction. Reduction A substance is reduced when it loses oxygen in a chemical reaction. Oxidising Agent A substance that causes another reactant to go through oxidation, while undergoing reduction themselves. Reducing Agent A substance that causes another reactant to go through reduction, while undergoing oxidation themselves. Redox

Redox OIL RIG Oxidation Is Loss (electrons) Gain of Oxygen Loss of Hydrogen Loss of Electrons Increase in Oxidation State Reduction Is Gain (electrons) Loss of Oxygen Gain of Hydrogen Gain of Electrons Decrease in Oxidation State Oxidation Reduction “Good Guy” / Selfless Gets reduced itself, while oxidising others Oxidising Agent Reducing Agent “Bad Guy” / Selfish Gets oxidised itself, while reducing others

Rate Of Reaction The speed at which reactants are converted into products, per unit time Concentration Higher concentration, more particles per unit volume, higher frequency of efficient collisions.(aqueous solutions) Temperature Higher temperature, particles move faster with more energy, higher frequency of efficient collisions(all) Pressure Higher pressure, particles closer to one another, higher frequency of efficient collisions(gases) Surface Area Smaller particles, larger surface area, higher frequency of efficient collisions(solids) Endothermic Exothermic Catalyst Provides alternate pathway of lower activation energy, increases rate of reaction without being chemically changed(all)

Cation Table The observations with NaOH(aq) and NH3 (aq) are the same for Al3+ and Pb2+ ions Add Potassium Iodide (KI) to both solutions. A yellow precipitate (PbI2) is formed for Pb, while no precipitate formed for Al How to differentiate between Al and Pb

Salt Solution Light Blue pptWhite ppt Green ppt Red-brown ppt Al, Ca, Pb, Zn Cu Fe2+ Fe3+ Soluble Al, Pb, Zn Insoluble Ca Salt Solution Light Blue pptWhite ppt Green ppt Red-brown ppt Al, Pb, Zn Cu Fe2+ Fe3+ Soluble Zn Insoluble Al, Pb Deep Blue sol Cu No ppt NH4+ No ppt Ca2+ or NH4+ NaOH (aq) NH₃ (aq) Cation Table in excess in excess

Anion Table To remove carbonates and hydroxide ions! If dilute nitric acid is not added, precipitates of BaCO3 , Ag2CO3 and AgOH will form when barium nitrate / silver nitrate is added, which will interfere with the results. Sulfates, Chlorides and Iodides require Dilute Nitric Acids - Why?

Salt Solution NH3 Gas CO2 Gas White ppt White ppt CO32- NO3- SO42- Cl- No ppt I- Anion Table + HCl (aq) + NaOH (aq) and Al (s), heat + HNO3 (aq) and Ba(NO3)2 (aq) + HNO3 (aq) and AgNO3 (aq)

Gas Table