Exothermic vs. Endothermic

Decomposition of Nitrogen Triiodide 2 NI 3 (s) N 2 (g) + 3 I 2 (g) NI 3 I2I2 N2N2

Exothermic Reaction Reactants  Products + Energy 10 energy = 8 energy + 2 energy Reactants Products -H-H Energy Energy of reactants Energy of products Reaction Progress

Endothermic Reaction Energy + Reactants  Products +  H Endothermic Reaction progress Energy Reactants Products Activation Energy

Effect of Catalyst on Reaction Rate reactants products Energy activation energy for catalyzed reaction Reaction Progress No catalyst Catalyst lowers the activation energy for the reaction. What is a catalyst? What does it do during a chemical reaction?

An Energy Diagram activation energy EaEa reactants products course of reaction energy Animation by Raymond Chang All rights reserved

Formation of a solid AgCl AgNO 3 (aq) + KCl(aq)  KNO 3 (aq) + AgCl(s)

Single and Double Replacement Reactions Double-replacement reaction CaCO HCl  CaCl 2 + H 2 CO 3 General form: AB + CD  AD + CB Single-replacement reaction Mg + CuSO 4  MgSO 4 + Cu General form: A + BC  AC + B

Single displacement is a type of a reaction when a metal reacts with a compound containing a metal, where the single metal in the reaction is more reactive replaces the less reactive metal in the compound. Single-replacement reaction Mg + CuSO 4  MgSO 4 + Cu General form: A + BC  AC + B

DOUBLE DISPLACEMENT REACTIONS: In a double displacement reaction (ionic reaction) the ions of two compounds exchange places in an aqueous solution to form two new compounds. Double-replacement reaction CaCO HCl  CaCl 2 + H 2 CO 3 General form: AB + CD  AD + CB

Double Replacement Reaction

Synthesis Reactions - when two compounds or elements combine to make one molecule or compound. A+ B --> AB 2 H 2 + O > 2 H 2 O Decomposition Reactions - a compound or molecule breaks down into simpler elements or compounds AB - -> A + B CO > C + O 2

Important Chemical Reactions Oxidation Reactions Reactant + Oxygen > Products Oxidation reactions are fundamental to our existence Definition: A chemical change involving oxygen Oxidation reactions can occur more rapidly in the presence of humidity in the air, or in the presence of light GALVINIZATION – coating iron materials with zinc to prevent the formation of rust.

Combustion Combustion – Form of oxidation that releases a large amount of energy (HIGHLY EXOTHERMIC). Three requirements for a combustion: Fuel – reacts with oxidizing agent to release energy Oxidizing agent – substance that causes a fuel to react (usually oxygen) Ignition temperature – the required temperature needed to combust the fuel Three types of combustions: Rapid – Release a lot of energy in a short period of time Spontaneous – Fuel ignites without the need for outside energy Slow – Occurs of long period of time

A Combustion reaction usually looks like: Fuel + oxygen > CO 2 + H 2 O + Energy CH 4 + O > CO 2 + H 2 O

Other important Chemical Reactions... Cellular Respiration Glucose + Oxygen -----> Carbon Dioxide + Water + Energy Photosynthesis Light + Carbon Dioxide + Water-----> Oxygen + Glucose