Chem Study Guide

Christina Alcorta, Dymond Elliott
Klawender 2-4
May 22, 2012
Chapter 8 Chemical Equations and Reactions
Quick Review
8.1 Describing Chemical Reactions
* In a chemical reaction atoms rearrange to form new substances.
* A chemical analysis is the only way to prove that a reaction has occurred.
* symbols are used in chemical equations to identify the physical states of a substanceand the physical conditions during a chemical reaction [(s),(l),(g),(aq),→,⇄]
8.2 Balancing Chemical Equations
* A word equation is translated into a formula equation to describe the change of reactants into products.
* The masses, numbers, and types are going to be the same on both sides of the balanced equation
* Coefficients in front of the formulas of reactants and products areused to balance an equation. Remember: subscripts CANNOT be changed.
8.3 Classifying Chemical Reactions
* See 8.3 Terms
8.4 Writing Net Ionic Equations
* A total ionic equation shows all aqueous ions for a reaction
* Spectator ions do not change during a reaction and can be removed from the total ionic equation
* Net ionic equations show only the net change of a reaction and are thebest way to describe displacement and double displacement reactions.
Terms
8.1
Chemical reaction- The process by which one or more substances change to produce one or more different substances
Chemical Equation- A representation of a chemical reaction that uses symbols to show the relationship between the reactants and the products.
8.2
Coefficient- A small whole number that appears as afactor in front of a formula in a chemical equation.
8.3
Combustion reaction- a reaction of a carbon-based compound with oxygen
Synthesis reaction- a reaction in which two or more elements or compounds may combine to form a more complex compound.
Decomposition reaction- a reaction in which a single compound breaks down to form two or more simpler substances
Activity series- a series of elementsthat have similar properties and that are arranged in descending order of chemical activity
Double-displacement reaction- a reaction in which a gas, a solid precipitate, or a molecular compound forms from the apparent exchange of atoms or ions between two compounds
8.4
Spectator ions- ions that are present in a solution in which a reaction is taking place but that do not participate in thereaction

8.1 Describing Chemical Reactions
Chemical Change
* the original substance are reactants and the substance created are products
* Evidence of Chemical Change
* release of heat → formation of gas
* release of energy as light → formation of precipitate (an insoluble solid)
* Production of sound → Change in color
* Reduction or increase of temperature →Change in odor
* absorption or release of electrical energy
* all changes of state are physical changes ( evaporation, condensation, melting, and freezing)
* chemical reactions release or absorb energy
* methane + oxygen → carbon dioxide + water + energy
* Molecules and atoms of the reactants must come into contact with each other for a reaction to take place.
Equationand Reaction Information
* An equation is balanced so it obeys the law of conservation of mass
* Equations can show physical states and reaction conditions through symbols
* (s), (l), (g)- solid, liquid, or gaseous state
* (aq)- substance in an aqueous solution (dissolved in water)
* → - yields/ produces
* ⇆ - a reversible reaction, products can reform intoreactants
* delta- reactants are heated
* pd- catalyst is used to speed up reaction

8.2 Balancing Chemical Equations
Reactions Conserve Mass
* Law of conservation of mass- in ordinary physical and chemical changes, mass is neither created nor destroyed.
* products and reactants are made up of the number and kinds of atoms, but they rearranged and connected differently.
*...