CHEMICAL REACTIONS

Performance Objectives Identify the types of chemical reactions Complete, write, balance chemical equations Calculate mass-mass (stoichiometry/limiting and excess) problems for chemical reactions Calculate percent yield in a chemical reaction

CHEMICAL EQUATIONS Show reactants and products The Law of Conservation of Mass coefficients symbols

CHEMICAL REACTION Process by which one or more substances are changed into one or more different substances. Represented by a chemical equation

Characteristics of Chemical Reactions Always produces a new substance Always results in a change of energy –heat, light

CAPACITY TO REACT Determined by an elements valance electrons

BALANCING EQUATIONS PRACTICE PROBLEMS HANDOUTS

TYPES OF CHEMICAL REACTIONS Synthesis Decomposition Single displacement/replacement Double displacement/replacement Combustion

THREE TYPES OF DECOMPOSITION ( memorize) Metal chlorate  metal chloride + O 2 metal carbonate  metal oxide + CO 2 metal hydroxide  metal oxide + H 2 O

COMPLETING CHEMICAL REACTIONS PRACTICE AND HANDOUTS

STOICHIOMETRY Used to determine the masses of materials involved in chemical reactions also called mass-mass relationships

Sample problems How many grams of silver chloride can be produced from the reaction of 17.0 grams of silver nitrate with excess sodium chloride solution? How many grams of copper (I) sulfide can be produced from 9.90 grams of copper(I) chloride reacting with an excess of hydrogen sulfide gas?

PERCENTAGE YIELD Comparison of actual mass to theoretical mass theoretical mass determined by stoichiometry calculations Formula

Sample problem 6.2 grams of calcium hydroxide decomposes. –How much water is produced? –What is the percent yield if ½ grams of water is produced? –What is the percent error?

Limiting Reactants Limiting reactants –the reactant that is completely consumed in the reaction excess reactants –the reactant in which some is left over after the reaction is completed. The amount of the product produced is determined by the limiting reactant

LIMITING REACTANTS Aluminum sulfide can form from a reaction of 9.0 grams of aluminum with 8.0 grams of sulfur.

Identify the excess compound. Identify the limiting compound. Determine the number of grams that remains in excess after the reaction. Determine the number of grams of aluminum sulfide produced.

Activity Series of the Elements activity – ability of an element to react Activity series – –List of elements organized according to the ease with which the elements undergo certain chemical reactions –Determined by single displacement reactions

Using an activity series Series is used as a general guide handout Elements near the top are most reactive –Can replace elements below them but not above

INDICATORS OF A CHEMICAL REACION Production of heat or light Production of a gas Formation of a precipitate –A solid that is produced as a result of a chemical reaction in solution and that separates from the solution Color change