Chapter 8 Chemical Equations and Reactions

Section 1

Describing Chemical Reactions Word equation: a chemical reaction written out in words Skeletal equation: a chemical equation that does not show the relative amounts of reactants and products

Describing Chemical Reactions Symbols used in chemical equations State symbols (common element phases)

Describing Chemical Reactions Heat is added Catalyst is used Specific conditions A solid is produced A gas is produced

Describing Chemical Reactions Change word equation into skeletal equation 1)Nitrogen gas is added to hydrogen gas to produce ammonia gas. 2)Oxygen gas and liquid water are produced when hydrogen peroxide is decomposed using manganese (IV) oxide as a catalyst.

Describing Chemical Reactions Signs of a chemical reaction 1)Change in color 2)Change in odor 3)Production of new solid 4)Production of new gas 5)Evolution of energy as light or heat

Balancing Chemical Equations Placing coefficients in order to balance the atoms on both side of equation law of conservation of mass

Describing Chemical Reactions A chemical change or chemical reaction is represented by a chemical equation Reactants: chemicals that go into a reaction Products: chemicals that are produced from a reaction Reactants  Products

Balancing Chemical Equations Hints for balancing: 1)Balance atoms that only appear once, first 2)If possible, keep polyatomic ions together 3)Balance H and O last 4)Stay calm

Balancing Chemical Equations Write word and balanced formula equation: solid sodium oxide is added to water at room temperature and forms sodium hydroxide (dissolved in the water).

Balancing Chemical Equations Aqueous solutions of barium chloride and sodium chromate react to produce a precipitate of barium chromate plus sodium chloride in aqueous solution.

Balancing Chemical Equations Pb(NO 3 ) 2 + HCl → PbCl 2 + HNO 3 Na + H 2 O → NaOH + H 2 Sb 2 S 3 + HCl → H 3 SbCl 6 + H 2 SSb 2 S 3 + HCl → H 3 SbCl 6 + H 2 S

Section 2

Types of Chemical Reactions 1)Synthesis 2)Decomposition 3)Single Replacement 4)Double Replacement 5)Combustion

Types of Chemical Reactions Synthesis Reaction: two or more substances combine to form a new compound. This type of reaction is represented by the following general equation.

Things to Remember When Writing rxns Oxidation numbers for ionic cpds Formulas for:diatoms, polyatomics, monatomics. Nomenclature-prefixes (nonmetals), roman numerals(transition metals and metals with more than 1 charge). Start with the metal. State facts Balance

Types of Chemical Reactions Synthesis reactions of metals with oxygen, sulfur, and halogens

Synthesis Rxns Metals w/Sulfur

Synthesis Rxns w/Halogens Most metals react w/ gp 17 elements. Gp 1 elements react with metals to form ionic compounds w/formula MX (M=metal, X=halogen) Gp 2 elements react w/halogens to form ionic cpds w/formula MX

Halogens undergo synthesis rxns w/ many different types of metals. F is so reactive it combines w/ almost all metals.

Types of Chemical Reactions Synthesis of metal oxides with water Synthesis of nonmetal oxides with water

Certain metal oxides and nonmetal oxides react with each other in synthesis reactions to form salts.

Types of Chemical Reactions Decomposition Reaction: a single compound undergoes a reaction that produces two or more simpler substances. This type of reaction is represented by the following general equation.

Types of Chemical Reactions Decomposition reaction are too difficult to discuss specific reactions

Synthesis Rxn Practice 2 or more reactants come together to form 1 cpd. A+B- AB Complete the following word equation and write and balance the formula equation.

Types of Chemical Reactions Single Replacement Reaction: one element replaces a similar element in a compound This type of reaction is represented by the following general equation.

Types of Chemical Reactions Not all single replacement reactions will take place. “A” has to be more reactive than “B” or “X” has be to more reaction than “Y” The ability of an element to react is referred to as the element’s activity.

Types of Chemical Reactions An activity series is a list of elements organized according to the ease with which the elements undergo certain chemical reactions. The most-active element is placed at the top in the series. It can replace each of the elements below it from a compound in a single- displacement reaction. Activity series are used to help predict whether certain chemical reactions will occur.

Types of Chemical Reactions Double Replacement Reaction: the ions of two compounds exchange places in an aqueous solution to form two new compounds This type of reaction is represented by the following general equation.

Types of Chemical Reactions Combustion Reaction: a substance combines with oxygen, releasing a large amount of energy in the form of light and heat This type of reaction is represented by the following general equation.

combustion rxn balancing CH 3 OH + O 2  CO 2 + H 2 O C 6 H 14 + O 2  CO 2 + H 2 O Combustion of dicarbon hexahydride Solid carbon reacts with oxygen gas to produce carbon dioxide gas

1) NaOH + KNO 3 --> NaNO 3 + KOH 2) CH O 2 --> CO H 2 O 3) 2 Fe + 6 NaBr --> 2 FeBr Na 4) CaSO 4 + Mg(OH) 2 --> Ca(OH) 2 + MgSO 4 5) NH 4 OH + HBr --> H 2 O + NH 4 Br 6) Pb + O 2 --> PbO 2 7) Na 2 CO 3 --> Na 2 O + CO 2

Predicting Products

Predicting products of synthesis 1)O 2 + Al  2)K + S  3)Ca + F 2  4)H 2 + O 2 

Predicting products of single replacement TRemember to use activity series! T 1)K+AgCl  2)F 2 +AgCl  3)Ca+NaOH  4)Li+H 2 O  5)barium chloride + bromine 6)hydrogen chloride + zinc

Predicting products of double replacement 1)BeI 2 + Cu 2 SO 4  2)Ni(NO 3 ) 3 + KBr  3)cobalt(III) bromide + potassium sulfide  4)barium nitrate + ammonium phosphate 

Molecular equation: chemical formulas Complete ionic equation: soluble compounds are written as ionic components Net ionic equation: ionic equation showing only ions responsible for ppt Spectator ions: ions not involved in formation of ppt

AgNO 3 (aq) + KCl (aq)  AgCl (s) + KNO 3 (aq)

manganese(II) chloride (aq) + ammonium carbonate (aq)  manganese(II) carbonate (s) + ammonium chloride (aq)

chromium(III) nitrate (aq) + iron(II) sulfate (aq)  chromium(III) sulfate (aq) + iron(II) nitrate (aq)

Cu(NO 3 ) 2 + NaOH  Li + CaCl 2  Pb(NO 3 ) 2 (aq) + K 2 SO 4 (aq) 

Copper (II) bromide + aluminum chloride  Calcium acetate + sodium chloride  Zinc + calcium chloride 