Types of Chemical Reactions Honors Chemistry Ch 8

Types of Reactions Classification of chemical reactions enables us to organize information and ultimately predict the results of similar reactions without having to carry them out experimentally. Being able to identify the type of reaction helps you predict the product(s)

Steps to Writing Reactions Some steps for doing reactions Identify the type of reaction Predict the product(s) using the type of reaction as a model Write the skeleton reaction and then balance it Don’t forget about the diatomic elements! (HOFBrINCl) For example, Oxygen is O 2 as an element. In a compound, it can’t be a diatomic element because it’s not an element anymore, it’s a compound!

1. Synthesis reactions Synthesis reactions occur when two substances (generally elements) combine and form a compound. (Sometimes these are called combination or addition reactions.) Examples: calcium + sulfur  calcium sulfide carbon dioxide + sodium oxide  sodium carbonate In other words: element + element  compound or Simple compound + simple compound  complex compound

Practice Predict the products. Write and balance the following synthesis reaction equations. Ex. 1: Sodium metal reacts with chlorine gas  Ex 2: phosphorus + oxygen  diphosphorus pentoxide

Synthesis Reactions Here is another example of a synthesis reaction

2. Decomposition Reactions Decomposition reactions occur when a compound breaks up into the elements or in a few to simpler compounds Examples: iron(III) sulfide  iron + sulfur Sodium hydrogen carbonate  sodium hydroxide + carbon dioxide In other words: compound  element + element or Complex compound  compound + compound

Let’s Practice Predict the products. Then, write and balance the following decomposition reaction equations: Ex. 3: copper(I) chloride  Ex 4: water 

Decomposition Reactions Another view of a decomposition reaction:

3. Single Replacement Reactions Single Replacement Reactions occur when one element replaces another in a compound. A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-) Examples: calcium oxide + magnesium  magnesium oxide + calcium calcium chloride + fluorine  calcium fluoride + chlorine In other words: element + compound  element + compound A + BC  AC + B (if A is a metal) OR A + BC  BA + C (if A is a nonmetal) (remember the cation always goes first!)

Single Replacement Reactions Another view:

Let’s Practice Write and balance the following single replacement reaction equation: Ex 5: aluminum + barium chloride  Ex 5: aluminum + barium chloride  Ex. 6: ammonium oxide + iodine  Ex. 6: ammonium oxide + iodine 

The Activity Series In order for an element to replace another, it must be more active. If this is not the case, then no reaction occurs. A. chromium + lead (II) chloride  B. zinc + potassium hydroxide  C. magnesium + sulfuric acid  D. iodine + sodium chloride  C. fluorine + sodium chloride 

4. Double Replacement Reactions Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound Example: silver nitrate + sodium chloride  sodium nitrate + silver chloride In other words : Ionic Cmpd + ionic cmpd  different cmpd+ different cmpd AB + CD  AD + CB

Double Replacement Reactions Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together Example: AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq) Another example: K 2 SO 4(aq) + Ba(NO 3 ) 2(aq)  KNO 3(aq) + BaSO 4(s) 2

Let’s Practice Predict the products. Balance the equation  Example 8: sodium chloride + aluminum oxide  Example 9: potassium permanganate + calcium phosphate 

There are three types of products that drive double replacement reactions 1. Formation of an insoluble or slightly soluble precipitate 1. Formation of an insoluble or slightly soluble precipitate 2. Formation of a gaseous product 2. Formation of a gaseous product 3. formation of a molecular compound-like water 3. formation of a molecular compound-like water

5. Combustion Reactions Combustion reactions occur when a hydrocarbon reacts with oxygen gas. This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”: 1) A Fuel (hydrocarbon) 2) Oxygen to burn it with 3) Something to ignite the reaction (spark)

Combustion Reactions In general: C x H y + O 2  CO 2 + H 2 O Products in combustion are ALWAYS carbon dioxide and water. (although incomplete burning does cause some by- products like carbon monoxide) Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C 8 H 18 )

Combustion Examples: methane + oxygen  carbon dioxide + water C 8 H 18 + O 2  CO 2 + H 2 O In other words: hydrocarbon + oxygen  carbon dioxide + water vapor

Let’s practice Write the products and balance the following combustion reaction: Example 10: C 6 H 6 + O 2  Example 11: C 2 H 5 OH + O 2 

Neutralization reaction In other words: acid + base  salt + water Ex 12: hydrochloric acid + sodium hydroxide  HCl + NaOH  NaCl + HOH Ex 13: potassium hydroxide + sulfuric acid  KOH +HCl  KCl +HOH

Net ionic precipitation reaction *** more to come on this*** In other words: aqueous ion + aqueous ion  solid precipitate Ex 14: aqueous silver ion + aqueous chloride  Ag +1 (aq) + Cl -1 (aq)  AgCl (s) Ex: 15: aqueous lead(II) ion + aqueous hydroxide  Pb +2 (aq) + 2OH -1 (aq)  Pb(OH) 2 (s)

Dissociation reaction In other words: solid soluble salt or base  component ions Ex 16: iron(III) chloride dissolves in water  FeCl 3 (s)  Fe +3 (aq) + 3 Cl -1 (aq) Ex 17: barium hydroxide dissolved in water  Ba(OH) 2 (s)  Ba +2 (aq) + 2 OH -1 (aq)

Ionization reaction In other words: acid + water  hydronium ion + anion Ex 18: hydrochloric acid reacts with water  HCl + H 2 O  H 3 O +1 (aq) + Cl -1 (aq) Ex 19: sulfuric acid reacts with water  H 2 SO 4 + H 2 O  H 3 O +1 (aq) + HSO 4 -1 (aq)