Classifying Reaction

Objectives

• Identify, define, and explain: combination reaction, synthesis reaction, decomposition reaction, single replacement reaction, double replacement reaction, combustion reaction, and rapid oxidation.

• Explain the importance of classifying reactions.

• Identify and classify a reaction as synthesis, decomposition, single replacement, double replacement, or combustion.

Initial Questions

• What are things you have previously classified?

• How have you classified those items?

• Why have you classified those items?

Classifying reactions

• It is useful to classify chemical reactions because . . .

• There are FIVE basic types of reactions that we will need to be able to classify.

Synthesis Reactions

• A synthesis reaction is one in which a product is being created (or synthesized) from two or more elements. It is also a reaction where a more complex compound is created from two or more simpler complexes. There are always two or more reactants but only one product. Synthesis reactions are also known as composition reactions or combination reactions.

Synthesis Examples

• calcium + sulfur -->

• carbon dioxide + sodium oxide -->

Synthesis Examples

• calcium + sulfur --> calcium sulfide

• Carbon dioxide + sodium oxide --> sodium carbonate

• In other words:• element + element --> compound• Or: simple compound + simple

compound --> complex compound

Decomposition Reaction

• A decomposition reaction is one in which the single reactant is broken down into two or more elements or simpler compounds. It is the reverse of a synthesis reaction. It has only one reactant but two or more products. In such a reaction, the single reactant is decomposed into its constituent parts.

Decomposition Examples

• sodium hydrogen carbonate -->

• magnesium oxide -->

Decomposition Examples• sodium hydrogen carbonate -->

sodium hydroxide + carbon dioxide

• magnesium oxide --> magnesium + oxygen

• In other words:• compound --> element + element

• Or: Complex compound --> simple compound + simple compound (Or: Simple compound + element)

Single Replacement (SR)

• A single replacement reaction is one in which an element that is a reactant replaces an element in the other reactant. In other words, one partner is switched.

• Key point: a resulting ionic compound must have a + and a – ion. The switch cannot result in two positive ions or two negative ions forming a compound.

SR Examples

• calcium oxide + magnesium -->

SR Examples• calcium oxide + magnesium -->

magnesium oxide + calcium•• In other words:• element + compound --> different

element + compound

Double Displacement (DR)

• A double replacement reaction (also known as a double displacement reaction or metathesis reaction) is one in which the positive ions of the two reactants switch places. As products, each ion has a new and different partner that it originally had.

DR Examples

• silver nitrate + sodium chloride -->

DR Examples

• silver nitrate + sodium chloride --> silver chloride + sodium nitrate

• In other words:• compound + compound --> different

compound + different compound • (everything swaps and ends up with a

new partner)

What drives DR?

• There are 3 types of products that drive double replacements reactions.

• They are:

What drives DR?• There are 3 types of products that drive double

replacements reactions. • They are:

• the formation of an insoluble or slightly soluble precipitate

• Na2S + Cd(NO3)2 --> CdS(s) + 2 NaNO3

• the formation of a gaseous product• 2NaCN + H2SO4 --> 2HCN(g) + Na2SO4

• the formation of a molecular cmpd (eg. H2O)• Ca(OH)2 + 2 HCl --> CaCl2 + 2 H2O(l)

Combustion• A combustion reaction is a rapid oxidation that

usually produced a flame. For our purposes (but not always), oxygen (from the air) is a reactant. Hydrocarbons are compounds that contain hydrogen and carbon. (Combustion reactions may also include hydrocarbons that also contain oxygen.)

• When hydrocarbons combust (react with oxygen), the products are always carbon dioxide and water vapor.

Combustion Examples

• methane + oxygen -->

• Octane + oxygen -->

• C8H18 + O2 -->

Combustion Examples• methane + oxygen --> carbon dioxide

+ water vapor• Octane + oxygen --> carbon dioxide +

water vapor• C8H18 + O2 --> CO2 + H2O

• In other words: hydrocarbon + oxygen --> carbon dioxide + water vapor

Classifying Reaction

Acids & Bases & Reactions

• Give a good starting point for these questions . . .

• What’s an acid?

• What’s a base?

Neutralization Reaction

• NEUTRALIZATION REACTION: The reaction of an acid with a base producing a salt and water.

Neutralization Examples

• hydrochloric acid + sodium hydroxide -->

• potassium hydroxide + sulfuric acid -->

Neutralization Examples

• HCl + NaOH --> NaCl + HOH

• 2 KOH + H2SO4 --> K2SO4 + 2 HOH

• In other words:• Acid + Base --> Salt + Water

• Are these any different to balance and determine products than other reactions?

Dissociation Reaction

• DISSOCIATION REACTION: The reaction shows the separation of a soluble ionic salt or a base into its component ions in an aqueous reaction. You must include charge and the symbols to include the state of each species.

Dissociation Examples

• solid iron(III) chloride dissociates

• solid barium hydroxide dissociates

Dissociation Examples

• FeCl3(S) --> Fe3+(aq) + 3 Cl-(aq)

• Ba(OH)2(S) --> Ba2+(aq) + 2 OH-

(aq)

• In other words:

• Solid soluble salt or base --> component ions

Net Ionic Equations• NET IONIC PPT REACTION: The

reaction producing a solid precipitate (usually) from an aqueous reaction of two salts. The net ionic precipitation shows only those species that actually react. Any species that remains soluble (dissolved in water) are not included in this reaction. You must include the charge and the state of each species; check that the charge balances.

Net Ionic Examples

• silver ion and chloride ion form a precipitate

• lead(II) ion and hydroxide ion form a precipitate

Net Ionic Examples

• Ag+(aq) + Cl-(aq) --> AgCl(s)

• Pb2+(aq) + 2 OH-

(aq) --> Pb(OH)2 (S)

• In other words:

• aqueous ion + aqueous ion --> solid precipitate

Ionization Reactions

• IONIZATION REACTION: The reaction shows the reaction of an acid in water. The acid and water are the reactants and the products include the hydronium ion and the anion of the acid. You should include the charge and the state of each species.

Ionization Examples

• hydrochloric acid mixes with water

• sulfuric acid mixes with water

Ionization Examples

• HCl + H2O --> H3O+(aq) + Cl-(aq)

• H2SO4 + H2O --> H3O+(aq) +

HSO4(aq)

• In other words:

• Acid + water --> hydronium ion + anion

Activity Series

• In a single replacement reaction, a more active species replaces a less active species (but never the other way around).

• Let’s look at the activity series . . .

So, what happens here?

Do the following occur?

• A. chromium + lead (II) chloride

• B. zinc + potassium hydroxide

• C. magnesium + sulfuric acid

• D. iodine + sodium chloride

• E. fluorine + sodium chloride

Final Questions

• Classify and guess the products

• tin(II)oxide -->

• silver nitrate + sodium chloride -->

• sodium + water -->

• sodium + fluorine -->

More Final Questions

• Classify and guess the products:

• iron + oxygen --?

• Since this is combining with oxygen, can it be classified as a combustion reaction?

• Why or why not?