chemical reaction types

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1 Single replacement and Double replacement r. Shields Regents Chemistry L11 L06

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Chemical Reaction Types. Single replacement and Double replacement. Mr. ShieldsRegents Chemistry L11 L06. Combustion. Reaction Types. A+BC AB+C. AX+BY AY+BX. We’ve discussed Synthesis, Decomposition and Combustion. Let’s now look at Single and Double Replacement reactions. +. - PowerPoint PPT Presentation

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Page 1: Chemical Reaction Types

1

Single replacement and Double replacement

Mr. Shields Regents Chemistry L11 L06

Page 2: Chemical Reaction Types

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Reaction TypesReaction Types

A+BCAB+CAX+BYAY+BX

Combustion

We’ve discussed Synthesis, Decomposition and Combustion.Let’s now look at Single and Double Replacement reactions.

Page 3: Chemical Reaction Types

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Single ReplacementSingle Replacement

In a single replacement reaction an UNCOMBINED Element replaces one of the elements in a compound.

A+BCAB+C

+

A + B---C B----A + C

A replaces C and C becomes the uncombined element

uncombined uncombined

+

Page 4: Chemical Reaction Types

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Single ReplacementSingle Replacement

Typically the compounds involved in single replacement Reactions are ionic and occur in solution. For example…

Cl2 + 2NaBr (aq) 2NaCl (aq) + Br2

+ +

Example:

Page 5: Chemical Reaction Types

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Single ReplacementSingle Replacement

The reaction of Chlorine to replace Bromine is an exampleOf a NON-METAL REPLACING A NON-METAL

Cl2 + 2NaBr (aq) 2NaCl (aq) + Br2

There are also single replacement reactions in which aMETAL REPLACES ANOTHER METAL.

2AgNO3 (aq) + Cu Cu(NO3)2 (aq) + 2Ag

-In single replacement reactions:- Metals will only replace metals- Non-metals will only replace non-metals

Page 6: Chemical Reaction Types

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Single ReplacementSingle Replacement

2AgNO3 (aq) + Cu (s) Cu(NO3)2 (aq) + 2Ag (s)

Let’s look at what’s happening in this reaction…

ClearAgNO3

sol’n &Solid CuWire

BlueCu(NO3)2

Sol’n &Solid Ag

The silver in this reaction “precipitates” out of the solution

Page 7: Chemical Reaction Types

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Single ReplacementSingle Replacement

In single replacement reactions:

- Metals replace metals

- Halogen Non-metals replace halogen non-metals

F2 Cl2 Br2 I2

K Al Fe Cu

Page 8: Chemical Reaction Types

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We saw Copper can replace Ag but there are otherMetals that will replace metals as well. For exampleZinc will replace Cu in ionic compounds.

Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu (s)

Cu wire isIn an aqueousSolution of AgNO3

Zn & Cu

Cu & Ag

Page 9: Chemical Reaction Types

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Activity SeriesActivity Series

We know certain metals will replace other metalsAnd certain Non-metals will replace other non-metals.

But how can we determine which will replace which?

To make this determination you need to refer to

TABLE J

in your reference tables.

TABLE J IS KNOWN AS THE ACTIVITY SERIES

Page 10: Chemical Reaction Types

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In the activity series the element higher on the list willReplace from a compound any element lower on the list.

For example: Al (s) + Cr(NO3)3 (aq) Al(NO3)3 (aq) + Cr (s)

or 3Cl2 (g) + 2AlI3 (aq) 2AlCl3 (aq) + 3I2 (s)

More reactive

Less Reactive

Page 11: Chemical Reaction Types

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The activity series also lists Hydrogen with the metals. AnyMetal higher on the list than hydrogen will replace it fromEither water or acid.

2K + 2H20 2KOH + H2

Ni + 2HCl NiCl2 + H2

If the uncombined metal is below the combined metal(or hydrogen) it will not replace it from the compoundand the reaction will NOT OCCUR !!

Replacing hydrogen from water is more difficult than Replacing hydrogen from acids. But, those metals higher Up the activity series will react with water more easily.

Page 12: Chemical Reaction Types

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Try theseTry theseWill these reactions proceed as indicated?

1)3Mg + 2Fe(NO3)3 3Mg(NO3)2 + 2Fe

2)Pb + Co(NO3)2 Pb(NO3)2 + Co

3)Br2 + 2KCl 2KBr + CL2

4)2Au + 6HCl 2AuCl3 + 3H2

5) Zn + 2HNO3 Zn(NO3)2 + H2

Yes

No

No

No

Yes

Notice in all these reactions a new compound and a freeElement are formed

Page 13: Chemical Reaction Types

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Double Replacement ReactionsDouble Replacement Reactions

As with single replacement reactions Double replacementReactions take place with ionic compounds in solution.

In this case however, both reactants are compounds.

For example …

H replaces Na

Na replaces H

Page 14: Chemical Reaction Types

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Double Replacement ReactionsDouble Replacement ReactionsThese reactions occur in solution because the ions of thecompounds must be able to move freely from one place toanother

H+ + NO3- + 2Na+ + CO3

-2 2H+ + CO3-2 + Na+ + NO3

-

This equation is known as a COMPLETE IONIC EQUATION

Since these compounds are all in sol’n we can write theequation a little differently showing all the ions present:

Page 15: Chemical Reaction Types

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Double Replacement ReactionsDouble Replacement ReactionsMaybe you’re wondering “if this reaction can occur as Indicated in solution why can’t the reverse reactionHappen just as easily?”

2H+ + CO3-2 + Na+ + NO3

- H+ + NO3- + 2Na+ + CO3

-

2

In other words …

Well it can! So in order for these reactions to proceed Forward to completion something else must occur

Page 16: Chemical Reaction Types

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Double Replacement

“A molecule forms”

The criteria necessary to drive double replacement reactionsForward to completion will be one of the following:

We’ll discuss thisOne in a later unit

Reaction Start Reaction Complete

Page 17: Chemical Reaction Types

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1- Precipitate forms1- Precipitate formsSome compounds are INSOLUABLE in water. Therefore,In double replacement reactions the IONS of these Insoluble compounds are noLonger free and therefore canNot react with other free ions

For example:

Ba(NO3)2 (aq) + CuSO4 (aq) Cu(NO3)2 (aq) + BaSO4 (s)

These insoluble compounds that areFormed are known as PRECIPITATES

A common precipitate

Page 18: Chemical Reaction Types

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Another example of a common precipitate that forms in This kind of reactions is AgCl

A white precipitate

Ions in the Complete Ionic Equation that are not involvedIn forcing the double replacement reaction to completionAre known as SPECTATOR IONS. For example, the aboveEquation can be rewritten as a NET IONIC EQUATION …

Ag+ + Cl- AgCl (s)

Double Replacement

The only ionsInvolved in Driving the reaction to completion

Page 19: Chemical Reaction Types

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Gas EvolutionGas EvolutionThe other type of double replacement reaction that goes To completion is one in which a gas is evolved.

For example …

H2CO3 H20 + CO2 (g)

Carbonic acid is theAcid that gives soda itsfizz

Once the gas is evolved, the ions from which its generatedAre no longer available. The rxn is driven to completion

Decomposes

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Molecule formationMolecule formation

The last process we’ll discuss that drives doublereplacement reactions to completion are reactions thatLead to the formation of molecules (i.e. covalently bonded Compounds like water)

Molecules can not ionize and thus once formed they areNo longer available for replacement reactions.

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Molecule formationMolecule formation

The most common example of molecule formation is ACID-BASE neutralization. In this type of double replacementReaction WATER is the molecular compound that’s formed

For example:HCl + KOH KCl + H2O

Complete ionic equation:H+ + Cl- + K+ + OH- K+ + Cl- + H2O

Net Ionic equation:H+ + OH- H2O (the general equation for acid-base neutralizations)

Acid Base A Salt Water

A “Molecule”

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Try theseTry theseName the reaction type:

CaCO3 CaO + CO2

CH4 + O2 CO2 + H20

Mg + ZnCl2 MgCl2 + Zn

MgSO4 (aq) + Ba(NO3)2 (aq) BaSO4 (s) + Mg(NO3)2 (aq)

Mg + H2SO4 MgSO4 + H2 (g)

HCL + Ca(OH)2 CaCl2 + H20

Decomp

Combustion

Single Rep.

Double Rep.Single Rep.

Double Rep.

CO2 + H2O H2CO3 Synthesis