5.2 Displacement Reactions

Learning Goals• Learn how to read and use the activity series

• Learn what is a single displacement reaction and how to create a single displacement reactions

• Learn what is a double displacement reaction and how to create a double displacement reaction

Classifying Chemical Reactions• The new substances, or products, that form during chemical changes

will depend on the type of chemical reaction occurring.

• There are four main types of chemical reactions:

1) Synthesis Reactions

2) Decomposition Reactions

3) Single Displacement Reactions

4) Double Displacement Reactions

Single Displacement ReactionsIn a single displacement reaction, one element takes the place of (displaces) another element in a compound.

There are two general forms of equations for a single displacement reaction:

For a single displacement, where A is a metal:

For a single displacement, where A is a non-metal:

Example 1A single displacement reaction involving a metal replacing another metal occurs when copper is placed in an aqueous solution of silver nitrate.

copper + silver nitrate copper(II) nitrate + silver

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

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

Metals differ in their reactivity. The activity series is a list of metals organized according to their chemical reactivity; the most reactive metal appears at the top and the least reactive metal appears at the bottom.

A reactive metal will displace or replace a metal in a compound that is below it in the activity series.

Looking back at the previous example:

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

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

Could it be the other way around?

No reaction

Example 2A single displacement reaction involving a metal replacing hydrogen occurs when zinc is placed in an aqueous solution of hydrochloric acid (hydrogen chloride).

zinc + hydrochloric acid zinc chloride + hydrogen

ZnCl2(aq) + H2(g)Zn(s) + HCl(aq)

Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

A single displacement reaction involving a non-metal replacing another non-metal occurs when fluorine is placed in an aqueous solution of potassium iodide.

fluorine + potassium iodide potassium fluoride + iodine

KF(aq) + I2(g)F2(g) + KI(aq)

F2(g) + 2KI(aq) 2KF(aq) + I2(g)

Example 3

Double Displacement ReactionsIn a double displacement reaction, the cations of two different compounds exchange places, forming two new compounds.

The general form of the equation is:

In this equation, A and C are cations and B and D are anions.

ExampleAn example of a double displacement reaction occurs when barium hydroxide and sodium sulfate are mixed in a solution.

barium hydroxide + sodium sulfate barium sulfate + sodium chloride

BaSO4(s) + NaOH(aq)Ba(OH)2(aq) + Na2SO4(aq)

Ba(OH)2(aq) + Na2SO4(aq) BaSO4(s) + 2NaOH(aq)

ExampleThe following is a double displacement reaction.

Complete and balance the chemical equation.

AlCl3(aq) + CuNO3(aq)

Homework

Textbook: • Read Section 5.2• Questions pg 193 # 1, pg 196 # 1

Formal Lab Report Due Thursday!