1. Displacement Reactions

2. + + Single Displacement Reactions
Single Displacement reaction: A chemical reaction in which an element takes the place of (displaces) another element in a compound
A + BC AC B (where A & B are metals)
A + BC BA C (where A & C are non-metals) + +

3. Displacing Metals With Metals
When a piece of copper is placed into silver nitrate, metallic silver ions form on the copper
The solution turns blue because copper atoms from the wire dissolve in solution and displaces the silver from the silver nitrate compound
Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s)

4. Displacing Metals With Metals
In this reaction a metal (copper) replaces another metal (silver)
Or, a positive ion (Cu2+) replaced another positive ion (Ag3+)
Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s)

5. The Activity Series
By trying different combinations of metals and compounds, scientists have arranged the metals according to their reactivity
The activity series is a list of elements ranked according to their chemical reactivity
Most reactive is at the top, least at the bottom
An element can only displace another if it is below it on the activity series!!

6. The Activity Series Hydrogen is the only non-metal in the series
Since hydrogen ions can be positively charged, metals can replace hydrogen in compounds
In these reactions, hydrogen gas H2(g) is formed
Metals above hydrogen can replace hydrogen from an acid, metals below hydrogen cannot
What do you get when you place Zn in HCl?

7. The Activity Series
An example of Zinc (Zn) displacing hydrogen gas from hydrochloric acid (HCl)
Zn(s) + 2HCl (aq) ZnCl2(aq) + H2(g)

8. Sample Problem: The Activity Series
Use the activity series to predict if the following reaction will occur. If not, indicate “NR” for “No Reaction”. If so, complete and balance the chemical equation
Al(s) + CuI2(aq)

9. Sample Problem: The Activity Series
Aluminum will replace copper
Aluminum becomes Al3+ and the bromide ion remains Br-
To be neutral, the new compound must be CuBr2
As a pure element Cu(s) has no charge
The skeleton equation is the same as the balanced equation
Al(s) + CuBr2(aq) Cu (s) + AlBr2 (aq)

10. Replacing Non-metals with Non-metals
The ion of a non-metal (Cl-) is negatively charged so it can only be replaced with another non-metal
F2(g) + 2NaI(s) I2(s) + 2NaF(s)

11. + + Double Displacement Reactions
Double Displacement reaction: A chemical reaction in which the positive ions of two compounds change places and form two new compounds
Double Displacement reactions often result in the product of an insoluble solid or precipitate
AB + CD AD CB (A & C are cations and B and D are anions) + +

12. Double Displacement Reactions
Example: when a yellow aqueous solution of potassium chromate is added to a colorless aqueous solution of silver nitrate a red precipitate of silver chromate is formed:
2AgNO3(aq) + K2CrO4(aq) Ag2CrO4(s) + 2KNO3(aq)

13. Double Displacement Reactions
Complete and balance the following double displacement reaction. You do not need to predict the states of the products
NaCl(aq) + AgNO3(aq)

14. Double Displacement Reactions
Solution:
NaCl(aq) + AgNO3(aq)
This is a double displacement reaction so the two cations must switch
Sodium and silver will therefore switch – both have a 1+ charge so the ratio to anions does not change
The skeleton equation is the same as the balanced equation for this reaction
NaCl(aq) + AgNO3(aq) AgCl NaNO3

15. Summary of Chemical Reactions
Reaction Type
Chemical Equation
Example
Characteristics
Synthesis
A + B AB
2H2(g) + O2(g)
2H2O(g)
Two reactants join forming a single compound
Decomposition
AB A + B
2C7H5N3O6(s )
3N2(g) H2O (g) + 7CO (g) + 7C(s)
A single compound breaks apart making two or more products
Single Displacement
A + BC AC + B
A + BC BA + C
2Al(s) + 3CuCl2(aq)
2AlCl3(aq) + 3Cu(s)
A reactive element takes the place of a less reactive element
Double Displacement
AB + CD AD + BC
NaCl(aq) + AgNO3(aq)
AgCl(s) + NaNO3(aq)
Two ionic compounds switch ions to form new compounds & a ppt