Single Replacement Reactions – Activity Series

Single replacement reactions are reactions that involve an element replacing one part of a compound. The products include the displaced element and a new compound. An element can only replace another element that is less active than itself. In other words, the elemental metal or nonmetal must be more active than the metal or nonmetal found in the compound for the reaction to occur.

General activity series for metals:

(most active) Li K Ca Na Mg Al Zn Fe Pb [H2] Cu Ag Pt Au (least active)

General activity series for nonmetals:

(most active) F2 Cl2 Br2 I2 (least active)

Examples of common single replacement reactions:

1. Active metals replace less active metals from their compounds in aqueous solution. Magnesium turnings are added to a solution of iron (III) chloride 3 Mg + 2 FeCl3  2 Fe + 3 MgCl2 because Mg is more active than Fe

2. Active metals replace hydrogen in water. Sodium is added to water 2 Na + 2 HOH  H2 + 2 NaOH because Na is more active than H2

3. Active metals replace hydrogen in acids. Lithium is added to hydrochloric acid 2 Li + 2 HCl  H2 + 2 LiCl because Li is more active than H2

4. Active nonmetals replace less active nonmetals from their compounds in aqueous solution. Chlorine gas is bubbled into a solution of potassium iodide. Cl2 + 2 KI  I2 + 2 KCl because Cl2 is more active than I2

Nonexamples of reactions that will not take place because a less reactive element is combined with a more reactive element in compound form.

5. Chlorine gas is bubbled into a solution of potassium fluoride.

Cl2 + KF  no reaction because Cl is less active than F

6. Zinc is added to a solution of sodium chloride.

Zn + NaCl  no reaction because Zn is less active than Na

Practice Problems: Use the activity series above to predict and balance the following single replacement reactions. Use abbreviations to indicate the appropriate phase of reactants and products where possible. Not all of the reactions will occur. For those that do not occur, write “no reaction” as the product.

1. copper metal + water 

2. aluminum foil + silver nitrate solution 

3. platinum ring + iron (III) chloride solution 

4. magnesium metal + lead (II) nitrate solution 

5. iodine crystals + salt water 

6. potassium metal + zinc chloride solution 

7. chlorine gas + aqueous hydrofluoric acid 

8. iron metal + sodium phosphate solution 

9. liquid bromine + magnesium chloride solution 

10. iron metal + copper sulfate solution 