Single Replacement Reactions

"Can I Cut In?"

In a single replacement reaction, one element replaces another element in a compound.  Metals always replace metals;  nonmetals always replace nonmetals.

Element + Compound --->  Element + Compound

An activity series is needed when predicting products of reactions because only more active elements can replace less active elements.  The most active elements are at the top of the Activity Series Chart.

Examples:

1.  Which of the following elements in each pair is most active?

• zinc or copper?

• gold or iron?

• calcium or nickel?

• flourine or chlorine?

• iodine or fluorine?

Answers:  The elements that are highlighted in blue are most active because they are highest up on the activity series!  They are most likely to react to form a compound!

2.  Au_(s) + KNO_3(aq) --->  ???

First, identify the reaction as a single replacement reaction. Element + Compound

Write out the names of the reactants: Gold + Potassium Nitrate

Look on the activity series to check the position of gold (Au) and potassium (K). 

• Gold is lower than potassium on the Activity Series.  Therefore, gold cannot take the place of potassium in a compound. Gold will not react with potassium nitrate solution!

If the reaction does not occur, write:

 Au_(s) + KNO_3(aq) --->  NO REACTION

3.  Zn_(s) + AgNO_3(aq) --->  ???

First, identify the reaction as a single replacement reaction. Element + Compound

Write out the names of the reactants: Zinc + Silver Nitrate

Look on the activity series to check the position of zinc (Zn) and silver (Ag). 

• Zinc is higher than silver on the Activity Series.  Therefore, zinc can take the place of silver in a compound. Zinc will react with silver nitrate solution!

If the reaction does occur, write the equation in words:

 Zinc + Silver Nitrate ---> Silver + Zinc Nitrate

• Use the periodic table and ion chart to write correct formulas for each of the formulas above.

• _{Add coefficients to balance the equation.}

Zn + 2AgNO₃  --->  2Ag + Zn(NO₃)₂

3.