A single replacement occurs when an element becomes an ion in an ionic compounds (often cpd is aqueous so it is in ion form) and an ion in an ionic compound goes into its elementary form. These types of equations are redox reactions, because there are changes in the charge of the elements. They are in the form:
Examples:
Ca(s) + Mg(NO3)2 (aq) -> Mg(s) + Ca(NO3)2 (aq)
2 Al(s) + 3 Zn(SO4)(aq) -> 3 Zn(s) + Al2(SO4)3 (aq)
How you know if the above reaction occurs or not? Follow the steps below
Steps to Determine if Single Replacement Reactions occur
1. The element will try to replace the ion of like charge (metal element=cation, non-metal element=anion) from the compound.
2. How do you know the element can replace the ion of like charge in the compound? Use your Activity Series or Strength Chart. If the element is higher up on the chart than the ion of like charge in the compound, the reaction occurs. If the element is lower on the chart than the ion of like charge in the compound, the reaction does not occurs.
3. Make sure that when you are determining if the element is high up on the chart, you use the correct side. Metals use left side of chart and non-metals use right side of chart.
4. If the reaction does occur, the products consist of the replaced ion in its elementary form and a new ionic compound with the reactant element and the other charge ion in the ionic compound. Please make sure that you determine the correct chemical formula for the new ionic compound use the proper procedures.
5. If the reaction does not occur, write No Rxn.