1. When Will Double Displacement Reactions Happen?

2. Somebodys got to leave the dance! Remember how we compared double- displacement reactions to a dance in which the couples switch partners? A double-displacement reaction only occurs if one of the new couples gets to sneak out! Were outta here!

3. Whats that mean in chemistry? The ions that form one of the possible products has to stay together in some way/ If both products remain dissolved, nothing really happens!

4. Double-Displacement Reactions The ions of two ionic compounds exchange places (often in an aqueous solution) to form two new compounds, one of which is: – A precipitate – A gas that bubbles out (effervesces) – A molecular compound, usually water

5. What does this mean? When ionic substances dissolve in water, the cations and anions separate. They exist as separate ions surrounded by water. A reaction happens if something occurs that changes this. – FORMATION OF A PRECIPITATE – FORMATION OF A GAS – FORMATION OF WATER

6. Formation of a Precipitate When the cations of one reactant react with the anions of another reactant to form an insoluble or slightly soluble compound. Check the solubility chart: S = soluble I = insoluble = slightly soluble If one of the products is insoluble or slightly soluble, a reaction happens. AgNO 3 (aq) + NaCl(aq) AgCl(s) + NaNO 3 (aq)

7. Formation of a Gas If one of the products is an insoluble gas that bubbles out of the mixture, the reaction happens. FeS(s) + 2HCl (aq) H 2 S(g) + FeCl 2 (aq)

8. Formation of Water If water, a very stable molecular compound, is formed, the reaction happens. HCl (aq) + NaOH(aq) NaCl(aq) + H 2 O(l)

9. Sometimes, nothing happens If none of the conditions described above happens, the ions remain separated, and there is no reaction. Remember: A double-displacement happens if the products of ion exchange include one of the following: – Precipitate – Gas – Water