Double displacement reactions

Lesson Outline Double displacement reactions 1. Double displacement reaction forming a precipitate. Solubility rules 2. Double displacement reaction forming a gas. 3. Acid and base neutralization reaction.

Specific expectations C2.1 Use appropriate terminology related to chemical reactions, including, but not limited to: neutralization, precipitate, acidic, and basic. C2.2 Write balanced chemical equations to represent synthesis, decomposition, single displacement, double displacement, and combustion reactions, using the IUPAC nomenclature system. C2.6 Predict the products of double displacement reactions. C3.1 identify various types of chemical reactions, including synthesis, decomposition, single displacement, double displacement, and combustion.

Double displacement reactions Involves the exchange of cations between two ionic compounds, usually in aqueous (water) solution. General equation AB+CD  CB+AD

Left vs. Right Purpose: determine which of the two beakers contains a solution of dissolved NaCl. Choose one of the following reactants to indicate which beaker contains the solution of dissolved NaCl. 1. AgNO3 2. MgSO4 1. Hypothesize which test will indicate the beaker containing dissolved NaCl solution. 2. Write the complete equation of this reaction.

Precipitate: an insoluble solid that is formed by a chemical reaction of two soluble compounds in water.

How to determine if a product is soluble General Solubility Guidelines The higher guideline (1 being the highest) always takes priority over lower guideline numbers. BaCl2 PbCl2 ZnO

Double displacement reactions forming a precipitate How to determine complete the reaction: 1.Switch the cations of the two reactant for form the products. 2.Using the solubility rules, determine if one of the products will form a precipitate. no precipitate = no reaction (NR) 3.Use the zero sum rule to determine the compound ratio of each product. 4.Balance the equation. NaCl (aq) + AgNO3 (aq)  FeCl3 (aq) + Na2SO4 (aq)  FeCl3 (aq) + Na2SO4 (aq) 

Double displacement reactions forming a gas Types of reactions: 1. ionic compound + acid  2. ionic compound + base 

Ionic compound + an acid Reaction 1: double displacement acid Na2CO3 (aq) + 2HCl (aq)  2NaCl (aq) + H2CO3 (aq) Reaction 2: decomposition of acid (product of first reaction) water water H2CO3 (aq)  H2O (l) + CO2 (g) Overall reaction: combine reactions 1 & 2, cancelling out the acid that is on both sides of the overall reaction. H2CO3 (aq) + 2HCl (aq)  2NaCl (aq) + H2O (l) + CO2 (g) (aq) Ex Na2So3 (aq) + HCl (aq) 

Ionic compound + a base Reaction 1: decomposition reaction base NH4CL (aq) + NaOH (aq)  NH4OH (aq) + NaCl (aq) Reaction 2: decomposition of basic product water Na4OH (aq)  NH3 (g) + H2O (l) Overall reaction: combine reactions 1&2, cancel out the base that is present on both side of equation. NH4 (aq) + NaOH (aq)  NaCl (aq) + NH3 (g) + H2O (l) Ex. (NH4)2SO4 (aq) + KOH (aq) 

Acid and base neutralization reactions General Equation: Acid + Base  Salt + water Acid + Base  Salt + water HNO3 (aq) + NaOH (aq)  NaNO3 (aq) + H2O (l) How to complete a neutralization reaction: 1.Use double displacement steps to complete. 2.The formation of water indicates a reaction will occur. HCl (aq) + LiOH (aq) 

In Conclusion A double displacement reaction will occur if: a solid (precipitate) forms a solid (precipitate) forms a gas is produced a gas is produced water is produced water is produced If the following are not produced, no reaction will occur.