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Double Displacement Reactions

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Presentation on theme: "Double Displacement Reactions"— Presentation transcript:


2 Double Displacement Reactions

3 Double Displacement Reaction
A reaction in which aqueous ionic compounds rearrange cations (A & B) and anions (X & Y), resulting in the formation of new compounds Y X + B A Y + X B A

4 Types of Double Displacement Reactions
A reaction that forms a solid A reaction that forms a gas A reaction that forms water (neutralization)

5 Determining the Products of a Double Displacement Reaction
First determine the ions that make up the reactants. For example, consider the reaction between lithium chloride and lead(II) nitrate: LiCl(aq) + Pb(NO3)2(aq) 

6 LiCl(aq) + Pb(NO3)2(aq)  Lithium ions, Li+ Chloride ions, Cl-
The reactants are composed of four ions: LiCl(aq) + Pb(NO3)2(aq)  Lithium ions, Li+ Chloride ions, Cl- Lead(II) ions, Pb2+ Nitrate ions, NO3-

7 2LiCl(aq) + Pb(NO3)2(aq)  2LiNO3(aq) + PbCl2(s)
To determine the products of the reaction, simply change the pairs of ions. 2LiCl(aq) + Pb(NO3)2(aq)  2LiNO3(aq) + PbCl2(s) Lithium chloride +lead(II) nitrate lithium nitrate + lead(II) chloride

8 MgCl2(aq) + Ca(OH)2(aq)  Mg(OH)2(s) + CaCl2(aq)
Specific Example: MgCl2(aq) + Ca(OH)2(aq)  Mg(OH)2(s) + CaCl2(aq) What “sign” suggests a chemical reaction has occurred? If there is no precipitate formed, there is NO reaction. How can we predict precipitate formation?

9 When will a double displacement reaction occur?
When a precipitate is produced from the reaction of 2 aqueous reactants. To determine which products are precipitates (insoluble in water), you must check your solubility chart When a pure liquid is formed – typically water. When a gas is produced (often CO2, H2, and O2) In summary any reaction where the two products are not aqueous!

10 SOLUBILITY A solution is a homogenous mixture of a solute and a solvent Every solute has its own solubility in a given solvent Solubility is described as the maximum quantity of a solute that will dissolve in a solvent at a given temperature and pressure e.g. adding NaCl to water If a product in a reaction is insoluble a precipitate will form We use a SOLUBILITY TABLE to determine whether a precipitate will form (Nelsons Chemistry 11 p Table 1)


12 What ions can be used to precipitate the following…
Ag+ Nitrate C2H3O2- Ba2+ OH- Phosphate

13 A Reaction That Forms a Solid
Precipitate Reactions CaCl2(aq) + Na2CO3(aq)  (dissolved) (dissolved) CaCO3(s) + 2 NaCl(aq) (solid precipitate) (dissolved) A precipitate is an insoluble solid that is formed by a chemical reaction between two soluble compounds

14 A Reaction That Forms a Gas
Formation of Carbon Dioxide acetic acid + sodium hydrogen carbonate  sodium acetate + carbonic acid CH3COOH(aq) + NaHCO3(s)  NaCH3COO(aq) + H2CO3(aq) NOT the overall reaction because there is NO carbon dioxide!!!

15 Carbonic acid DECOMPOSES into liquid water and carbon dioxide
H2CO3(aq)  H2O(l) + CO2(g) OVERALL Reaction acetic acid + sodium hydrogen carbonate  sodium acetate + water + carbon dioxide CH3COOH(aq) + NaHCO3(s)  NaCH3COO(aq) + H2O(l) + CO2(g)

16 NH4Cl(aq) + NaOH(aq)  NaCl(aq) + NH4OH(aq)
Formation of Ammonia ammonium chloride + sodium hydroxide  sodium chloride + ammonium hydroxide NH4Cl(aq) + NaOH(aq)  NaCl(aq) + NH4OH(aq) NOT the overall reaction because NO ammonia!

17 Ammonium hydroxide DECOMPOSES to form water and ammonia
ammonium hydroxide  water + ammonia NH4OH(aq)  H2O(l) + NH3(g) OVERALL Reaction ammonium chloride + sodium hydroxide  sodium chloride + water + ammonia NH4Cl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) + NH3(g)

18 A Reaction That Forms Water (Neutralization Reactions)
Acid reacts with a Base Products are neither acidic or basic magnesium hydroxide + hydrochloric acid  magnesium chloride + water Mg(OH)2(s) + 2HCl(aq)  MgCl2(aq) + 2H2O(l)

19 then the products include
Summary flowchart to help predict the products of a double displacement reaction If one reactant… + the other reactant… then the products include is an aqueous salt a precipitate is an acid has carbonate ions water and carbon dioxide has ammonium ions has hydroxide ions water and ammonia water

20 Assigned Questions p. 138 # 1, 2, 3 p. 141 – 143 # 4, 5, 7, 9, 10, 11, 12

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