1. Unit 2 - Chemical Reactions

2. Double displacement occurs between ions in aqueous solution. A reaction will occur when a pair of ions come together to produce at least one of the following: –a precipitate –a gas –water or some other non-ionized substance. Basic form: AX + BY → AY + BX

3. Example Formation of precipitate. –NaCl (aq) + AgNO 3 (aq)→ NaNO 3 (aq) + AgCl(s) –BaCl 2 (aq) +Na 2 SO 4 (aq) →2NaCl(aq) +BaSO 4 (s) Formation of a gas. –HCl(aq) + FeS(s) → FeCl 2 (aq) +H 2 S(g) Formation of water. (If the reaction is between an acid and a base it is called a neutralization reaction.) HCl(aq) + NaOH(aq)→ NaCl(aq) + H 2 O(l) Formation of a product which decomposes. CaCO 3 (s) +HCl(aq)→ CaCl 2 (aq) + CO 2 (g)+H 2 O(l)

4. PREDICTING PRECIPITATION REACTIONS USING SOLUBILITY RULES How do you determine the state of the products? Use the solubility rules to decide whether a product of an ionic reaction is insoluble in water and will thus form a precipitate ( an insoluble compound formed during a chemical reaction in solution. ) Use (S) If a compound is soluble in water then it should be shown as being in aqueous solution  use (aq)

5. Examples: If we add a solution of KCl to a AgNO 3 solution will a precipitate form? We first write a predicted reaction. KCl (aq) + AgNO 3(aq)  KNO 3 + AgCl

6. Then we look at the solubility table to see if any of the products are insoluble in water. We see that the table indicates that AgCl is insoluble - most chlorides are soluble except for Ag +, Hg 2+, Hg 2 2+ and Pb 2+ The molecular equation then becomes: KCl(aq) + AgNO 3(aq)  KNO 3(aq) + AgCl (s)

7. If we add a solution of NaNO 3 to an NH 4 Cl solution will a precipitate form? The predicted equation then becomes: NaNO 3(aq) + NH 4 Cl (aq)  NaCl + NH 4 NO 3 We see that the table indicates that both compounds are soluble - most chlorides are soluble, NaCl is soluble, and nitrates are soluble as well as NH 4 + compounds, so mixing these two solutions gives no precipitates, no reaction results. After the  we would write N. R. for no reaction.

8. Practice Use your solubility table to determine whether the following compounds are soluble in water and indicate the state. Ionic CompoundChemical formulaSoluble/Insoluble?State lead (II) sulfate ammonium sulfide silver nitrate silver chloride calcium carbonate ammonium hydroxide barium hydroxide

9. Examples Predict if a new product will form when a solution of sodium chloride is mixed with a solution of potassium bromide. Write the balanced chemical equation including states.

10. Practice Determine the products and write the balanced chemical reaction for the following. Include the states for all reactants and products. 1.A solution of lead (II) nitrate mixed with a solution of sodium chloride. 2.A solution of sodium sulfate is mixed with a solution of calcium chloride 3.A solution of magnesium acetate mixed with a solution of silver nitrate. 4.A solution of strontium nitrate mixed with a solution of sodium sulfate. 5.A solution of barium nitrate mixed with ammonium phosphate.

11. IONIC EQUATIONS Net Ionic equations-only involve those chemical species which are involved in a chemical reaction. All spectator ions are eliminated. Spectator ions-those ions which do not participate in the chemical reaction but are present in the reaction mixture Write the molecular, ionic, and net ionic equations for the reaction of an aqueous solution of CaCl 2 and an aqueous solution of Na 2 CO 3.

12. 1) the molecular equation is: CaCl 2(aq) + Na 2 CO 3(aq)  CaCO 3(s) +2NaCl (aq) 2) the ionic equation is: Ca 2+ (aq) + 2 Cl - (aq) + 2 Na + (aq) + CO 3 2- (aq)  CaCO 3(s) + 2 Na + (aq) + 2 Cl - (aq) 3) the net ionic equation is: Ca 2+ (aq) + CO 3 2- (aq)  CaCO 3(s) molecular ionic net ionic