Precipitation Reactions

1. Precipitation Reactions Example: Write the complete balanced molecular equation for the reaction between aqueous solutions of sodium phosphate and calcium acetate. Write the complete ionic equation and the net ionic equation for the reaction.

2. Precipitation Reactions Example: Write the equation for the reaction between NH4Cl (aq) and MgSO4 (aq).

3. Precipitation Reactions NH4Cl (aq) + MgSO4 (aq)  No Reaction • If both products are soluble (aq), then NO REACTION is presumed to occur between the ionic compounds involved. • The reaction mixture simple contains a mixture of soluble ions. • On your exam, you should be able to indicate whether a reaction occurs or not. • If it occurs, write the formulas for the products and balance. • If no reaction occurs, write the words, “No Reaction.” (You should still show your work!)

4. Acids & Bases Acids: Arrhenius definition: substances that ionize to form one or more hydrogen ions (H+) when dissolved in water Bronsted-Lowry definition: Proton (hydrogen ion) donor

5. Acids & Bases Examples of Acids: HCl hydrochloric acid HNO3 nitric acid HC2H3O2 acetic acid H2SO4 sulfuric acid H3PO4 phosphoric acid Note: Acids can form different numbers of H+ ions when they ionize!

6. Acids & Bases Monoprotic acids have one ionizable H in the formula (HA) form a single H+ ion when they ionize HNO3 (aq) H+(aq) + NO3- (aq)

7. Acids & Bases Diprotic acids H2A can form two H+ ion when they ionize completely H2SO4 (aq) 2H+(aq) + SO42- (aq) Polyprotic acids: Have two or more ionizable H’s in the formula Form two or more H+ ions when they ionize completely

8. Acids & Bases Strong Acid: an acid that is a strong electrolyte ionizes completely in solution Weak Acid: an acid that is a weak electrolyte an acid that does not ionize completely

9. Acids & Bases Strong acids: Know the names and formulas of the 7 common strong acids: HCl (aq) hydrochloric acid HBr (aq) hydrobromic acid HI (aq) hydroiodic acid HClO3 chloric acid HClO4 perchloric acid HNO3 nitric acid H2SO4 sulfuric acid

10. Acids & Bases Examples of Weak Acids HF (aq) hydrofluoric acid H3PO4 phosphoric acid HC2H3O2 acetic acid

11. Acids & Bases Bases: substances that accept (react with) H+ ions. any substance that increases the OH- concentration when added to water Examples: NaOH (aq)  Na+ (aq) + OH- (aq) Ca(OH)2 (aq)  Ca2+ (aq) + 2 OH- (aq)

12. Acids & Bases Examples of Bases (cont): Ammonia (NH3) Does not contain OH- Accepts H+ ion from water and increases the OH- concentration in the water NH3(aq) + H2O(l) NH4+ (aq) + OH- (aq) NH3 is a weak electrolyte!!

13. Acids & Bases Strong Base: a base that is a strong electrolyte ionizes completely in solution Weak Base: a base that is a weak electrolyte does not ionize completely in solution

14. Acids & Bases Strong Bases:Know the names and formulas of the strong bases Alkali metal (1A) hydroxides LiOH lithium hydroxide NaOH sodium hydroxide KOH potassium hydroxide RbOH rubidium hydroxide CsOH cesium hydroxide

15. Acids & Bases Strong bases to know (con’t): Heavy alkaline earth metal (2A) hydroxides Ca(OH)2 calcium hydroxide Sr(OH)2 strontium hydroxide Ba(OH)2 barium hydroxide

16. Acids & Bases Examples of Weak Bases: ammonia (NH3) sodium bicarbonate (NaHCO3) baking soda a component of Alka-Seltzer

17. Acid-Base Reactions Reactions between acids and bases are called neutralization reactions. HCl (aq) + NaOH (aq) H2O (l) + NaCl (aq) Salt: any ionic compound whose cation comes from a base and whose anion comes from an acid An ionic compound that is neither an acid nor a base salt

18. Acid-Base Reactions In general the equation for the neutralization of any acid by a metal hydroxide is: acid + metal hydroxide  a salt + water 2 HC2H3O2 (aq) + Ca(OH)2 Ca(C2H3O2)2 (aq) + 2 H2O (l) H3PO4 (aq) + 3 KOH (aq)  K3PO4 (aq) + 3 H2O (l) Neutralization reactions are a type of metathesis reaction.

19. Acid-Base Reactions To predict the products of a neutralization reaction: identify the ions present exchange anions write the correct formulas for the products including physical states write a balanced equation

20. Acid-Base Reactions Example: Write the balanced equation for the reaction between aqueous solutions of HBr and Ca(OH)2.

21. Acid-Base Reactions You can also write complete and net ionic equations for acid-base reactions: • Molecular equation: 2HBr (aq) + Ca(OH)2 (aq)  CaBr2 (aq) + 2H2O (l) • Complete ionic equation: 2 H+ (aq) + 2Br- (aq) + Ca2+ (aq) + 2 OH- (aq)  Ca2+ (aq) + 2 Br- (aq) + 2 H20 (l)

22. Acid-Base Reactions Net ionic equation: H+(aq) + OH-(aq) H2O (l) Note:This is the net ionic equation between any strong acid and strong base. • Complete ionic equation: 2 H+ (aq) + 2Br- (aq) + Ca2+ (aq) + 2 OH- (aq)  Ca2+ (aq) + 2 Br- (aq) + 2 H20 (l)

23. Acid-Base Reactions Example: Write the balanced molecular equation for the reaction between Mg(OH)2 (s) and HCl (aq). Write the complete ionic and net ionic equations.

24. Acid-Base Reactions Example: Write the balanced molecular equation for the reaction between aqueous solutions of sodium hydroxide and phosphoric acid. Write the complete ionic and net ionic equations.

25. Acid-Base Reactions There are many bases that do not contain OH- Na2S NaCN Na2CO3 NaHCO3 These bases react with acids to form gaseous products instead of water.

26. Acid-Base Reactions Examples: KCN(aq) + HCl (aq)HCN(g) + KCl (aq) HBr (aq) + NaHCO3(aq)  NaBr (aq) + H2CO3(aq) but: H2CO3(aq) H2O (l) + CO2 (g) so: HBr (aq) + NaHCO3(aq)  NaBr (aq) + H2O (l) + CO2 (g)

27. Acid-Base Reactions • You should remember the following physical states/reactions for the exam. • H2S (g) • HCN (g) • H2CO3 (aq)  H2O (l) + CO2 (g)