Common Types of Reactions

Combination Rxns Between non-metals to give a molecular product Between metal and non-metal to yield an ionic product Between compounds N 2 (g) + O 2 (g) 2NO(g) 4Al(s) + 3O 2 (g) 2Al 2 O 3 (s) NH 3 (g) + HCl(g) NH 4 Cl(s) (Al 3+, O 2- )

Decomposition Rxns CuSO 4. 5H 2 O(s) CuSO 4 (s) + 5H 2 O(g) MgCO 3 (s) MgO(s) + CO 2 (g)

Single Replacement Rxns Zn(s) + 2HCl(aq) ZnCl 2 (aq) + H 2 (g) Na(s) + 2H 2 O(l) 2NaOH(aq) + H 2 (g)

Double Replacement (Metathesis) Rxns Precipitation Reactions Acid-Base (Neutralization) Reactions HNO 3 (aq) + NaOH(aq) H 2 O(l) + NaNO 3 (aq) acid base salt Pb(NO 3 ) 2 (aq) + 2KI(aq) PbI 2 (s) + 2KNO 3 (aq) yellow solid

Acid-Base (Neutralization) Rxns Oxidation-Reduction(Redox, Electron Transfer) Rxns Precipitation Rxns HNO 3 (aq) + NaOH(aq) H 2 O(l) + NaNO 3 (aq) Zn(s) + 2HCl(aq) ZnCl 2 (aq) + H 2 (g) Pb(NO 3 ) 2 (aq) + 2KI(aq) PbI 2 (s) + 2KNO 3 (aq) More Than One Way to Categorize

More About Acids and Bases... Acids Taste sour (vinegar, lemon juice) Turn litmus red React with bases to make H 2 O React with many metals to make H 2 React with carbonates to make CO 2 and H 2 O Bases Taste bitter Turn litmus blue React with acids to make water Feel slippery

The Arrhenius View Acid - yields H + when added to water HCl (g) + H 2 O (l)  H + (aq) + Cl - (aq) unbalanced Base - yields OH - when added to water NaOH (s) + H 2 O (l)  Na + (aq) + OH - (aq) unbalanced

Arrhenius View of Neutralization acid + base a salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O

The Brønsted View More general approach, not limited to water Brønsted acid = H + donor Brønsted base = H + acceptor Neutralization = “proton” (H + ) transfer

Why is HCl a Brønsted Acid? hydronium ion, H 3 O +

acidbase Why is Ammonia a Brønsted Base?

Redox e- transfer rxns

Oxidation-Reduction 2Fe (s) + 3Cl 2 (g) 2FeCl 3 (s) Fe 3+, Cl - Fe is oxidized (loses e-): Fe Fe e- Cl 2 is reduced (gains e-): Cl 2 + 2e - 2Cl - reducing agent (supplier of e-): Fe oxidizing agent (acceptor of e-): Cl 2

Adding Half Rxns Yields Overall Rxn 3Cl 2 + 6e - 6Cl - reduction 2Fe 2Fe e- oxidation 2Fe + 3Cl 2 2FeCl 3 overall

Problem: What is the oxidizing agent when copper reacts with silver nitrate to form silver and copper(II) nitrate? Cu(s) + 2AgNO 3 (aq) Cu(NO 3 ) 2 (aq) + 2Ag(s) Ag + is the oxidizing agent (consumes electrons from Cu) Ag + + 1e - Ag Cu Cu e -

Problem: Is Cl reduced or oxidized when KClO 3 decomposes? 2KClO 3 2KCl + 3O 2 ?

Tracking e- Transfers Oxidation State (Oxidation Number): The charge an element carries either alone or when combined with other elements in a compound. oxidation: O# goes up reduction: O# goes down change in O# tells whether ox or red occurs

Simple Oxidation Number Rules 1.Free element O# = zero. Fe, Cl 2, Na, Pb, H 2, O 2, P 4 = 0 2. In monatomic ions, the O# = ion charge Li +, Li = +1; Fe 3+, Fe = +3; O 2-, O = -2 3.Certain elements have same O# in ~all their compounds. O usually -2, H usually  4.  (O# in cmpd) = overall charge of cmpd/ion. More extensive rules are in text...

Problem: Is Cl reduced or oxidized when KClO 3 decomposes ? 2KClO 3 2KCl + 3O Oxidation number drops (+5 to -1), so Cl is reduced. 1 potassium + 1 chlorine + 3 oxygens = 0 charge on KClO 3 1(+1) + 1(?) + 3(-2) = 0 ? = +5

HCO 3 - 1(+1) + 1(?) + 3x(-2) = -1 ? = O# of C = +4 Problem: What are the oxidation numbers of all the elements in HCO 3 - ? O = -2 H = +1 O#’s according to rules C = ? no simple rule 1 hydrogen + 1 carbon + 3 oxygens = -1 charge anion

The Activity Series for Metals Not important to memorize any of this. You’ll see it again next semester.

Net Ionic Equations To Describe Pptn and A-B Rxns

Problem: Pb(NO 3 ) 2 and NaCl  ? NaCl solution: contains Na + (aq) + Cl - (aq) Pb(NO 3 ) 2 solution: contains Pb 2+ (aq) + NO 3 - (aq) How do we know ions are separated?

Problem: Pb(NO 3 ) 2 and NaCl  ? New Combinations? Na + with NO 3 - NaNO 3 is a strong electrolyte  ions stay separated Represent as “NaNO 3 (aq)” or “Na + (aq) + NO 3 - (aq)” Pb 2+ with Cl - PbCl 2 is a weak electrolyte  ions mostly together Represent as “PbCl 2 (s)”

Ionic equation shows ions in correct state Net ionic equation excludes spectator ions 2Na + (aq) + 2Cl - (aq) + Pb 2+ (aq) + 2NO 3 - (aq) --> PbCl 2 (s) + 2Na + (aq) + 2NO 3 - (aq) Pb 2+ (aq) + 2Cl - (aq) --> PbCl 2 (s) Problem: Pb(NO 3 ) 2 and NaCl  ?

Summary Whole formula equation Ionic equation Net ionic equation Pb 2+ (aq) + 2Cl - (aq) PbCl 2 (s) 2NaCl(aq) + Pb(NO 3 ) 2 (aq) PbCl 2 (s) + 2NaNO 3 (aq) 2Na + (aq) + 2Cl - (aq) + Pb 2+ (aq) + 2NO 3 - (aq) PbCl 2 (s) + 2Na + (aq) + 2NO 3 - (aq)

Problem: Write the net ionic equation for the reaction of sodium hydroxide and acetic acid in water. whole formula ionic eqn net ionic eqn

NaOH(aq) + HC 2 H 3 O 2 (aq) NaC 2 H 3 O 2 (aq) + H 2 O(l) OH - + HC 2 H 3 O 2 C 2 H 3 O H 2 O (l) Na + + OH - + HC 2 H 3 O 2 Na + + C 2 H 3 O H 2 O strong electrolyte weak electrolyte strong electrolyte weak/non- electrolyte whole formula ionic eqn net ionic eqn Problem: Write the net ionic equation for the reaction of sodium hydroxide and acetic acid in water.

Ca 2+ + CO 3 2- CaCO 3 NH 3 + H + NH 4 + Zn + 2HCl ZnCl 2 + H 2 Ca + F 2 CaF 2 Precipitation Acid-Base Redox (Single Displacement) Redox (Combination) Problem: Classify the following reactions.