Slide 1

Reactions and Solution Stoichiometry Slide 2 Slide 3 Types of Reactions Combination (Synthesis) Decomposition Combustion Single Replacement Double Replacement (Metathesis) Slide 4 Combination/Synthesis Basic Form A + B AB Rxns of elements with oxygen and sulfur C(s) + O(s) CO2 (g) Rxns of metals with halogens 2Na(s) + Cl2 (g) 2NaCl Synthesis rxns with oxides CaO(s) + H2O (l) Ca(OH)2 (s) Slide 5 Decomposition Basic Form AB A + B Binary compounds 2H2O (l) 2H2 (g) + O2 (g) Metal hydroxides Cu(OH)2 (s) CuO(s) + H2O (l) Slide 6 More Decomposition Examples Metal carbonates PbCO3 (s) PbO (s) + CO2 (g) Metal chlorates 2KClO3 (s) 2KCl (s) + 3O2 (g) Oxyacids H2CO3 (l) H2O (l) + CO2 (g) Slide 7 Combustion A substance combines with oxygen, releasing a large amount of energy in the form of light and heat. True or False: The products of every combustion reaction are CO2 and H2O False Slide 8 Combustion Examples Reactive elements combine with oxygen P 4 (s) + 5O 2 (g) P 4 O 10 (s) (This is also a synthesis reaction) The burning of natural gas, wood, gasoline C 3 H 8 (g) + 5O 2 (g) 3CO 2 (g) + 4H 2 O(g) Slide 9 Single Replacement Basic Form A + BY AY + B Metals by other metals 3Mg + 2FeCl3 2Fe + 3MgCl2 Hydrogen in water by another metal 2Na +2H2O H2 + 2NaOH Slide 10 More Single Replacement Hydrogen in an acid by another metal 2Li + 2HCl H2 + 2LiCl Halogens by more active halogens Cl2 + 2KI I2 + 2KCl Slide 11 The Activity Series of the Metals Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead Hydrogen Bismuth Copper Mercury Silver Platinum Gold Metals can replace other metals provided that they are above the metal that they are trying to replace. Metals above hydrogen can replace hydrogen in acids. Metals from sodium upward can replace hydrogen in water Slide 12 The Activity Series of the Halogens Fluorine Chlorine Bromine Iodine Halogens can replace other halogens in compounds, provided that they are above the halogen that they are trying to replace. 2NaCl(s) + F 2 (g) 2NaF(s) + Cl 2 (g) MgCl 2 (s) + Br 2 (g) ???No Reaction Slide 13 Double Replacement (Metathesis) Basic Form AX + BY AY + BX One of the compounds formed is usually a precipitate, an insoluble gas that bubbles out of solution, or a molecular compound, usually water. How do you tell if a precipitate will form? Use your Solubility Rules!!! Slide 14 Mostly Soluble IonSolubilityExceptions NO 3 - SolubleNone ClO 4 - SolubleNone Na + SolubleNone K+K+ SolubleNone NH 4 + SolubleNone Cl -, I - SolublePb 2+, Ag +, Hg 2 2+ SO 4 2- SolubleCa 2+, Ba 2+, Sr 2+, Pb 2+, Ag +, Hg 2+ Slide 15 Mostly Insoluble IonSolubilityExceptions CO 3 2- InsolubleGroup IA and NH 4 + PO 4 3- InsolubleGroup IA and NH 4 + OH - InsolubleGroup IA and Ca 2+, Ba 2+, Sr 2+ S 2- InsolubleGroups IA, IIA, and NH 4 + Slide 16 The Solubility Rule Song!!!! (Sing to Rhythm of 99 Bottles) Alkali metals and ammonium salts,Whatever they may be, Can always be depended on for solubility When asked about the nitrates The answer is always clear, They each and all are soluble, Is all we want to hear. Most every chloride's soluble At least we've always read Save silver, mercury one And chloride of lead Every single sulfate Is soluble, 'Tis said 'Cept barium, strontium, mercury one And calcium and lead. - Hydroxides in general don't dissolve at all But, barium, strontium and calcium Are slightly soluble *but don't forget * Alkali metals and ammonium salts Whatever they may be Can always be depended on For solubility The carbonates are insoluble, It's lucky that it is so, Or else, our marble buildings Would melt away like snow. *but, once again, don't forget * Alkali metals and ammonium salts Whatever they may be Can always be depended on For solubility Slide 17 Net Ionic Equations Written to show only the species that react or undergo change in aqueous solution. Steps for writing net ionic equations 1.Write a balanced molecular equation 2.Rewrite the equation to show the ions that form in solution 3.Identify and cancel spectator ions Spectator Ions do NOT participate in the reaction Slide 18 Sample Problem What compound precipitates when solutions of Fe 2 (SO 4 ) 3 and LiOH are mixed? Write the complete chemical reaction for the reactants above. Write the net ionic equation. List any spectator ions. Slide 19 Another Type of Metathesis Acid/Base Reactions Two Types Neutralization HCl + NaOH NaCl + H2O Gas Formation 2HCl +Na2S H2S(g) + 2NaCl HCl + NaHCO3 NaCl + H2CO3 H2CO3 H2O + CO2(g) Slide 20 Oxidation Reduction Rxns Electrons are transferred Oxidation = Loses Electrons Reduction = Gains Electrons LEO goes GER!! OIL RIG OR Slide 21 Redox Rxn Each sodium atom loses one electron atom gains one electron: Each chlorine atom gains one electron: Slide 22 LEO says GER : LEO says GER : Lose Electrons = Oxidation Sodium is oxidized Gain Electrons = Reduction Chlorine is reduced Slide 23 OIL RIG : OIL RIG : Oxidation Is Loss of electrons Sodium is oxidized Reduction Is Gain of electrons Chlorine is reduced Slide 24 Reducing Agents and Oxidizing Agents The substance reduced is the oxidizing agent The substance oxidized is the reducing agent Sodium is oxidized it is the reducing agent Chlorine is reduced it is the oxidizing agent Slide 25 Rules for Assigning Oxidation #s 1. Atoms in elemental form are always zero 2. Monatomic ions equal the charge on the ion 3. Oxygen is usually -2 (except peroxide is -1) 4. Hydrogen is +1 with NM and -1 with M 5. Fluorine is always -1 6. Sum of the ox #s of all atoms in a neutral compound is zero 7. Sum of the ox #s in a polyatomic ion = the ion charge Slide 26 Sample Problem Determine the oxidation #s for the following: H 2 S S 8 SCl 2 Na 2 SO 3 SO 4 2- Slide 27 Oxidation of metals by acids and salts Similar to single replacement rxns, sometimes called Displacement Rxns General form A + BX AX + B Examples Zn(s) + 2HBr (aq) ZnBr2(aq) + H2 (g) Mn( s ) + Pb(NO3)2( aq ) Mn(NO3)2 ( aq )+ Pb( s ) Slide 28 Rules for Balancing Redox Rxns 1. Assign oxidation #s 2. Determine which species are being oxidized or reduced 3. Divide the equation into 2 half-reactions 4. Balance each half reaction a. Balance elements other than H and O b. Balance O by adding water as needed c. Balance H by adding H+ as needed d. Balance charge by adding e- 5. Multiply half reactions by integers so # of e- are the same in each reaction 6. Add half reactions together, simplifying when you can 7. Check to see if equation is charge and mass balanced Slide 29 Sample Problem Balance the following MnO 4 - (aq) + C 2 O 4 2- (aq) Mn 2+ (aq) + CO 2 (aq) Slide 30 Other Rxns Metal Oxide in Water MO + H2O MOH BaO + H2O Ba(OH)2 Nonmetal Oxide in Water NO + H2O oxyacid N2O3 + H2O HNO2 Slide 31 Solutions Slide 32 Solute A solute is the dissolved substance in a solution. A solvent is the dissolving medium in a solution. Solvent Salt in salt water Sugar in soda drinks Carbon dioxide in soda drinks Water in salt waterWater in soda Slide 33 An electrolyte is: A substance whose aqueous solution conducts an electric current. A nonelectrolyte is: A substance whose aqueous solution does not conduct an electric current. Try to classify the following substances as electrolytes or nonelectrolytes Definition of Electrolytes and Nonelectrolytes Slide 34 Which of the following are electrolytes? Pure water Tap water Sugar solution Sodium chloride solution Hydrochloric acid solution Lactic acid solution Ethyl alcohol solution Pure, solid sodium chloride Slide 35 ELECTROLYTES: NONELECTROLYTES: Tap water (weak) NaCl solution HCl solution Lactate solution (weak) Pure water Sugar solution Ethanol solution Pure, solid NaClAnswers Slide 36 Electrolytes & Net Ionic Equations Ionic CompoundsDissociateIonic CompoundsDissociate NaCl(s) Na + (aq) + Cl - (aq) AgNO 3 (s) Ag + (aq) + NO 3 - (aq) MgCl 2 (s) Mg 2+ (aq) + 2 Cl - (aq) Na 2 SO 4 (s) 2 Na + (aq) + SO 4 2- (aq) AlCl 3 (s) Al 3+ (aq) + 3 Cl - (aq) These compounds should be written as ions in net ionic equations. Slide 37 Other examples of strong acids include: Sulfuric acid, H 2 SO 4 Nitric acid, HNO 3 Hydriodic acid, HI Perchloric acid, HClO 4 Strong acids such as HCl are completely ionized in solution. So they are written as ions in the net ionic equation Weak acids such as lactic acid usually ionize less than 5% of the time. So they are not written as ions in the net ionic equation. Slide 38 Molarity The concentration of a solution measured in moles of solute per liter of solution. mol = M L Slide 39 Sample Problem How many grams of sodium chloride are needed to prepare 1.50 liters of 0.500 M NaCl soln? Slide 40 Serial Dilution It is not practical to keep solutions of many different concentrations on hand, so chemists prepare more dilute solutions from a more concentrated stock solution. M stock V stock = M dilute V dilute Slide 41 Sample Problem What volume of stock (11.6 M) hydrochloric acid is needed to prepare a 3.0 M - 250. ml solution? Slide 42 Sample Problem How many grams of Ca(OH) 2 are needed to neutralize 25.0 mL of 0.100 M HNO 3 ? Slide 43 Sample Problem A sample of 70.5 mg of potassium phosphate is added to 15.0 mL of 0.050 M silver nitrate, resulting in the formation of a precipitate. a. Write the molecular equation for the reaction b. What is the limiting reactant? c. Calculate the theoretical yield, in grams, of the ppt that forms. Slide 44 Sample Problem 45.7 mL of 0.500 H 2 SO 4 is required to neutralize a 20.0 mL sample of NaOH solution. What is the concentration of the NaOH solution?