Presentation on theme: "Types of Chemical Reactions and Solution Stoichiometry"— Presentation transcript:
1Types of Chemical Reactions and Solution Stoichiometry
2Classification of Matter Solutions are homogeneous mixtures
3Solute Solvent A solute is the dissolved substance in a solution. Salt in salt waterSugar in soda drinksCarbon dioxide in soda drinksSolventA solvent is the dissolving medium in a solution.Water in salt waterWater in soda
4Saturation of Solutions A solution that contains the maximum amount of solute that may be dissolved under existing conditions is saturated.A solution that contains less solute than a saturated solution under existing conditions is unsaturated.A solution that contains more dissolved solute than a saturated solution under the same conditions is supersaturated.
5Electrolytes vs. Nonelectrolytes The ammeter measures the flow of electrons (current)through the circuit.If the ammeter measures a current, and the bulbglows, then the solution conducts.If the ammeter fails to measure a current, and thebulb does not glow, the solution is non-conducting.
6Definition of Electrolytes and Nonelectrolytes An electrolyte is:A substance whose aqueous solution conductsan electric current.A nonelectrolyte is:A substance whose aqueous solution does notconduct an electric current.Try to classify the following substances aselectrolytes or nonelectrolytes…
8Answers… ELECTROLYTES: NONELECTROLYTES: Tap water (weak) NaCl solution HCl solution Lactate solution (weak) Pure water Sugar solution Ethanol solution Pure, solid NaClBut why do some compounds conduct electricity insolution while others do not…?
10Some covalent compounds IONIZE in solution Covalent acids form ions in solution, with thehelp of the water molecules.For instance, hydrogen chloride molecules,which are polar, give up their hydrogens towater, forming chloride ions (Cl-) andhydronium ions (H3O+).
11Strong acids such as HCl are completely ionized in solution. Other examples of strong acids include:Sulfuric acid, H2SO4Nitric acid, HNO3Hydriodic acid, HIPerchloric acid, HClO4Hydrobromic acid, HBr
12Weak acids such as lactic acid usually ionize less than 5% of the time. Many of these weaker acidsare “organic” acidsthat contain a “carboxyl”group.The carboxyl group does not easily give up itshydrogen.
13Because of the carboxyl group, organic acids are sometimes called “carboxylic acids”. Other organic acids and their sources include:Citric acid – citrus fruitMalic acid – applesButyric acid – rancid butterAmino acids – proteinNucleic acids – DNA and RNAAscorbic acid – Vitamin CThis is an enormous group of compounds; theseare only a few examples.
14However, most covalent compounds do not ionize at all in solution. Sugar (sucrose – C12H22O11),and ethanol (ethyl alcohol – C2H5OH) do notionize -That is why they are nonelectrolytes!
15MolarityThe concentration of a solution measured in moles of solute per liter of solution.mol = ML
16Preparation of Molar Solutions Problem: How many grams of sodium chloride are needed to prepare 1.50 liters of M NaCl solution?Step #1: Ask “How Much?” (What volume to prepare?)Step #2: Ask “How Strong?” (What molarity?)Step #3: Ask “What does it weigh?” (Molar mass is?)1.500 L0.500 mol58.44 g= 43.8 g1 L1 mol
17Serial DilutionIt is not practical to keep solutions of many different concentrations on hand, so chemists prepare more dilute solutions from a more concentrated “stock” solution.Problem: What volume of stock (11.6 M) hydrochloric acid is needed to prepare 250. mL of 3.0 M HCl solution?MstockVstock = MdiluteVdilute(11.6 M)(x Liters) = (3.0 M)(0.250 Liters)x Liters = (3.0 M)(0.250 Liters)11.6 M= L
18Single Replacement Reactions A + BX AX + BBX + Y BY + XReplacement of:Metals by another metalHydrogen in water by a metalHydrogen in an acid by a metalHalogens by more active halogens
19The Activity Series of the Metals Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead Hydrogen Bismuth Copper Mercury Silver Platinum GoldMetals can replace other metalsprovided that they are above themetal that they are trying toreplace.Metals above hydrogen canreplace hydrogen in acids.Metals from sodium upward canreplace hydrogen in water
20The Activity Series of the Halogens Fluorine Chlorine Bromine IodineHalogens can replace otherhalogens in compounds, providedthat they are above the halogenthat they are trying to replace.2NaCl(s) + F2(g) 2NaF(s) + Cl2(g)???MgCl2(s) + Br2(g) No Reaction???
22Solubility Rules – Mostly Insoluble IonSolubilityExceptionsCO32-InsolubleGroup IA and NH4+PO43-OH-Group IA and Ca2+, Ba2+, Sr2+S2-Groups IA, IIA, and NH4+
23Oxidation and Reduction (Redox) Electrons are transferred Spontaneous redox rxns can transfer energy Electrons (electricity) Heat Non-spontaneous redox rxns can be made to happen with electricity
24Oxidation and Reduction An old memory device for oxidation and reduction goes like this…LEO says GERLose Electrons = OxidationGain Electrons = Reduction
25Oxidation Reduction Reactions (Redox) Each sodium atom loses one electron:Each chlorine atom gains one electron:
26LEO says GER :Lose Electrons = OxidationSodium is oxidizedGain Electrons = ReductionChlorine is reduced
27Rules for Assigning Oxidation Numbers Rules 1 & 2 The oxidation number of any uncombined element is zero2. The oxidation number of a monatomic ion equals its charge
28Rules for Assigning Oxidation Numbers Rules 3 & 4 3. The oxidation number of oxygen incompounds is -24. The oxidation number of hydrogen in compounds is +1
29Rules for Assigning Oxidation Number Rule 5 5. The sum of the oxidation numbers in the formula of a compound is 02(+1) + (-2) = 0H O(+2) + 2(-2) + 2(+1) = 0Ca O H
30Rules for Assigning Oxidation Numbers Rule 6 6. The sum of the oxidation numbers in theformula of a polyatomic ion is equal toits chargeX + 4(-2) = -2S OX + 3(-2) = -1N O X = +5 X = +6
31Reducing Agents and Oxidizing Agents The substance reduced is the oxidizing agent The substance oxidized is the reducing agentSodium is oxidized – it is the reducing agentChlorine is reduced – it is the oxidizing agent
32Trends in Oxidation and Reduction Active metals: Lose electrons easily Are easily oxidized Are strong reducing agentsActive nonmetals: Gain electrons easily Are easily reduced Are strong oxidizing agents
33Redox Reaction Prediction #1 Important OxidizersFormed in reactionMnO4- (acid solution)MnO4- (basic solution)MnO2 (acid solution)Cr2O72- (acid)CrO42-HNO3, concentratedHNO3, diluteH2SO4, hot concMetallic IonsFree HalogensHClO4Na2O2H2O2Mn(II)MnO2Cr(III)NO2NOSO2Metallous IonsHalide ionsCl-OH-O2