3General Properties of Aqueous Solutions Homogeneous mixtures of two or more pure substances.The solvent in greatest abundance.All other substances are solutes.If water is the solvent the solution is aqueous
4Electrolytic Properties whether or not solutions conduct electricity.If ions form in solution, the substance is an electrolyte and the solution conducts electricity. e.g. NaCl.If no ions form, the substance is a nonelectrolyte. e.g. sucrose.Ions form in solution through the process of dissociation.
5Dissociation Solid does not exist as a well-ordered crystal. Each ion surrounded by a shell of water molecules.cations have oxygen end of water pointing in.anions have hydrogen end of water pointing in.Ions move to cause electric current to flow through solution.Electrolytes - Soluble ionic compoundsNon-electrolytes Molecular compounds
6ElectrolytesA strong electrolyte dissociates completely when dissolved in water.ionic compounds, many acids & bases.A weak electrolyte only dissociates partially when dissolved in water.weak acids and bases.
7Solvation Equations A substance dissolves in a solvation reaction: sugar is a non-electrolyte:C12H22O11 (s) → C12H22O11 (aq)soluble ionic compounds undergo dissociation in solution; break up into constituent ions:NaCl (s) → Na1+(aq) + Cl1-(aq)(this represents both solvation and dissociation)
8to write a dissociation equation for any ionic compound identify the cation and anion, then write the balanced equation:Al2(SO4)3 (s) contains Al3+ and SO42- ions.When it dissociates you get 2 Al3+ and 3 SO42- ions:Al2(SO4)3 (s) → 2 Al3+(aq) SO42-(aq)(make sure the equation is balanced)
9Write dissociation equations for the ionic substances in questions 4 Write dissociation equations for the ionic substances in questions 4.15 and 4.16
10Precipitation Reactions When a mixture of soluble ions forms a compound that is insoluble, a precipitate is formed.Pb(NO3)2 (aq) + 2 KI(aq) PbI2 (s) + 2 KNO3 (aq)
11Solubility Guidelines for Ionic Compounds Solubility is the amount of a substance that can be dissolved in a given quantity of solvent at that temperature.Measured in g/100g H2O, or mol/LSolubility < mol/L is insoluble.Experimental observations have led to empirical guidelines for predicting solubility.
12Solubility of Selected Ions (soluble > 0.1 mol/L) Anion+Cation=Solubilityanygroup 1 metal ion (Li1+, Na1+, K1+, Rb1+, Cs1+)issolubleammonium ion (NH41+)nitrate ion (NO31-)chlorate ion (ClO31-)acetate ion(CH3COO1-)Ag1+any other cationnot solublechloride (Cl1-),bromide (Br1-), iodide (I1-)Ag1+, Pb2+, Hg22+, or Cu1+Ag1+, Pb2+, Hg22+, Hg2+ or Cu1+Sulfate (SO42-)Ca2+, Sr2+, Ba2+, Ra2+, Ag1+, Pb2+, Hg22+ Hg2+Sulfide (S2-)group 1 & 2 elements, NH41+Hydroxide (OH1-)group 1 elements & NH41+, Ca2+, Sr2+, Ba2+Phosphate (PO43-) Carbonate (CO32-) Sulfite (SO32-)Oxide (O2-)group 1 elements & NH41+
13Predicting Solubility Na2Ssoluble, because Na is an alkali metal (group 1)NH4Clsoluble, because the NH41+ ion is soluble with any anionCuNO3soluble, because NO31- is soluble with any cationAgCH3COOinsolubleMg(CH3COO)2solublePbCl4soluble; in this compound the Pb is 4+PbCl2insoluble; in this compound the Pb is 2+
16Metathesis (Exchange) Reactions Metathesis comes from a Greek word that means “to transpose”AgNO KCl AgCl (s) + KNO3 (aq)
17Metathesis (Exchange) Reactions Metathesis comes from a Greek word that means “to transpose”It appears the ions in the reactant compounds exchange, or transpose, ionsAgNO KCl AgCl (s) + KNO3 (aq)
18Metathesis (Exchange) Reactions Metathesis comes from a Greek word that means “to transpose”It appears the ions in the reactant compounds exchange, or transpose, ionsAgNO KCl AgCl + KNO3
19Metathesis (Exchange) Reactions Metathesis comes from a Greek word that means “to transpose”It appears the ions in the reactant compounds exchange, or transpose, ionsalways indicate the phase of the substance, where knownmost are reactions of ionic compoundsAgNO3 (aq) + KCl (aq) AgCl (s) + KNO3 (aq)
21AgNO3 (aq) + KCl (aq) AgCl (s) + KNO3 (aq) Molecular EquationThe molecular equation lists the reactants and products in their molecular form.AgNO3 (aq) + KCl (aq) AgCl (s) + KNO3 (aq)
22Complete Ionic Equation All strong electrolytes are dissociated into their ions.This more accurately reflects the species that are found in the reaction mixture.Ag+ (aq) + NO3- (aq) + K+ (aq) + Cl- (aq) AgCl (s) + K+ (aq) + NO3- (aq)
23Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) AgCl (s) + K+(aq) + NO3-(aq) Net Ionic EquationTo form the net ionic equation, cross out anything that does not change from the left side of the equation to the right.Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) AgCl (s) + K+(aq) + NO3-(aq)
24Ag+(aq) + Cl-(aq) AgCl (s) Net Ionic EquationTo form the net ionic equation, cross out anything that does not change from the left side of the equation to the right.The only things left in the equation are those things that change (i.e., react) during the course of the reaction.Ag+(aq) + Cl-(aq) AgCl (s)
25Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) AgCl (s) + K+(aq) + NO3-(aq) Net Ionic EquationTo form the net ionic equation, cross out anything that does not change from the left side of the equation to the right.The only things left in the equation are those things that change (i.e., react) during the course of the reaction.Those things that didn’t change (and were deleted from the net ionic equation) are called spectator ions.Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) AgCl (s) + K+(aq) + NO3-(aq)
26Writing Net Ionic Equations Write a balanced molecular equation.Dissociate all strong electrolytes. Write the complete ionic equation.Cross out anything that remains unchanged from the left side to the right side of the equation.Write the net ionic equation with the species that remain.
27Write the balanced molecular equation, complete ionic equation and net ionic equation for the following:FeCl2 (aq) + K2S (aq) AlBr3 (aq) + NaOH (aq) (NH4)3PO4 (aq) + Ca(NO3)2 (aq) Aqueous solutions of silver nitrate and sodium carbonate react.Aqueous solutions of barium chloride and potassium sulfate react.
28Complete questions 4. 22 and 4. 24 Complete questions 4.22 and In each reaction with a precipitate write the balanced molecular equation, complete ionic equation and net ionic equationHand in on:
29Acids:2 definitions:Substances that increase the concentration of H1+ when dissolved in water (Arrhenius).Proton donors (Brønsted–Lowry).If an acid can donate more than one proton it is diprotic or triprotic.
30Acids Strong acids dissociate completely in water There are only seven strong acids:Hydrochloric (HCl)Hydrobromic (HBr)Hydroiodic (HI)Nitric (HNO3)Sulfuric (H2SO4)Chloric (HClO3)Perchloric (HClO4)
31Bases:Substances that increase the concentration of OH1- when dissolved in water (Arrhenius).Proton acceptors (Brønsted–Lowry).
32Bases Strong bases dissociate completely in water. The strong bases are the soluble salts of hydroxide ion:Alkali metals (LiOH, NaOH, etc)Ca(OH)2, Sr(OH)2, Ba(OH)2
33Weak Acids and Bases are weak electrolytes. Therefore, they are partially ionized in solution.HF(aq) is a weak acid; most acids are weak acids.We write the ionization of HF as:HF H1+ + F1-
34Identifying Strong & Weak Electrolytes Compounds can be classified as by looking at their solubility:Strong electrolytes:Ionic compounds.Strong acids are strong electrolytes.Weak electrolytes:Weak acids and bases.Nonelectrolytes:All other compounds.
36Acid-Base ReactionsIn an acid-base reaction, the acid donates a proton (H+) to the base.
37Neutralization Reactions When solutions of an acid and a base are combined, the products are a salt and water.Molecular Equation:HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)acid base salt watera salt is any non-acidic or basic ionic compound
38Neutralization Reactions When a strong acid reacts with a strong base, the complete ionic equation is…HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)H+ (aq) + Cl- (aq) + Na+ (aq) + OH-(aq) Na+ (aq) + Cl- (aq) + H2O (l)
39Neutralization Reactions When a strong acid reacts with a strong base, the net ionic equation is…HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)H+ (aq) + Cl- (aq) + Na+ (aq) + OH-(aq) Na+ (aq) + Cl- (aq) + H2O (l)H+ (aq) + OH- (aq) H2O (l)
42Gas-Forming Reactions Reaction of sulfides with acid gives rise to H2S(g).FeS (s) + 2 HCl (aq) FeCl2 (aq) + H2S (g)Reaction of sulfites with acid gives rise to SO2 (g).SrSO3 (s) + 2 HI (aq) SrI2 (aq) + SO2 (g) + H2O (l)
43Gas Forming ReactionsAcid with carbonate or hydrogen carbonate forms CO2:CaCO3 (s) + HCl (aq) CaCl2 (aq) + CO2 (g) + H2O (l)NaHCO3 (aq) + HBr (aq) NaBr (aq) + CO2 (g) + H2O (l)Bases with ammonium compounds gives ammonia gas:NH4Cl (aq) + NaOH (aq) NH3 (g)+ H2O (l) + NaCl (aq)
45Oxidation-Reduction Reactions Involve the transfer of electronsAn oxidation occurs when an atom or ion loses electrons. (LEO)A reduction occurs when an atom or ion gains electrons. (GER)In all redox reactions, one species is reduced at the same time as another is oxidized.
46Oxidation Numbersused to determine if an oxidation-reduction reaction has occurredwe assign a charge to each element in a neutral compound or charged entity.these charges, real or virtual, are called oxidation numbers
47Rules of Oxidation Numbers Elements have an oxidation number of 0.The oxidation number of a monatomic ion is the same as its charge.Oxygen has an oxidation number of 2- (except peroxides, O22-)Hydrogen has an oxidation number of 1+ (except hydrides, H1-)The sum of the oxidation numbers in a neutral compound is 0.The sum of the oxidation numbers in a polyatomic ion is the charge on the ion.
48Calculation of Oxidation Numbers H2O- H is 1+, O is 2-H2O2H is 1+, O is 1-AlH3Al is 3+, H is 1-CaCl2Ca is 2+, Cl is 1-PbS2Pb is 4+, S is 2-Mn3N7Mn is 7+, N is 3-H2SO4H is 1+, S is 6+, O is 2-Cr2O72-Cr is 6+, O is 2-
50Recognizing Oxidation and Reduction Consider the following balanced chemical equation:3 Cu Al 3 Cu Al3+Let’s apply what we know about oxidation numbers to this equation:3 Cu Al 3 Cu Al3+O.N
51copper goes from 2+ to 0;it’s charge got lower, so it is reduced (it gained electrons).The aluminum goes from 0 to 3+;it’s charge got greater, so it is oxidized (it lost electrons):reduction (gained 2 electrons each)┌─────────────┐3 Cu Al 3 Cu Al3+O.N└──────────────┘oxidation (lost 3 electrons each)The total number of electrons lost and gained is the same; 6
52A redox equation is balanced if: it is balanced for atoms on each side.the total electrons lost and gained are equal.A bit of terminology;the substance that is oxidized is the reducing agent.The substance that is reduced is the oxidizing agent.
53Our equation now looks like this: oxidizing agentreduction (gained 2 electrons each)┌───────────┐3 Cu Al 3 Cu Al3+O.N└────────────┘oxidation (lost 3 electrons each)reducing agent
56Displacement Reactions Also called single replacement reactions.In displacement reactions, one metal replaces another metal in an ionic compound or acids.The general pattern is:A + BX AX + BwhereA is a neutral metalB is a metal cationX is any anion
57Example: metals produce hydrogen gas with acids. Consider Mg and HCl: Mg(s) + 2 HCl(aq) MgCl2 (aq) + H2 (g)the metal is oxidizedH1+ is reduced.
58Example: metals can be oxidized in the presence of a salt: Fe(s) + Ni(NO3)2 (aq) Fe(NO3)2 (aq) + Ni(s)The net ionic equation shows the redox chemistry well:Fe(s) + Ni2+(aq) Fe2+(aq) + Ni(s)iron has been oxidized to Fe2+Ni2+ has been reduced to Ni.
64The metals at the top are active metals. The metals at the bottom are noble metals.A metal in the activity series can only be oxidized by a metal ion below it.For example:If Cu + Ag1+ ions:Cu2+ ions are formed because Cu is above Ag in the activity series:Cu(s) + 2 AgNO3 (aq) Cu(NO3)2 (aq) + 2 Ag(s)orCu(s) + 2 Ag1+(aq) Cu2+(aq) + 2 Ag(s)
67Molar Concentrationindicates the amount of solute dissolved in a given quantity of solvent or solution.is the most common measure of concentration used in the lab.is the number of moles of solute, per litre of solution (mol/L, mol∙L-1).is also called Molarity (M).for instance, 0.12 mol/L ≡ 0.12 M
68Concentration of an Electrolyte the concentration of the ions may be different than the calculated concentration of the substance in solution:If the aluminum sulfate is a mol/L solution, thenAl2(SO4)3 (s) → 2 Al3+(aq) SO42-(aq)0.200 mol/L 2(0.200 mol/L) 3(0.200 mol/L)= mol/L = mol/L
69Write the equation for the dissociation of the following ionic substances. Calculate the concentration of each ion in solution:0.35 mol/L NaOH1.12 mol/L (NH4)2CO30.056 mol/L V3(PO4)5
70Calculating MolarityMolar concentration (molarity) calculations consist of 3 variables:concentration (mol/L)number of moles (mol)volume (L)If we know any two of these, we can calculate the third.Dimensional analysis is very helpful in these calculations.
71Examples of MolarityCalculate the molar concentration when mol of CuSO4 is dissolved in 1.1 L of solution.molar concentration = moles of solutevolume of solutionc = nv= mol1.1 L= 0.23 mol/L (2 s.d.)
72Calculate the molar concentration when 28 Calculate the molar concentration when 28.2 g of KNO3 is dissolved in 750. mL of solution.given 28.2 g ; need to convert mass to molesmolar mass: KNO31 x K = 1 x g/mol1 x N = 1 x g/mol3 x O = 3 x g/molg/molmoles of substance = g= molmolar mass: KNO31 x K = 1 x g/mol1 x N = 1 x g/mol3 x O = 3 x g/molg/molmoles of substance = g = molvolume must be reported in L:750. mL x L = L1000 mLmolar concentration:c = n = molV L= mol/L
73volume must be reported in L: 750. mL x L = L1000 mLmolar concentration:c = n = molV L= mol/L
74Calculate the volume of solution made with 0 Calculate the volume of solution made with mol of sodium phosphate in a 2.00 M solution.c = nVV = n = molc mol/L= L
75How many moles are present in 4. 50 L of a 0 How many moles are present in 4.50 L of a mol/L solution of magnesium nitrate?c = nVn = cV= (0.025 mol/L)(4.50 L)= 0.11 mol
77Other Measures of Concentration based on weight to weight (gram to gram) concentrationParts per hundred (percent, %) 1 g of a solute per 100 grams of solution.One part in 102.equal to 1 g of a solute in 100 g of solution, or 100 mL of solution.
78Parts per ..... Parts per thousand one gram for every 1000 g of solution.equivalent to:one drop of ink in a cup of waterone second per 17 minutes."Parts per thousand" is often used to record the salinity of seawater.
79Parts per ... Parts per million (ppm) one gram of solute for every g of solution (1 mg/kg, 1 μg/g)equivalent to:one drop of ink in a 150 litre (40 gallon) drum of water1 L of ink in Riversdale pool (assume 106 L)1 s in daysUsed to measure levels of metals, nutrients and toxic substances in the environment
80Parts per ... Parts per billion (ppb) one gram of solute for every 109 grams of solution (1 ng/g, 1 μg/kg)equivalent to:1 gram of ink in Riversdale pool.1 second in yearsis the level of activity of hormones in living system.some carcinogens and toxins are active at this level.
81Parts per ... Parts per trillion "ppt” one gram of solute for every 1012 grams of solution (1 pg/g, 1 ng/kg).equivalent to:1 gram of ink in Blackstrap Lake.1 second in years
82Parts per.... Parts per quadrillion (ppq) one gram of solute for every 1015 grams of solution (1 fg/g, 1 pg/kg).equivalent to:1 gram of ink in Lake Ontario.1 second in 31 million yearsVery few analytical techniques can measure with this degree of accuracyit is still used in some mathematical models of toxicology and epidemiology.
84DilutionThe stock solution is a more concentrated form of solution (hydrochloric acid is 12.4 mol/L).use the chemicals in the lab in diluted form.need to decide how much of the stock solution needed to make the solution you want.
85Dilution Have: 12.4 mol/L stock solution HCl Want: L of mol/L solution.First: Calculate the number of moles in the dilute solution:n = c v= (0.100 mol/L)(2.00 L)= mol
86Dilution Second: Calculate volume of stock solution needed: v = n = molc mol/L= L (1000 mL/L)= mL HCl16.1 mL HCl stock solution is added to water to make 2.00 L of a mol/L solution.
87Dilution There is an easier way to do this: Moles taken from the stock solution (ns) equals the number of moles that goes into the dilute solution (nd)ns = ndandns = csvsnd = cdvdso the formula for dilution is:csvs = cdvd
88DilutionWhat volume of concentrated sulfuric acid (18 M) is needed to make 500. mL of 2.00 M dilute solution?CsVs = CdVd(18 mol/L)Vd = (2.00 mol/L)(500. mL)Vd = 56 mL concentrated H2SO4 is needed.
89DilutionWhat is the concentration of dilute solution if 25.0 mL of glacial acetic acid (24.0 mol/L) is added to make 2.00 L of dilute solution?CsVs = CdVd(24.0 mol/L)(25.0 mL) = (Cd)(2.00 L)(1000 mL/1 L)Cd = mol/L acetic acid.
90DilutionWhat volume of a 1.00 mol/L stock solution of aluminum chloride is needed to make 500. mL of 3.0 x 10-4 mol/L solution?CsVs = CdVd(1.00 mol/L)Vd = (3.0 x 10-4 mol/L)(500. mL)Vd = mL AlCl3 stock solution is needed.
94Mixing Solutionstake 300. mL of the CaCl2 and 200. mL of the Mg3(PO4)2 and we mix them.Assuming that no precipitate is formed, what will the concentration of each ion in solution be after mixing ?
95Mixing Solutions we use the dilution formula: CsVs = CdVd Cs and Vs is the original concentration and volume of each ion0.25 mol/L and 300. mL for the Ca2+Vd is the total volume of the mixture300. mL mL.We are looking for Cd, the ion concentration after mixing:
96Mixing Solutions Cd = CsVs Vd For the Ca2+ ion the calculation is as follows:[Ca2+] = (0.25mol/L)(300.mL) (300. mL mL)= 0.15 mol/L
97Mixing Solutions [Cl1-] = (0.50 mol/L)(300. mL) (300. mL + 200. mL) [Mg2+] = (0.033 mol/L)(200. mL) (300. mL mL)= mol/L[PO43-] = (0.022 mol/L)(200. mL) (300. mL mL)= mol/L
100Consider this problem: 150. mL of mol/L lead (II) nitrate is added to a solution containing sufficient potassium iodide. What mass of lead (II) iodide will precipitate ? Assume the lead (II) iodide is completely insoluble.
101Step 1 Write and balance the chemical equation: Pb(NO3)2 (aq) + 2 KI(aq) PbI2 (s) + 2 KNO3 (aq)
102Step 2 List information: Pb(NO3)2 (aq) + 2 KI(aq) PbI2 (s) + 2 KNO3 (aq)150. mL g ?0.500 mol/L
103Step 3 Convert given information to moles: Pb(NO3)2 (aq) + 2 KI(aq) PbI2 (s) + 2 KNO3 (aq)150. mL g ?0.500 mol/L(0.500 mol/L) (150. mL)(1 L / 1000 mL)= mol
104Step 4 Use mole ratio to find moles of unknown: mol Pb(NO3)2 x mol PbI21 mol Pb(NO3)2= mol PbI2
105Step 5 Convert answer to desired units mol Pb(NO3)2 x mol PbI21 mol Pb(NO3)2= mol PbI2mol PbI2 x ( (126.90)) g/mol= 34.6 g PbI2
106Aqueous cadmium chloride reacts with sodium sulfide to produce bright-yellow cadmium sulfide. What mass of cadmium sulfide would be produced if mL of a 3.91 M solution of sodium sulfide reacts with sufficient cadmium chloride?
107Solutions of calcium nitrate and sodium phosphate react Solutions of calcium nitrate and sodium phosphate react. If 256 mL of a M solution of calcium nitrate reacts with sufficient sodium phosphate, what mass of precipitate would result?
108TitrationThe analytical technique in which one can calculate the concentration of a solute in a solution.is most often done in connection with acid – base reactions.one substance, of unknown concentration and known volume is placed in a flask.the other substance of known concentration is placed in a burette. This allows the volume to be read easily.
110Titration We are dealing with substances in solution. The moles of base is equal to:nb = cbVband the moles of acid in solution is equal to:na = caVaSince at the point of neutralization the moles of acid and base are equal, the following formula is arrived at:caVa = cbVb
111caVa = cbVbWhat is the concentration of HCl if mL of HCl solution is neutralized by mL of M NaOH ?Ca = ?Va = mLCb = mol/LVb = mLCa = (0.100 mol/L)(16.15 mL)50.00 mL= M NaOH
112caVa = cbVbWhat volume of mol/L KOH will be neutralized by 160. mL of mol/L HNO3 ?Ca = mol/LVa = mLCb = mol/LVb = ?Vb = (0.400 mol/L)(160. mL)0.250 mol/L= 256 mL KOH
114Indicators chemicals which are pH sensitive. undergo a colour change as the pH shifts from acid to basic conditions.The neutralization point is detected when the solution changes colour.Indicators are the method of choice in student labs. They are also used in the field, where instrumentation is limited.Indicators are used in acid-base reactions and a broad range of chemical reactions, including redox reactions
116Figure: 17-07Title:Methyl red indicator.Caption:Change in appearance of a solution containing methyl red indicator in the pH range 4.2 to 6.3. The characteristic acidic color is shown in (a), and the characteristic basic color in (b).
117Figure: 17-06Title:Adding a strong base to a strong acid.Caption:The pH curve for titration of mL of a M solution of a strong acid with a M solution of a strong base. In this case the acid is HCl and the base is NaOH. The pH starts out at a low value characteristic of the acid and then increases as base is added, rising rapidly at the equivalence point. Both phenolphthalein and methyl red change color at the equivalence point. (For clarity, water molecules have been omitted from the molecular art.)