1 Ch 5. Reactions of Ions and Molecules in Aqueous Solutions Brady & Senese 5 th Ed.

2 Link to Sections 4.1. Special terminology applies to solutions 4.2. Ionic compounds conduct electricity when dissolved in water 4.3. Acids and bases are classes of compounds with special properties 4.4. Naming acids and bases follows a system 4.5. Ionic reactions can often be predicted 4.6. The composition of a solution is described by its concentration 4.7. Molarity is used for problems in solution stoichiometry 4.8. Chemical analysis and titration are applications of solution stoichiometry

4.1. Special terminology applies to solutions3 Solutions solution –a homogeneous mixture in which the two or more components mix freely solvent - the component present in the largest amount solute – the substance dissolved in the solvent. The solution is named by the solute. concentration - a solute-to-solvent or solute-to- solution ratio describing the composition of the mixture

4.1. Special terminology applies to solutions4 The dilute solution on the left has less solute per unit volume than the (more) concentrated solution on the right Relative concentration terms

4.1. Special terminology applies to solutions5 saturated –no more solute can be dissolved at the current temperature in the given amount of solvent solubility - the amount of solute that can dissolve in the specified amount of solvent at a given temperature (usually g solute/ 100 g solvent or moles solute/L solution) unsaturated - contains less solute than the solubility allows supersaturated- contains more solute than solubility predicts Solubility

4.1. Special terminology applies to solutions6 Most solid solutes are more soluble at higher temperatures. Careful cooling of saturated solutions may result in a supersaturated solution often form a precipitate (ppt.) Supersaturated solutions are unstable

4.2 Ionic Compounds Conduct Electricity When Dissolved in Water7 Ionic compounds in water Water molecules arrange themselves around the ions and dissociate them from the lattice. The separated ions are “hydrated” and conduct electrical current (act as electrolytes) Polyatomic ions remain intact in the dissociation process.

4.2. Ionic compounds conduct electricity when dissolved in water8 Molecular compounds in water The solute particles are surrounded by the water, but the molecules are not dissociated

4.2. Ionic compounds conduct electricity when dissolved in water9 Electrical conductivity Strong electrolyte – aqueous solution that conducts electricity because solute is 100% dissociated into ions Weak electrolyte –aqueous solution that weakly conducts electricity due to low ionization Non-electrolyte – an aqueous solution that doesn’t conduct electricity because solute does not dissociate into ions

4.2. Ionic compounds conduct electricity when dissolved in water10 Ionic equations show dissociated ions hydrated ions, with the symbol (aq), are written separately Na 2 SO 4(s) → 2Na + (aq) + SO 4 2- (aq) you might encounter the equation as: Na 2 SO 4(s) → 2Na + + SO 4 2-  Accepted because only 2 states allow for dissociated ions (plasma and aqueous). Aqueous is far more common  It is vague and not preferred

4.2. Ionic compounds conduct electricity when dissolved in water11 Learning check Write the equations that illustrate the dissociation of the following: Na 3 PO 4(aq) → Al 2 (SO 4 ) 3(aq) → CaCl 2(aq) → Ca(MnO 4 ) 2(aq) → 2Al 3+ (aq) + 3SO 4 2- (aq) 3Na + (aq) + PO 4 3- (aq) Ca 2+ (aq) + 2Cl - (aq) Ca 2+ (aq) + 2MnO 4 - (aq)

4.2. Ionic compounds conduct electricity when dissolved in water12 Your turn! How many ions form on the dissociation of Na 3 PO 4 ? a)1 b)2 c)3 d)4 e)none of the above

4.2. Ionic compounds conduct electricity when dissolved in water13 Writing chemical equations Molecular equation:  Balanced, shows states, all substances electrically neutral  AgNO 3(aq) + KCl (aq) →AgCl (s) + KNO 3(aq) Ionic equation:  Balanced, shows states, shows strong electrolytes as dissociated ions, net charges balance  Ag + (aq) + NO 3 - (aq) + K + (aq) + Cl - (aq) →AgCl (s) + K + (aq) + NO 3 - (aq) Net ionic equation:  Balanced, shows states, eliminates spectator ions from the ionic equation, net charges balance  Ag + (aq) + Cl - (aq) →AgCl (s)

4.2. Ionic compounds conduct electricity when dissolved in water14 Learning check: Write the ionic equations for each: BaCl 2(aq) + Pb(NO 3 ) 2(aq) →PbCl 2(s) + Ba(NO 3 ) 2(aq) Ba 2+ (aq) + 2Cl - (aq) + Pb 2+ (aq) + 2NO 3 - (aq) →PbCl 2(s) + Ba 2+ (aq) + 2NO 3 - (aq) Na 2 CO 3(aq) +CaCl 2(aq) →CaCO 3(s) +2NaCl (aq) 2Na + (aq) + 2CO 3 2- (aq) + Ca 2+ (aq) + 2Cl - (aq) → CaCO 3(s) + 2Na + (aq) + 2Cl - (aq)

4.2. Ionic compounds conduct electricity when dissolved in water15 Writing net ionic equations Show only those ions that were changed by the process Omits spectator ions:  When we compare the reactant to product spectator ions are those ions that are not changed in any way

4.2. Ionic compounds conduct electricity when dissolved in water16 Learning check: Write the following as net ionic equations: Pb 2+ (aq) + 2NO 3 - (aq) + 2K + (aq) + 2I - (aq) →PbI 2(s) + 2K + (aq) + 2NO 3 - (aq) Ba 2+ (aq) + 2Cl - (aq) + 2Na + (aq) + SO 4 2- (aq) → BaSO 4(s) + 2Na + (aq) ) + 2Cl - (aq) 2Na + (aq) ) + 2Cl - (aq) + Hg 2 2+ (aq) + 2NO 3 - (aq) → 2Na + (aq) + 2NO 3 - (aq) + Hg 2 Cl 2(s) 2Cl - (aq) + Hg 2 2+ (aq) → Hg 2 Cl 2(s) Ba 2+ (aq) + SO 4 2- (aq) → BaSO 4(s) Pb 2+ (aq) + 2I - (aq) → PbI 2(s)

4.3.Acids and bases are classes of compounds with special properties17 An acid is a substance that ionizes in a reaction with water to form the hydronium ion, H 3 O + Strong acids are 100% ionized when dissolved, whereas weak acids are far less efficiently ionized The Arrhenius definition of acids

4.3.Acids and bases are classes of compounds with special properties18 It is common to encounter the hydrogen ion (H + ) instead of the hydronium ion The previous ionization is, for simplicity, also written as: H + does not ever exist in aqueous solution- it is always attached to a water molecule as the hydronium ion What is H (aq) + ?

4.3.Acids and bases are classes of compounds with special properties19 Nonmetal oxides can be acids Nonmetal oxides, or “acidic anhydrides” react with water to form acid solutions SO 2(g) + H 2 O (l) →H 2 SO 3(aq) CO 2(g) + H 2 O (l) →H 2 CO 3(aq)

4.3.Acids and bases are classes of compounds with special properties20 Arrhenius bases Base- substance that produces hydroxide ions in water Molecular bases undergo an ionization (hydrolysis) reaction to form the hydroxide ions, and are weak bases Many N-compounds are molecular bases  B (aq) + H 2 O (l) HB + (aq) + OH - (aq)

4.3.Acids and bases are classes of compounds with special properties21 Metal oxides and hydroxides are bases Metal hydroxide solutions dissociate into metal and hydroxide ions and are strong bases. NaOH(s)→Na + (aq) + OH - (aq) Soluble metal oxides “basic anhydrides” react with water to form metal hydroxides that are strong bases CaO (s) +H 2 O (l) → Ca 2+ (aq) + 2OH - (aq)

4.3.Acids and bases are classes of compounds with special properties22 Strong vs. weak Some acids ionize 100% in water, and are termed “strong acids” and are also “strong electrolytes”  HCl, HClO 4, HNO 3, HBr, HI, H 2 SO 4 The very soluble metal hydroxides are strong electrolytes and “strong bases”.  Group IA hydroxides/oxides and Ca, Ba, and Sr hydroxides/oxides.

4.3.Acids and bases are classes of compounds with special properties23 Weak acids and bases are weak electrolytes

4.4. Naming acids and bases follows a system24 Naming binary acids (aqueous) prefix hydro- + nonmetal stem + the suffix –ic, followed by the word acid Stem is first syllable of element name. i.e. Chlorine P and S stems use 2 syllables phosphorus, sulfur the name of the (aq) form differs from other states due to the ionization that occurs in water Molecular compoundAqueous Binary Acid HCl (g) hydrogen chlorideHCl (aq) hydrochloric acid H 2 S (g) hydrogen sulfideH 2 S (aq) hydrosulfuric acid

4.4. Naming acids and bases follows a system25 Oxoacids (aqueous) named according to the anion suffix  anion ends in -ite, the acid name is -ous acid  ends in -ate, the acid name is -ic acid -ate anion acids-ite anion acids HNO 3(aq) nitric acidHClO 2(aq) chlorous acid H 2 SO 4(aq) sulfuric acidH 2 PO 3(aq) phosphorous acid

4.3.Acids and bases are classes of compounds with special properties26 Your turn! Which of the following is the correct name for H 2 SO 3(aq) ? sulfuric acid sulfurous acid hydrosulfuric acid none of the above

4.5. Ionic reactions can often be predicted27 A reaction will exist if… A precipitate (insoluble product) forms from soluble reactants An acid reacts with a base A weak electrolyte product is formed from strong electrolyte reactants A gas is formed from a mixture of reactions

4.5. Ionic reactions can often be predicted28 Metathesis (double replacement) reactions AB + CD → AD + CB Cations change partners Charges on each ion don’t change Formulas of the products are determined by the charges of the reactant ions Metathesis reactions occur only if they form a weak electrolyte or non-electrolyte as a product (otherwise, all ions are spectator ions)

4.5. Ionic reactions can often be predicted29 Predicting metathesis reactions Identify the ions involved:  Do not confuse counting subscripts (those present only to make charges cancel) with those that are characteristic of a polyatomic ion Swap partners and make neutral with appropriate subscripts Assign states using solubility rules Balance the equation HCl (aq) + Ca(OH) 2(aq) → ions: H +, Cl - Ca 2+, OH - counting subscript CaCl 2 + H 2 O (aq) (l) 2 2

4.5. Ionic reactions can often be predicted30 Solubility rules: soluble compounds A general idea as to whether a fair amount of solid will dissolve is achieved using solubility rules 1.All compounds of the alkali metals (Group IA) 2.All salts containing NH 4 +, NO 3 −, ClO 4 −, ClO 3 −, and C 2 H 3 O 2 − 3.All chlorides, bromides, and iodides (salts containing Cl −, Br −, or I − ) except when combined with Ag +, Pb 2+, and Hg All sulfates (salts containing SO 4 2− ) except those of Pb 2+, Ca 2+, Sr 2+, Hg 2 2+, and Ba 2+

4.5. Ionic reactions can often be predicted31 Solubility rules: insoluble compounds 5. All metal hydroxides (ionic compounds containing OH − ) and all metal oxides (ionic compounds containing O 2− ) are insoluble except those of Group IA and of Ca 2+, Sr 2+, and Ba 2+ When metal oxides dissolve, they react with water to form hydroxides. The oxide ion, O 2−, does not exist in water. For example, Na 2 O (s) +H 2 O (l) → 2NaOH (aq) 6.All salts that contain PO 4 3−, CO 3 2−, SO 3 2−, and S 2− are insoluble, except those of Group IA and NH 4 +.

4.5. Ionic reactions can often be predicted32 Learning check: Which of the following compounds are expected to be soluble in water? Ca(C 2 H 3 O 2 ) 2 FeCO 3 AgCl Yes No

4.5. Ionic reactions can often be predicted33 Learning Check: Pb(NO 3 ) 2(aq) + Ca(OH) 2(aq) → BaCl 2(aq) + Na 2 CO 3(aq) → Na 3 PO 4(aq) + Hg 2 (NO 3 ) 2(aq) → NaCl (aq) + Ca(NO 3 ) 2(aq) → Pb(OH) 2(s) + Ca(NO 3 ) 2(aq) BaCO 3(s) + NaCl (aq) NaNO 3(aq) + (Hg 2 ) 3 (PO 4 ) 2(s) NR (No reaction) Predict the products of the following:

4.5. Ionic reactions can often be predicted34 Your turn! Which of the following will be the solid product of the reaction of Ca(NO 3 ) 2(aq) + Na 2 CO 3(aq) →? a)CaCO 3 b)NaNO 3 c)Na(NO 3 ) 2 d)Na 2 (NO 3 ) 2 e)None of the above

4.5. Ionic reactions can often be predicted35 Predicting acid-base reactions Neutralization: metathesis reaction in which acid + metal hydroxide or metal oxide forms water and salt  NaOH (aq) + HCl (aq) →H 2 O (l) + NaCl (aq) Acid-base reaction: reaction of weak base and acid transferring a H + ion, driven by the formation of a weaker acid.  HCl (aq) + NH 3(aq) →NH 4 Cl (aq)

4.5. Ionic reactions can often be predicted36 Learning check Determine the molecular, total ionic and net ionic equations Molecular Equation Total Ionic Equation (TIE) Net Ionic Equation (NIE) 2HCl (aq) + Ca(OH) 2(aq) → 2H 2 O (l) + CaCl 2(aq) H + (aq) + OH - (aq) → H 2 O (l) 2H + (aq) +2Cl - (aq) + Ca 2+ (aq) +2OH - (aq) 2H 2 O (l) → + Ca 2+ (aq) + 2Cl - (aq)

4.5. Ionic reactions can often be predicted37 Your turn! Which of the following is not a product of the reaction: NH 3(aq) +HCN (aq) →? a)NH 3 CN (aq) b)NH 4 + (aq) c)CN - (aq) d)None of the above

4.5. Ionic reactions can often be predicted38 Your turn! Which is the net ionic equation for the reaction: NaOH (aq) + HF (aq) →? a)Na + (aq) + OH - (aq) + H + (aq) + F - (aq) →H 2 O (l) + NaF (aq) b)OH - (aq) + H + (aq) →H 2 O (l) c)OH - (aq) + HF (aq) →H 2 O (l) + F - (aq) d)Na + (aq) + OH - (aq) + HF (aq) →H 2 O (l) + NaF (aq) e)None of the above

4.6. The composition of a solution is described by its concentration39 Molar concentrations In solutions, solutes are dispersed in a larger volume Molarity expresses the relationship between the moles of solute and the volume of the solution Molarity (M)=moles solute/L solution  Hence, a 6.0M solution of HCl contains 6.0 mole HCl in a liter of solution

4.6. The composition of a solution is described by its concentration40 Learning check: What is the molarity of a solution created by dissolving 10.2g KNO 3 in enough water to make 350 mL solution? What mass of KNO 3 are found in mL of.0500M KNO 3 solution? MM KNO 3 = g/mol g 0.29 M

4.6. The composition of a solution is described by its concentration41 Your turn! If 10.0 g NaCl ( g/mol) are dissolved in 75.0 mL. What is the molarity? a) M b) 2.28 M c) 7.5 M d) M e) None of the above

4.6. The composition of a solution is described by its concentration42 Dilution Adding solvent to a solution creates a less concentrated solution moles of solute do not change, hence C stock V stock = C new V new  C=concentration  V=volume Using volumetric glassware ensures that the volumes are known precisely

4.6. The composition of a solution is described by its concentration43 Dilution allows molecules more room Adding solvent does not change how many moles of solute are present The total volume does change The concentration of the solution is decreased while the actual amount of solute is unchanged

4.6. The composition of a solution is described by its concentration44 Learning Check What volume of 12.1M HCl are needed to create 250. mL of 3.2 M HCl? 25 mL of 6 M HCl are diluted to 500 mL with water. What is the molarity of the resulting solution ? 0.3 M 66 mL

4.7. Molarity is used for problems in solution stoichiometry45 What volume of 2M HCl is needed to react 25.2 g Na 2 CO 3 (MM= ) completely? How many moles of BaSO 4 will form if 20.0 mL of M BaCl 2 is mixed with 30.0 mL of M MgSO 4 ? BaCl 2(aq) + MgSO 4(aq) →BaSO 4(s) + MgCl 2(aq) Solution stoichiometry mol

4.7. Molarity is used for problems in solution stoichiometry46 Your turn! What mass of Na 2 CO 3 (MM= ) can be neutralized with mL of 3.11 M HCl? a) 53.0 g b) 1.65(10 2 ) g c) 8.24 g d) 4.12 g e) None of these

4.8. Chemical analysis and titration are applications of solution stoichiometry47. Titration Is the controlled addition of one reactant (titrant) to a known quantity of another (titrate) until the reaction is complete Often, an indicator is used to signal the reaction completion Endpoint: the volume of titrant required to complete the reaction

4.8. Chemical analysis and titration are applications of solution stoichiometry48 Titration in practice:

4.8. Chemical analysis and titration are applications of solution stoichiometry49 Solving titration problems Write the balanced equation Calculate the moles of the known component  M ×L = moles or mass/MM=moles Use stoichiometry to determine moles of the unknown Convert moles to desired quantity

4.8. Chemical analysis and titration are applications of solution stoichiometry50 Path for working titration problems

4.8. Chemical analysis and titration are applications of solution stoichiometry51 Learning Check: mL of HCl are titrated with mL of 1.30M Ca(OH) 2. What is the concentration of HCl? 2HCl (aq) + Ca(OH) 2(aq) →CaCl 2(aq) + 2H 2 O (l) 7.80 M HCl

4.8. Chemical analysis and titration are applications of solution stoichiometry52 Learning Check: A sample of metal ore is reacted according to the following reaction: Fe (s) + 2H + (aq) → Fe 2+ (aq) + H 2(g). If mL of 2.3M HCl are used, what mass of Fe was in the ore?