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Chapter 4: Aqueous Reactions Solution: Solvent: substance present in the larger amount Solute: substance(s) dissolved in solvent, generally present in.

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Presentation on theme: "Chapter 4: Aqueous Reactions Solution: Solvent: substance present in the larger amount Solute: substance(s) dissolved in solvent, generally present in."— Presentation transcript:

1 Chapter 4: Aqueous Reactions Solution: Solvent: substance present in the larger amount Solute: substance(s) dissolved in solvent, generally present in lesser amounts than solvent homogeneous mixture of solute and solvent

2 Chapter 4: Aqueous Reactions Ionic Compounds When ionic compounds dissolve in water, they dissociate completely H 2 O NaCl (aq)→Na + (aq)+Cl - (aq)

3 Chapter 4: Aqueous Reactions Molecular Compounds Most molecular compounds do not dissociate in water + H 2 O methanol Methanol dissolved in water

4 Chapter 4: Aqueous Reactions Molecular Compounds Some molecular compounds dissociate (ionize) in water (acids) HCl (aq)→H + (aq) +Cl - (aq) Strong acids, such as hydrochloric acid, dissociate completely: Weak acids, such as acetic acid, dissociate only partially: CH 3 COOH (aq)H + (aq) + CH 3 COO - (aq)

5 Chapter 4: Aqueous Reactions Aqueous solutions that contain ions, conduct electricity Electrolytes: substances that generate ions when dissolved in water ● Ionic compounds ● Strong acids ● Weak acids For example: strong electrolyte weak electrolyte Non-Electrolytes: substances that do not generate ions when dissolved in water ● Strong bases ● Weak bases strong electrolyte weak electrolyte

6 Chapter 4: Aqueous Reactions Strong, Weak, and Non- Electrolytes AgINaCl HCl Ag + I-I- Na + Cl - H+H+ C 12 H 22 O 11 sugar Ionic Molecular (dissociated acid) Molecular Strong electrolyte Non-electrolyte

7 Chapter 4: Aqueous Reactions Formic acid HCOOH HCOO - H+H+ Electrolytes and Non-Electrolyte definition only refers to the molecules/ions that are dissolved If the solution contains any type of ion, it is an electrolyte If all the dissolved particles are ions, the solution is a strong electrolyte If only some of the dissolved particles are ions, the solution is a weak electrolyte Weak electrolyte Molecular Strong, Weak, and Non- Electrolytes

8 Chapter 4: Aqueous Reactions Aqueous solutions that contain ions, conduct electricity Substance Ionic Molecular soluble highly soluble in H 2 O insoluble very little soluble in H 2 O AcidBaseNeither acid nor base strong electrolyte strong electrolyte weakstrong weak strong bases are usually ionic compunds strong electrolyte weak electrolyte weak electrolyte non-electrolyte

9 Chapter 4: Aqueous Reactions Sample 1Sample 2Sample 3

10 Chapter 4: Aqueous Reactions (2) Pb(NO 3 ) 2 (aq)+2 NaI (aq) (1) AgNO 3 (aq) + NaCl (aq) (1)(2) →AgCl (s)+ NaNO 3 (aq) →PbI 2 (s)+2 NaNO 3 (aq) soluble in waterinsoluble in water (precipitate)

11 Chapter 4: Aqueous Reactions Some reactions involving ionic compounds: Exchange or Metathesis Reactions AX+BY→AY+BX

12 Chapter 4: Aqueous Reactions Exchange or Metathesis Reactions If one of the products in insoluble, the reaction is a precipitation reaction: AgNO 3 (aq)+NaCl (aq)→AgCl (s)+NaNO 3 (aq) white precipitate AgNO 3 (aq)+NaI (aq)→ AgI (s)+NaNO 3 (aq) brownish precipitate

13 Chapter 4: Aqueous Reactions Precipitation Reactions AgNO 3 (aq)+NaI (aq)→ AgI (s)+NaNO 3 (aq) brownish precipitate heterogeneous mixture!

14 Chapter 4: Aqueous Reactions Precipitation Reactions Ni(NO 3 ) 2 +NaOH →Ni(OH) 2 +NaNO 3 A: Y: Ni 2+ OH - B: X: Na + NO 3 - II) Exchange X and Y: III) Determine stoichiometry of compounds formed: Ni 2+ + Na + + => Ni(OH) 2 => NaNO 3 IV) Balance equation! 2 V) Is there an insoluble product? (aq) (aq) (s) (aq) Na + OH - I) Identify ions: A: X: B: Y: Ni 2+ NO OH - NO 3 -

15 Chapter 4: Aqueous Reactions Precipitation Reactions Digest of solubility rules: Salts of the following ions are always soluble: ● Group IA metals Li +, Na +, K +... ● Ammonium NH 4 + ● Nitrate NO 3 - ● Acetate C 2 H 3 O 2 - [CH 3 COO -, AcO - ]

16 Chapter 4: Aqueous Reactions Precipitation Reactions How do you know which ionic compounds are soluble?

17 Chapter 4: Aqueous Reactions Precipitation Reactions (NH 4 ) 2 SO 4 AgCl CuSO 4 FeNO 3 Cu(OH) 2 CaCO 3 soluble (NH 4 + salt) soluble (NO 3 - salt) LiClsoluble (Li + salt) insoluble soluble insoluble Ca(C 2 H 3 O 2 ) 2 soluble (C 2 H 3 O 2 - [acetate] salt)

18 Chapter 4: Aqueous Reactions Ni(NO 3 ) 2 (aq) +2 NaOH (aq) →Ni(OH) 2 (s) +2 NaNO 3 (aq) Net Ionic Equations Molecular Equation (shows undissociated compounds): Ionic Equation: Net Ionic Equation: Ni 2+ (aq) + 2 NO 3 - (aq) + 2 Na + (aq) + 2 OH - (aq) → Ni(OH) 2 (s) + 2 Na + (aq) + 2 NO 3 - (aq) Ni 2+ (aq) + 2 OH - (aq) → Ni(OH) 2 (s) spectator ions The spectator ions do not participate in the reaction!

19 Chapter 4: Aqueous Reactions Ca(NO 3 ) 2 (aq) + Na 2 CO 3 (aq) → CaCO 3 (s) + NaNO 3 (aq) 2 Ca 2+ (aq) + CO (aq) → CaCO 3 (s) Spectator ions: 2 Na +, 2 NO 3 - Net ionic equation:

20 Chapter 4: Aqueous Reactions Ca(NO 3 ) 2 (aq) + NaC 2 H 3 O 2 (aq) → Ca(C 2 H 3 O 2 ) 2 + NaNO 3 (aq) 2 2 Spectator ions: ALL ! (aq) If all salts are soluble, no precipitation reaction will take place

21 Chapter 4: Aqueous Reactions Properties of Acids and Bases Acids ● taste sour ● turn blue litmus red ● produce CO 2 when reacting with carbonates ● produce H 2 when reacting with metals ● generate protons, H +, when dissolved in water Bases ● taste bitter ● turn red litmus blue ● generate hydroxide ions, OH -, when dissolved in water

22 Chapter 4: Aqueous Reactions Properties of Acids and Bases Acids ● produce CO 2 when reacting with carbonates

23 Chapter 4: Aqueous Reactions The reaction of acids with carbonate salts: MgCO 3 (s) + HCl (aq) →MgCl 2 (aq) + H 2 CO 3 (aq) 2 H 2 CO 3 (aq) → CO 2 (g) + H 2 O (l) unstable Overall: MgCO 3 (s) + HCl (aq) →MgCl 2 (aq) + CO 2 (g) + H 2 O (l) 2

24 Chapter 4: Aqueous Reactions Which of the following is insoluble? a. (NH 4 )CO 3 b. ZnS c. K 2 CO 3 d. Zn(NO 3 ) 2

25 Chapter 4: Aqueous Reactions Properties of Acids and Bases Strong Acids HClHydrochloric acid HBrHydrobromic acid HIHydroiodic acid HNO 3 Nitric acid H 2 SO 4 Sulfuric acid HClO 3 Chloric acid HClO 4 Perchloric acid when dissolved, dissociate completely in water = strong electrolytes

26 Chapter 4: Aqueous Reactions Properties of Acids and Bases Weak Acids HFHydrofluoric acid CH 3 COOHAcetic acid HCOOHFormic acid... when dissolved, do not dissociate completely in water = weak electrolytes for example:

27 Chapter 4: Aqueous Reactions Properties of Acids and Bases Strong Bases Metal Hydroxides of Group IA metals: NaOH, KOH... Metal Hydroxides of Group IIA metals: Ca(OH) 2, Mg(OH) 2... strong electrolytes

28 Chapter 4: Aqueous Reactions Properties of Acids and Bases Weak Bases NH 3 Ammonia generate few ions when dissolved = weak electrolytes NH 3 (aq) + H 2 O (l) → NH 4 + (aq) + OH - (aq) for example:

29 Chapter 4: Aqueous Reactions Neutralization Reactions HNO 3 (aq) + NaOH (aq) → acidbaseWATERsalt (ionic compound) In a neutralization reaction, an acid and a base react to form water and a salt (ionic compound) net ionic equation: H + (aq) + NO 3 - (aq) + Na + (aq) + OH - (aq) → H 2 O (l) + Na + (aq) + NO 3 - (aq) H + (aq) + OH - (aq) → H 2 O (l) H 2 O (l) + NaNO 3 (aq)

30 Chapter 4: Aqueous Reactions Complete and balance the following neutralization reaction: Sr(OH) 2 (aq) + HBr (aq) →SrBr 2 (aq) + H 2 O (l) 2 2 net ionic equation: Sr 2+ (aq) + 2 OH - (aq) + 2 H + (aq) + 2 Br - (aq) → Sr 2+ (aq) + 2 Br - (aq) + 2 H 2 O (l) net: 2OH - (aq) + 2H + (aq) → 2H 2 O (l) OH - (aq) + H + (aq) → H 2 O (l)

31 What is the net ionic reaction for the reaction between insoluble lead(II) hydroxide and nitric acid? Pb(OH) 2 (s) +2 2 Chapter 4: Aqueous Reactions HNO 3 (aq)→Pb(NO 3 ) 2 (aq) + H2OH2O(l) acidbasewatersalt When writing an ionic equation, which compounds are written in ionic form? a. All compounds in the equation b. Reactants only c. Compounds that generate ions d. Hydroxide ions and protons (aq)

32 What is the net ionic reaction for the reaction between insoluble lead(II) hydroxide and nitric acid? Pb(OH) 2 (s) +2 2 Chapter 4: Aqueous Reactions HNO 3 (aq)→Pb(NO 3 ) 2 (aq) + H2OH2O(l) Pb(OH) 2 (s) + 2 H + (aq) + 2 NO 3 - (aq) → Pb 2+ (aq) + 2 NO 3 - (aq) + 2 H 2 O (l) Pb(OH) 2 (s) + 2 H + (aq) → Pb 2+ (aq) + 2 H 2 O (l) acidbasewatersalt

33 Chapter 4: Aqueous Reactions Concentrations of Solutions... are measured in Molarity Molarity The concentration of 0.4 L of solution containing 0.25 moles of sugar is = 0.6 M

34 Chapter 4: Aqueous Reactions Someone is preparing to cook pasta by adding 5.0 g of table salt (NaCl, 49.5 g/mol) to 400 mL of boiling water. What is the molarity of the resulting NaCl solution? (I) convert g NaCl into mol NaCl: (II) calculate molarity: 5.0 gconcentration (molarity = mol/L)moles MM Volume

35 Chapter 4: Aqueous Reactions How many moles of HF are needed to make 0.15 L of a 0.13M HF solution? x 0.15 L = mol HF 0.13 M (= mol/L) HFmol HF Volume 0.02

36 Chapter 4: Aqueous Reactions Proton Concentration in Aqueous Solutions [H + ] ≡ proton concentrationpH = -log [H+] [H + ] = M[H + ] = M = 1 x MpH = -log(1 x ) = 3 acidicbasicneutral The pH scale [H + ] x [OH - ] = = constant and[H + ] = 10 - pH Neutral solution: [H + ] = [OH - ] = M

37 Chapter 4: Aqueous Reactions What are the proton and hydroxide concentrations in a solution that has a pH of 4.3 ? pH = -log [H + ] -pH = log [H + ] 10 - pH = [H + ] [H + ] = = 5.0 x M [H + ] x [OH - ] = [OH - ] = [H + ] = = 5.0 x x M

38 Chapter 4: Aqueous Reactions Dilutions add solvent number of solute molecules before dilution number of solute molecules after dilution = number of moles of solute before dilution number of moles of solute after dilution =

39 Chapter 4: Aqueous Reactions What is the concentration of a solution that is made by adding 0.3L of water to 15mL of a 0.65M solution? V conc = 15mL = 0.015LM conc = 0.65M V dil = 0.3L + 15mL = 0.3L L = 0.315L Dilution: adding solvent without changing number of moles higher concentrationlower concentration

40 Chapter 4: Aqueous Reactions Solution Stoichiometry and Chemical Analysis What volume of a 0.30 M HCl solution is needed to completely react 3.5 g of Ca(OH) 2 ? HCl (aq) + Ca(OH) 2 (aq) →H 2 O (l) +CaCl 2 (aq) g Ca(OH) 2 → moles Ca(OH) 2 → moles HCl→ Liters HCl molar mass = 74g/molstoichiometric factor from equation molarity of solution Strategy:

41 Solution Stoichiometry and Chemical Analysis What volume of a 0.30 M HCl solution is needed to completely react 3.5 g of Ca(OH) 2 ? HCl (aq) + Ca(OH) 2 (aq) →H 2 O (aq) +CaCl 2 (aq)22 Chapter 4: Aqueous Reactions

42 What is the molarity of Na + ions in a 0.2 M solution of Na 2 SO 4 ? Na 2 SO 4 (aq) → 2 Na + (aq) + SO 4 2- (aq) SO 4 2- Na + SO = 0.4 M Na + molarity Na 2 SO 4 molarity Na + ions empirical formula


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