Dr. S. M. Condren Chapter 5 Reactions in Aqueous Solutions

Dr. S. M. Condren Many reactions involve ionic compounds, especially reactions in water aqueous solutions. KMnO 4 in water K + (aq) + MnO 4 - (aq) Reactions in Aqueous Solution

Dr. S. M. Condren An Ionic Compound, CuCl 2, in Water CCR, page 177

Dr. S. M. Condren How do we know ions are present in aqueous solutions? The solutions The solutions conduct electricity! They are called They are called ELECTROLYTES HCl, CuCl 2, and NaCl are. They dissociate completely (or nearly so) into ions. HCl, CuCl 2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions. Aqueous Solutions

Dr. S. M. Condren HCl, CuCl 2, and NaCl are. They dissociate completely (or nearly so) into ions. HCl, CuCl 2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions. Aqueous Solutions

Dr. S. M. Condren Aqueous Solutions Acetic acid ionizes only to a small extent, so it is a. Acetic acid ionizes only to a small extent, so it is a weak electrolyte. CH 3 CO 2 H(aq) ---> CH 3 CO 2 - (aq) + H + (aq)

Dr. S. M. Condren Aqueous Solutions Acetic acid ionizes only to a small extent, so it is a Acetic acid ionizes only to a small extent, so it is a weak electrolyte. CH 3 CO 2 H(aq) ---> CH 3 CO 2 - (aq) + H + (aq)

Dr. S. M. Condren Aqueous Solutions Some compounds dissolve in water but do not conduct electricity. They are called Some compounds dissolve in water but do not conduct electricity. They are called nonelectrolytes. Examples include: sugarethanol ethylene glycol Examples include: sugarethanol ethylene glycol

Dr. S. M. Condren Electrolytes Conduct electricity in solution due to the presence of ions Strong electrolyte – completely ionized in solution Weak electrolyte – partially ionized in solution Non-electrolyte – nonionic solution

Dr. S. M. Condren Solubility Rules 1. All nitrates (NO 3 -1 ) are soluble. 2. All compounds of Group IA metals and the ammonium ion, NH 4 +, are soluble. 3. All chlorides are soluble except: AgCl, Hg 2 Cl 2 and PbCl All sulfates are soluble except: PbSO 4, BaSO 4, and SrSO 4.

Dr. S. M. Condren Solubility Rules 5. All hydroxides (OH -1 )and sulfides (S -2 )are insoluble except those of the Group IA metals and the ammonium ion. 6. All carbonates (CO 3 -2 ) and phosphates (PO 4 -3 ) are insoluble except those of the Group IA metals and the ammonium ion.

Dr. S. M. Condren Net Ionic Equation Balanced Chemical Equation Pb(NO 3 ) 2 + Na 2 SO 4 ---> PbSO 4 + 2NaNO 3 Total Ionic Equation Pb NO Na +1 + SO Na + + 2NO PbSO 4 Net Ionic Equation Pb +2 + SO 4 -2 PbSO 4

Dr. S. M. Condren A solution of Ba(NO 3 ) 2 is added to a solution of Na 2 SO 4 to make a precipitate. From a table of solubility rules, the product is barium sulfate, sodium nitrate

Dr. S. M. Condren Types of Reactions synthesis reactions or combination reactions decomposition reactions precipitation reactions neutralization reactions –acid –base oxidation-reduction reaction

Dr. S. M. Condren Synthesis or Combination Reactions Formation of a compound from simpler compounds or elements. 2Na (s) + Cl 2(g) 2 NaCl (s)

Dr. S. M. Condren Decomposition Reactions Separation into constituents by chemical reaction. catalysis 2 H 2 O 2 (aq) 2H 2 O (l) + O 2(g)

Dr. S. M. Condren Precipitation Reactions The process of separating a substance from a solution as a solid. AgNO 3 + NaCl ---> AgCl + NaNO 3 precipitate Total Ionic Equation Ag +1 (aq) + NO 3(aq) -1 + Na (aq) +1 + Cl (aq) -1 AgCl (s) + NO 3(aq) -1 + Na (aq) +1 Net Ionic Equation Ag +1 (aq) + Cl (aq) -1 AgCl (s)

Dr. S. M. Condren Neutralization Reactions acid + base ---> salt + water Balanced Chemical Equation HCl + NaOH ---> NaCl + H 2 O Total Ionic Equation H +1 + Cl -1 + Na +1 + OH -1 Na + + Cl -1 + H 2 O Net Ionic Equation H +1 + OH -1 H 2 O

Dr. S. M. Condren Neutralization Reactions acid + base ---> salt + water Balanced Chemical Equation H 2 SO 4 + 2KOH ---> K 2 SO 4 + 2H 2 O Total Ionic Equation 2H + + SO K + + 2OH -1 2H 2 O + SO K + Net Ionic Equation 2H OH -1 2H 2 O

Dr. S. M. Condren Neutralization Reactions acid base salt Household acids and Bases

Dr. S. M. Condren Neutralization Reactions acid –Any of a large class of sour-tasting substances whose aqueous solutions are capable of turning blue litmus indicators red, of reacting with and dissolving certain metals to form salts, and of reacting with bases or alkalis to form salts. –Substance that donates H + ions to solution

Dr. S. M. Condren An acid > H + in water Some strong acids are HClhydrochloric H 2 SO 4 sulfuric HClO 4 perchloric HNO 3 nitric HNO 3 ACIDS

Dr. S. M. Condren WEAK ACIDS = weak electrolytes CH 3 CO 2 Hacetic acid H 2 CO 3 carbonic acid H 3 PO 4 phosphoric acid HFhydrofluoric acid Acetic acid Weak Acids

Dr. S. M. Condren Nonmetal oxides can be acids CO 2 (aq) + H 2 O(liq) ---> H 2 CO 3 (aq) SO 3 (aq) + H 2 O(liq) ---> H 2 SO 4 (aq) and can come from burning coal and oil. ACIDS

Dr. S. M. Condren Neutralization Reactions base –Any of a large class of compounds, including the hydroxides and oxides of metals, having a bitter taste, a slippery solution, the ability to turn litmus blue, and the ability to react with acids to form salts. –Substance that donates a OH -1 ion to solution

Dr. S. M. Condren Base ---> OH - in water NaOH (aq) Na + (aq) + OH - (aq) NaOH is a strong base BASES

Dr. S. M. Condren Ammonia, NH 3 An Important Base

Dr. S. M. Condren Neutralization Reactions salt –The term salt is also applied to substances produced by the reaction of an acid with a base, known as a neutralization reaction. –Salts are characterized by ionic bonds, relatively high melting points, electrical conductivity when melted or when in solution, and a crystalline structure when in the solid state.

Dr. S. M. Condren pH pH = - log [H 3 O + ] [H 3 O + ] = -antilog pH = 10 -pH For log problems, only decimal places are significant, and all decimal places count

Dr. S. M. Condren Example: What is the pH of a 1.0 M solution of HCl? pH = - log [H 3 O + ] [H 3 O + ] = M HCl = 1.0 M because it is a strong electrolyte pH = -log(1.0) = significant figures

Dr. S. M. Condren Example: What is the pH of a 1.0 M solution of HCl? pH = - log [H 3 O + ] [H 3 O + ] = M HCl = 1.0 M because it is a strong electrolyte pH = -log(1.0) = SF

Dr. S. M. Condren Example: What is the pH of a M solution of HCl? pH = - log [H 3 O + ] [H 3 O + ] = M HCl = M because it is a strong electrolyte pH = -log(0.010) = SF

Dr. S. M. Condren Example: What is the pH of a 2.0 M solution of HCl? pH = - log [H 3 O + ] [H 3 O + ] = M HCl = 2.0 M because it is a strong electrolyte pH = -log(2.0) = SF

Dr. S. M. Condren Example: What is the [H 3 O + ] of a solution that has a pH = 2.30? [H 3 O + ] = -antilog pH = 10 -pH [H 3 O + ] = 10 -pH = = 5.0x10 -3 M 2 SF decimal point pacement

Dr. S. M. Condren pH Scale

Dr. S. M. Condren Indicators

Dr. S. M. Condren Oxidation-Reduction Reaction Oxidation - loss of electrons Reduction - gain of electrons Redox reaction oxidizing agent - substance that causes oxidation reducing agent - substance that cause reduction

Dr. S. M. Condren Identify the oxidizing agent in the reaction: 2Al (s) + 6 H + ==> 2 Al 3+ (aq) + 3 H 2(g) Al, H +, Al 3+, H 2 Identify the oxidizing agent in the reaction:

Dr. S. M. Condren Redox Reactions CuSO 4(aq) + Zn (s) Cu (s) + ZnSO 4(aq) 4 Al (s) + 3 O 2(g) 2 Al 2 O 3(s) 2HgO (s) 2 Hg (l) + O 2(g) 2 Al (s) + 3 Br 2 (l) Al 2 Br 6 (s) Fe 2 O 3(s) + 2 Al (s) 2 Fe (l) + Al 2 O 3(s)

Dr. S. M. Condren Solution Solutions, in chemistry, homogeneous mixtures of two or more substances.

Dr. S. M. Condren Solute The substance that is present in smallest quantity is said to be dissolved and is called the solute. The solute can be either a gas, a liquid, or a solid.

Dr. S. M. Condren Solvent The substance present in largest quantity usually is called the solvent. The solvent can be either a liquid or a solid.

Dr. S. M. Condren Preparing a Solution

Dr. S. M. Condren Preparing a Solution by Dilution

Dr. S. M. Condren Molarity The number of moles of solute per liter of solution. molarity => M moles of solute M = liter of solution units => molar = moles/liter = M

Dr. S. M. Condren Example: A sample of NaNO 3 weighing 0.38g is placed in a 50.0-mL volumetric flask. The flask is then filled with water to the mark on the neck, dissolving the solid. What is the molarity of the resulting solution? M = (0.38g NaNO 3 ) (50.0-mL soln) = mol/L = molar= M

Dr. S. M. Condren Stoichiometric Roadmap Grams of A Moles of A Moles of B Grams of B mol A x (mol B / mol A) Multiply by the stoichiometric factor mol B x (g B / mol B) Multiply by the molar mass Volume solution B g B x (mol A / g A) Divide by the molar mass Volume solution A Vol A x (mol A / L A) Multiply by molarity Mol B x (L B / mol B) Diviide by molarity

Dr. S. M. Condren Example: What mass of Na 2 CO 3, in grams, is required for complete reaction with 50.0mL of M HNO 3 ? Na 2 CO 3(aq) + 2 HNO 3(aq) 2 NaNO `3(aq) + CO 2(g) + H 2 O (l) #g Na 2 CO 3 =(50.0 mL) = g Na 2 CO 3

Dr. S. M. Condren EXAMPLE: Lye, which is sodium hydroxide, can be neutralized by sulfuric acid. How many milliliters of M H 2 SO 4 are needed to react completely with 25.0 mL of M NaOH? 2 NaOH (aq) + H 2 SO 4(aq) -----> Na 2 SO 4(aq) + 2 H 2 O (25.0 mL NaOH) #mL H 2 SO 4 = (0.400 mol NaOH) (1 L NaOH) (1 L) (1000 mL) (1 mol H 2 SO 4 ) (2 mol NaOH) (1000 mL H 2 SO 4 ) (0.200 mol H 2 SO 4 ) = 25.0 mL H 2 SO 4