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CHEM 102 Lecture Notes - Lecture 17: Litmus, Amphoterism, Acid Strength

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3 Mar 2017

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Drexel University

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In water, h+ always associates w/ h2o to make h3o (hydronium ion) Acids and bases combine to form h2o, neutralizing the solution. Substance that makes h+ ions in aq solution. Substance that makes oh- ions in aq solution. Concentration of h3o = concentration of strong acid. Ha (aq) h+ (aq) + a- (aq) Produce oh- by accepting a proton from water and ionizing water. Water is amphoteric and can act as an acid or base. Two substances related to eachother by the transfer of a proton. Any base to which a proton has been added. Originally a base but becomes an acid. Any acid to which a proton has been removed. Originally an acid but becomes a base. 3+ 2 4+ . Polarity and strength of bond affect how easily the h is donated. H must be the positive pole to be acidic. Acidity increases right (w/ electronegativity) as bonds become more polar.

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Related Questions

Unlike strong acids and bases that ionize completely in solution, weak acids or bases partially ionize. The tendency to ionize (i.e., the ionic strength) of a weak acid or base can be quantified in several ways including;

Ka or Kb, pKa or pKb, and percent ionization.

Benzoic acid is a weak acid that has antimicrobial properties. Its sodium salt, sodium benzoate, is a preservative found in foods, medications, and personal hygiene products. Benzoic acid dissociates in water:

C6H5COOH(aq)+H2O(l)âC6H5COOâ(aq)+H3Oâ(aq)

The pKa of this reaction is 4.2. In a 0.80 mol Lâ1 solution of benzoic acid, what percentage of the molecules are ionized?

Express your answer to two significant figures and include the appropriate units.

Unlike strong acids and bases that ionize completely in solution, weak acids or bases partially ionize. The tendency to ionize (i.e., the ionic strength) of a weak acid or base can be quantified in several ways including

Ka or Kb,

pKa or pKb,

and percent ionization.

Part A

Pyridine is a weak base that is used in the manufacture of pesticides and plastic resins. It is also a component of cigarette smoke. Pyridine ionizes in water as follows:

C5H5N+H2OâC5H5NH++OHâ

The pKb of pyridine is 8.75. What is the pH of a 0.455 M solution of pyridine?

Express the pH numerically to two decimal places.

pH=____________

Part B

Benzoic acid is a weak acid that has antimicrobial properties. Its sodium salt, sodium benzoate, is a preservative found in foods, medications, and personal hygiene products. Benzoic acid dissociates in water:

C6H5COOHâC6H5COOâ+H+

The pKa of this reaction is 4.2. In a 0.58 M solution of benzoic acid, what percentage of the molecules are ionized?

Express the percentage numerically using two significant figures.

percent ionized = _______________ %

Which of the following is a gas-evolution reaction? 2 C2H6(I) +- 7 O2(g) rightarrow 4 CO2(g) + 6 H2O(g) LiCI(aq) + NaNO3(aq) rightarrow LiNO3(aq) + NaCI(g) 2 H2(g) + O2(g) rightarrow 2 H2O(g) NH4CI(aq) + KOH(aq) rightarrow KCI(aq) + NH3(g) + H2O(l) None of the above are gas-evolution reactions. Which of the following is an acid base reaction? C(s) + O2(g) rightarrow CO2(g) Fe(s) + 2 AgNO3(aq) rightarrow 2 Ag(s) + Fe(NO3)2(aq) 2 HCIO4(aq) + Ca(OH)2(aq) rightarrow 2 H2O(l) + Ca(CIO4)2(aq) OMgSO4(aq) + Ba(NO3)2(aq) - Mg(N03)2(aq) + BaS04(s) None of the above are acid base reactions. Identify the spectator ions in the following molecular equal KBr(aq) + AgNO3(aq) rightarrow AgBr(s) + KNO3(aq) Ag+ and NO3 k+ and NO3- k+ and Br+ Ag+ and Br+ There are no spectator ions in this reaction. Which of the following is a precipitation reaction? HCI(aq) + KOH(aq) rightarrow KCI(aq) + H2O(l) NaCI(aq) + Lil(aq) rightarrow Nal(aq) + LiCI(aq) 2 Lil(aq) + Hg2(NO3)2(aq) rightarrow Hg2l2(s) + 2 LiN03(aq) 2n(s) + 2 AgNO3(aq) rightarrow 2 Ag(s) + Zn(NO3)2(aq) None of the above are precipitation reactions. Give the net ionic equation for the reaction (if any) that occurs when aqueous solutions of H2SO4 and KOH are mixed. H+(aq) + OH-(aq) rightarrow H2O(l) H+(aq) + OH-(aq) + 2 K4(aq) + SO42'(aq) rightarrow H2O(l) + K2SO4(s) H22+(aq) + OH - (aq) rightarrow H2(OH)2(l) 2 K+(aq) + SO42 - rightarrow (aq) K2SO4(s) No reaction occurs. Give the net ionic equation for the reaction (if any) that occurs when aqueous solutions of K2S and Fe(NO3)2 are mixed. Fe2+(aq) + S2-(aq) + 2 K4(aq) + 2 NO3(aq) righarrow FeS(s) + 2 K4(aq) + 2 NO3(aq) Fe2+(aq) + S2 - (aq) + 2 K4(aq) + 2 NO3 - (aq) rightarrow Fe2+(aq) + S2-(aq) + 2 KNO3(s) Fe2+(aq) + S2 - (aq) rightarrow FeS(s) K+(aq) + NO3 - (aq) rightarrow KNO3(s) No reaction occurs. Choose the statement below that is TRUE. The term "weak electrolyte" means that the substance is inert. A strong acid solution consists of only partially ionized acid molecules. A molecular compound that does not ionize in solution is considered a strong electrolyte. A weak acid solution consists of mostly nonionized acid molecules. The term "strong electrolyte" means that the substance is extremely reactive. What is the molarity of a NaOH solution if 48.0 mL of a 0.220 M H2S04 solution is required to neutralize a 25.0-mL sample of the NaOH solution? 00.115 00.845 00.422 00.229 0132 What element is undergoing reduction (if any) in the following reaction? Zn(s) + 2 AgN03(aq) rightarrow Zn(NO3)2(aq) + 2 Ag(s) O Ag Zn N This is not an oxidation-reduction reaction.

Show transcribed image text Which of the following is a gas-evolution reaction? 2 C2H6(I) +- 7 O2(g) rightarrow 4 CO2(g) + 6 H2O(g) LiCI(aq) + NaNO3(aq) rightarrow LiNO3(aq) + NaCI(g) 2 H2(g) + O2(g) rightarrow 2 H2O(g) NH4CI(aq) + KOH(aq) rightarrow KCI(aq) + NH3(g) + H2O(l) None of the above are gas-evolution reactions. Which of the following is an acid base reaction? C(s) + O2(g) rightarrow CO2(g) Fe(s) + 2 AgNO3(aq) rightarrow 2 Ag(s) + Fe(NO3)2(aq) 2 HCIO4(aq) + Ca(OH)2(aq) rightarrow 2 H2O(l) + Ca(CIO4)2(aq) OMgSO4(aq) + Ba(NO3)2(aq) - Mg(N03)2(aq) + BaS04(s) None of the above are acid base reactions. Identify the spectator ions in the following molecular equal KBr(aq) + AgNO3(aq) rightarrow AgBr(s) + KNO3(aq) Ag+ and NO3 k+ and NO3- k+ and Br+ Ag+ and Br+ There are no spectator ions in this reaction. Which of the following is a precipitation reaction? HCI(aq) + KOH(aq) rightarrow KCI(aq) + H2O(l) NaCI(aq) + Lil(aq) rightarrow Nal(aq) + LiCI(aq) 2 Lil(aq) + Hg2(NO3)2(aq) rightarrow Hg2l2(s) + 2 LiN03(aq) 2n(s) + 2 AgNO3(aq) rightarrow 2 Ag(s) + Zn(NO3)2(aq) None of the above are precipitation reactions. Give the net ionic equation for the reaction (if any) that occurs when aqueous solutions of H2SO4 and KOH are mixed. H+(aq) + OH-(aq) rightarrow H2O(l) H+(aq) + OH-(aq) + 2 K4(aq) + SO42'(aq) rightarrow H2O(l) + K2SO4(s) H22+(aq) + OH - (aq) rightarrow H2(OH)2(l) 2 K+(aq) + SO42 - rightarrow (aq) K2SO4(s) No reaction occurs. Give the net ionic equation for the reaction (if any) that occurs when aqueous solutions of K2S and Fe(NO3)2 are mixed. Fe2+(aq) + S2-(aq) + 2 K4(aq) + 2 NO3(aq) righarrow FeS(s) + 2 K4(aq) + 2 NO3(aq) Fe2+(aq) + S2 - (aq) + 2 K4(aq) + 2 NO3 - (aq) rightarrow Fe2+(aq) + S2-(aq) + 2 KNO3(s) Fe2+(aq) + S2 - (aq) rightarrow FeS(s) K+(aq) + NO3 - (aq) rightarrow KNO3(s) No reaction occurs. Choose the statement below that is TRUE. The term "weak electrolyte" means that the substance is inert. A strong acid solution consists of only partially ionized acid molecules. A molecular compound that does not ionize in solution is considered a strong electrolyte. A weak acid solution consists of mostly nonionized acid molecules. The term "strong electrolyte" means that the substance is extremely reactive. What is the molarity of a NaOH solution if 48.0 mL of a 0.220 M H2S04 solution is required to neutralize a 25.0-mL sample of the NaOH solution? 00.115 00.845 00.422 00.229 0132 What element is undergoing reduction (if any) in the following reaction? Zn(s) + 2 AgN03(aq) rightarrow Zn(NO3)2(aq) + 2 Ag(s) O Ag Zn N This is not an oxidation-reduction reaction.