Slide 1 / 33 Slide 2 / 33 New Jersey Center for Teaching and Learning AP Chemistry Progressive Science Initiative This material is made freely available at www.njctl.org and is intended for the non-commercial use of students and teachers. These materials may not be used for any commercial purpose without the written Unit 3: Presentation D permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to Acids and Bases make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course materials to parents, students and others. Click to go to website: www.njctl.org www.njctl.org Slide 3 / 33 Slide 4 / 33 Acid/Base Reactions Acid and Base Definitions The most widely used definition of acids and bases in the Bronsted- Lowry definition. ACID BASE H + Donor H + acceptor NH 4+(aq) + H 2 O (l) --> NH 3(g) + H 3 O +(aq) Acid: Base: CaCO 3(s) + 2H +(aq) --> H 2 O (l) + CO 2(g) + Ca 2+(aq) H + Donor H + Acceptor Caves are formed by the acid/base reaction of limestone with acid which causes the limestone rock to dissolve away. Slide 5 / 33 Slide 6 / 33 Conjugate Acids and Bases Conjugate Acids and Bases After an acid donates an H+ ion, the resulting species can always CN -(aq) --> HCN (aq) behave as a base and grab the H+ back again. Predicting the base Conj. acid formula of a NH 4+(aq) + H 2 O <--> NH 3(g) + H 3 O +(aq) conjugate acid or HCO 3-(aq) --> CO 32-(aq) base involves Base: acid Acid: Conj. base writing the formula of the species H + Acceptor H + Donor CH 3 NH 2(aq) --> CH 3 NH 3+(aq) produced after the base Conj. acid donation or Therefore, NH 3 acts as the conjugate base of NH 4+ and H 3 O + acceptance of an acts as the conjugate acid of H 2 O. CH 3 COOH (aq) --> CH 3 COO -(aq) H+ ion. Conj. base acid NH 4+(aq) + H 2 O (l) <--> NH 3(g) + H 3 O +(aq)
Slide 7 / 33 Slide 8 / 33 Amphoteric Molecules Amphoteric Molecules Amphoteric molecules can behave as either acids or bases Common amphoteric molecules are the conjugate bases of diprotic or depending on their environment. polyprotic acids H 2 C 2 O 4(aq) HC 2 O 4-(aq) C 2 O 42-(aq) Water is a classic example Acid Amphoteric Base H 2 O donates H + accepts H + H 3 PO 4(aq) H 2 PO 4-(aq) HPO 42-(aq) PO 43-(aq) H 3 O + OH - Conj. acid Conj. base Acid Amphoteric Amphoteric Base Whether water acts as an acid or base will depend on the relative "strength" of other acids or bases it is reacted with. Slide 9 / 33 Slide 9 (Answer) / 33 1 Which of the following is NOT an acid/base reaction? 1 Which of the following is NOT an acid/base reaction? A HCN (aq) + H 2 O (l) --> CN -(aq) + H 3 O +(aq) A HCN (aq) + H 2 O (l) --> CN -(aq) + H 3 O +(aq) B NH 3(aq) + HC 2 H 3 O 2(aq) --> NH 4+(aq) + C 2 H 3 O 2-(aq) B NH 3(aq) + HC 2 H 3 O 2(aq) --> NH 4+(aq) + C 2 H 3 O 2-(aq) C H +(aq) + H 2 O (l) --> H 3 O +(aq) C H +(aq) + H 2 O (l) --> H 3 O +(aq) Answer D Pb 2+(aq) + 2I -(aq) --> PbI 2(s) D Pb 2+(aq) + 2I -(aq) --> PbI 2(s) D E All are acid/base reactions E All are acid/base reactions [This object is a pull tab] Slide 10 / 33 Slide 10 (Answer) / 33 2 In which of the following reactions does the underlined 2 In which of the following reactions does the underlined substance behave as an acid? substance behave as an acid? I. CH 3 NH 2(g) + H 2 O (l) --> CH 3 NH 3+(aq) + OH -(aq) I. CH 3 NH 2(g) + H 2 O (l) --> CH 3 NH 3+(aq) + OH -(aq) A I only A I only II. HCOOH (aq) + NH 2-(aq) --> HCOO -(aq) + NH 3(aq) II. HCOOH (aq) + NH 2-(aq) --> HCOO -(aq) + NH 3(aq) III. HClO (aq) + OH- (aq) --> ClO -(aq) + H 2 O (l) III. HClO (aq) + OH- (aq) --> ClO -(aq) + H 2 O (l) B II only B II only C III only C III only Answer D D II and III only D II and III only E I, II, and III E I, II, and III [This object is a pull tab]
Slide 11 / 33 Slide 11 (Answer) / 33 3 What would be the expected products of the following 3 What would be the expected products of the following reaction... reaction... H 2 PO 4-(aq) + OH -(aq) --> ____________ H 2 PO 4-(aq) + OH -(aq) --> ____________ A H 3 PO 4(aq) + H 2 O (l) A H 3 PO 4(aq) + H 2 O (l) B H 2 PO 42-(aq) + H 2 O (l) B H 2 PO 42-(aq) + H 2 O (l) Answer D C HPO 4-(aq) + H 3 O +(aq) C HPO 4-(aq) + H 3 O +(aq) D HPO 42-(aq) + H 2 O (l) D HPO 42-(aq) + H 2 O (l) E None of these E None of these [This object is a pull tab] Slide 12 / 33 Slide 12 (Answer) / 33 4 Which of the following is the conjugate acid of the chlorite 4 Which of the following is the conjugate acid of the chlorite ion (ClO 2 -)? ion (ClO 2 -)? A HClO 2 A HClO 2 Answer B HClO 2+ B HClO 2+ A C HClO C HClO D HClO 3 D HClO 3 [This object is a pull tab] E HClO 2- E HClO 2- Slide 13 / 33 Slide 13 (Answer) / 33 5 Which of the following has the acid paired with it's 5 Which of the following has the acid paired with it's appropriate conjugate base? appropriate conjugate base? I. HPO 42-(aq) /PO 42-(aq) I. HPO 42-(aq) /PO 42-(aq) A I only A I only II. HBrO 2(aq) /BrO -(aq) II. HBrO 2(aq) /BrO -(aq) B II only III. H 2 CrO 4(aq) /HCrO 4-(aq) B II only III. H 2 CrO 4(aq) /HCrO 4-(aq) Answer C III only C III only C D I and III only D I and III only E I and II only E I and II only [This object is a pull tab]
Slide 14 / 33 Slide 14 (Answer) / 33 6 Which of the following would be amphoteric? 6 Which of the following would be amphoteric? A CO 32-(aq) A CO 32-(aq) B HC 2 H 3 O 2(aq) B HC 2 H 3 O 2(aq) Answer C C HC 2 O 4-(aq) C HC 2 O 4-(aq) D F -(aq) D F -(aq) [This object is a pull tab] E H 3 O +(aq) E H 3 O +(aq) Slide 15 / 33 Slide 16 / 33 Strong Acids Strong Acids Strong acids dissociate 100% in aqueous solutions thereby donating Conjugate bases of strong acids are not able to accept H+ ions back ALL of their H+ ions. and therefore do not participate in acid/base reactions. Therefore, much like a soluble ionic compound, any strong acid must be written as being broken up into it's ions. H +(aq) + NO 3-(aq) + NH 3(aq) --> NH 4+(aq) H +(aq) + NH 3(aq) --> NH 4+(aq) Strong Acid Written as... HCl (aq) H +(aq) + Cl -(aq) H +(aq) + Br -(aq) + ClO -(aq) --> HClO (aq) HNO 3(aq) H +(aq) + NO 3-(aq) H +(aq) + ClO -(aq) --> HClO (aq) H 2 SO 4(aq) 2H +(aq) + SO 42-(aq) HClO 4(aq) H +(aq) + ClO 4-(aq) HBr (aq) H +(aq) + Br -(aq) HI (aq) H +(aq) + I -(aq) Slide 17 / 33 Slide 18 / 33 Writing Acid/Base Reactions 7 Which of the following species would be an extremely weak base? First write the correct formulas for all species involved, breaking compounds into ions if soluble ionics or strong acids. A Br - Example: Aqueous solutions of methlyamine (CH3NH2) and B F - hydroiodic acid are mixed. CH 3 NH 2(aq) + H +(aq) + I -(aq) --> C NO 2- Predict products based on acid/base principles. D ClO 3- E NH 3 CH 3 NH 2(aq) + H +(aq) + I -(aq) --> CH 3 NH 3+(aq) CH 3 NH 2(aq) + H +(aq) --> CH 3 NH 3+(aq)
Slide 18 (Answer) / 33 Slide 19 / 33 7 Which of the following species would be an extremely 8 Why are strong acids written as separate ions? weak base? A Strong acids are dangerous A Br - B Strong acids have strong conjugate bases Answer B F - A C Strong acids do not have conjugate bases C NO 2- D Strong acids donate all of their H+ ions D ClO 3- [This object is a pull tab] E None of these E NH 3 Slide 19 (Answer) / 33 Slide 20 / 33 8 Why are strong acids written as separate ions? 9 Which of the following is NOT a strong acid? A Strong acids are dangerous A HNO 3 Answer B Strong acids have strong conjugate bases B HF D C Strong acids do not have conjugate bases C HBr D Strong acids donate all of their H+ ions D HClO 4 [This object is a pull tab] E None of these E H 2 SO 4 Slide 20 (Answer) / 33 Slide 21 / 33 9 Which of the following is NOT a strong acid? 10 Which of the following best represents the balanced equation for the acid/base reaction of aqueous potassium hydroxide and chromic acid (H 2 CrO 4 )? A HNO 3 A OH - + H 2 CrO 4 → H 2 O + CrO 42- B HF Answer B 2K + + H 2 CrO 4 → 2H + + K 2 CrO 4 C HBr B C 2OH - + H 2 CrO 4 → 2H 2 O + CrO 42- D HClO 4 D 2K + + H 2 CrO 4 → 2KH + CrO 42- E H 2 SO 4 [This object is a pull tab] E None of these
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