Slide 1 / 208 Slide 2 / 208 Acids and Bases Slide 3 / 208 Slide 4 / 208 Table of Contents: Acids and Bases Click on the topic to go to that section Properties of Acids and Bases · Properties of Conjugate Acid and Base Pairs · Acids and Bases Amphoteric Substances · Strong Acids and Bases · Auto-Ionization of Water · pH · Weak Acids and Bases · Polyprotic acids · The Relationship Between K a and K b · Return to the Table of contents Acid-Base Properties of Salt Solutions · Factors Affecting Acid Strength · Slide 5 / 208 Slide 6 / 208 Properties of Acids Properties of Bases What is an Acid? Bases release hydroxide ions into a water solution. Acids release hydrogen ions into solutions Bases neutralize acids in a neutralization reaction. Acids neutralize bases in a neutralization reaction. Bases denature protein. Acids corrode active metals. Bases turn red litmus to blue. Bases taste bitter. Acids turn blue litmus to red. Acids taste sour.
Slide 7 / 208 Slide 8 / 208 Arrhenius Acids and Bases Brønsted-Lowry Acids and Bases Arrhenius's definition of acids and bases dates back to the 1800's. The Brønsted-Lowry definition dates back to the early 1900's It is now considered obsolete since it only relates to reactions in and is considered the modern definition of acids and bases. water - aqueous solutions. This definition is more general and it works for all reactions; Arrhenius defined acids and bases this way: not just in those in water An acid is a substance that, when dissolved in water, An acid is a proton, H + , donor. increases the concentration of hydrogen ions . HCl + H 2 O H 3 O + + Cl - A base is a proton, H + , acceptor. H 3 O + is called a hydrated proton or a hydronium ion. NH 3 + HCl NH 4+ + Cl - A base is a substance that, when dissolved in water, increases the concentration of hydroxide ions . NH 3 + H 2 O NH 4+ + OH - Slide 9 / 208 Slide 10 / 208 Brønsted-Lowry Acids and Bases Brønsted-Lowry Acids and Bases HCl +H 2 O Cl - + H 3 O + A Brønsted-Lowry acid: must have a removable (acidic) proton HCl donates the proton and acts as a Brønsted-Lowry acid. or must transfer a proton to another substance H 2 O accepts the proton and acts as a Brønsted-Lowry base. NH 3 + HCl NH 4+ + Cl - A Brønsted-Lowry base: must have a pair of nonbonding electrons or must accept a proton H N H + HCl NH 4+ + Cl - H Slide 11 / 208 Slide 12 / 208 Lewis Acids Lewis Acids Brønsted-Lowry acids replaced Arrhenius acids because the former Lewis acids are defined as electron-pair acceptors. were more general: Arrhenius acids could only be defined in aqueous (water) solutions. Brønsted-Lowry acids don't have that limitation. Atoms with an empty valence orbital can be Lewis acids. Arrehenius acids - only substances dissolved in H 2 O CH 3 CH 3 H Similarly, Brønsted-Lowry acids are limited to substances C + OH 2 H 3 C O H 3 C C + that gain or lose hydrogen. H CH 3 CH 3 Brønsted-Lowry acids - only substances that gain or lose H + Lewis Acid The most general approach is that of Lewis acids; which do not require an aqueous environment or an exchange of hydrogen.
Slide 13 / 208 Slide 14 / 208 1 A Brønsted-Lowry base is defined as a substance Lewis Bases that __________. Lewis bases are defined as electron-pair donors. Anything that could be a Brønsted-Lowry base is a Lewis base. A increases [H+] when placed in H 2 O Lewis bases can interact with things other than protons, B decreases [H+] when placed in H 2 O however. Therefore, this definition is the broadest of the three. C increases [OH-] when placed in H 2 O CH 3 CH 3 H acts aa s proton acceptor D C + OH 2 H 3 C O H 3 C C + E acts as a proton donor H CH 3 CH 3 Lewis Base Slide 14 (Answer) / 208 Slide 15 / 208 1 2 A Brønsted-Lowry base is defined as a substance A Brønsted-Lowry acid is defined as a substance that __________. that __________. A increases K a when placed in H 2 O A increases [H+] when placed in H 2 O B decreases [H + ] when placed in H 2 O B decreases [H+] when placed in H 2 O Answer D C increases [OH - ] when placed in H 2 O The Bronsted-Lowry definition C increases [OH-] when placed in H of a base is a substance that 2 O D acts as a proton acceptor is a proton acceptor. D acts aa s proton acceptor E acts as a proton donor [This object is a pull E acts as a proton donor tab] Slide 15 (Answer) / 208 Slide 16 / 208 3 Which of the following compounds could never act 2 A Brønsted-Lowry acid is defined as a substance as an acid? that __________. A SO 42- Answer A increases K a when placed in H 2 O E - HSO 4 B The Bronsted-Lowry definition of an acid is a substance that B decreases [H + ] when placed in H 2 O is a proton donor. C H 2 SO 4 [This object is a pull C increases [OH - ] when placed in H 2 O tab] NH 3 D D acts as a proton acceptor CH 3 COOH E E acts as a proton donor
Slide 16 (Answer) / 208 Slide 17 / 208 3 Which of the following compounds could never act 4 According to the following reaction model, as an acid? reactant is acting like an acid? H 2 O + H 2 SO 4 → H 3 O + + HSO 4- SO 42- A - B HSO 4 A Answer H 2 SO 4 A In order to be an acid you must be either be a substance that C H 2 SO 4 increases the H + concentration or B H 2 O a substance that donates a NH 3 D proton or an electron pair H 3 O + C acceptor. SO 42- fits none of these definitions. CH 3 COOH E - HSO 4 [This object is a pull D tab] None of the above E Slide 17 (Answer) / 208 Slide 18 / 208 4 According to the following reaction model, 5 According to the following reaction, which reactant reactant is acting like an acid? is acting like a base? H 2 O + H 2 SO 4 → H 3 O + + HSO 4- H 3 O + + HSO 4- → H 2 O + H 2 SO 4 Answer H 2 SO 4 A A H 2 SO 4 A H 2 SO 4 is donating a proton so it is the reactant that is acting like H 2 O B H 2 O B an acid. H 3 O + C H 3 O + C - [This object is a pull D HSO 4 tab] - HSO 4 D None of the above E None of the above E Slide 18 (Answer) / 208 Slide 19 / 208 5 6 For the following reaction, identify whether the According to the following reaction, which reactant compound in bold is behaving as an acid or a is acting like a base? base. H 3 O + + HSO 4- → H 2 O + H 2 SO 4 H 3 PO 4 + H 2 O → H 2 PO 4- + H 3 O + A H 2 SO 4 Answer A Acid D H 2 O B HSO 4- is accepting a proton so it Base B is the reactant that is acting like an base. H 3 O + C Neither C Both D - HSO 4 D [This object is a pull E None of the above tab] None of the above E
Slide 19 (Answer) / 208 Slide 20 / 208 6 For the following reaction, identify whether the 7 For the following reaction, identify whether the compound in bold is behaving as an acid or a compound in bold is behaving as an acid or a base. base. H 3 PO 4 + H 2 O → H 2 PO 4 - + H 3 O + Answer H 3 PO 4 + H 2 O → H 2 PO 4- + H 3 O + A H 3 PO 4 is donating a proton so it is acting like an acid. A Acid A Acid Base B Base B [This object is a pull C Both C Neither tab] D Neither Both D None of the above None of the above E E Slide 20 (Answer) / 208 Slide 21 / 208 8 Which of the following cannot act as a Lewis base? 7 For the following reaction, identify whether the compound in bold is behaving as an acid or a base. Cl - A H 3 PO 4 + H 2 O → H 2 PO 4 - + H 3 O + NH 3 B BF 3 C A Acid Answer B CN - H 2 PO 4- is accepting a proton so it Base D B is acting like an base. Both C H 2 O E Neither D [This object is a pull E None of the above tab] Slide 21 (Answer) / 208 Slide 22 / 208 8 Which of the following cannot act as a Lewis base? 9 In the reaction BF 3 + F - BF 4- BF 3 acts as a/an ____________ acid. Cl - A NH 3 B C Answer A Lewis Base is an electron pair Arrhenius A donor and any substance that is a C BF 3 Bronsted Lowry base would be a Bronsted-Lowry B Lewis base. BF 3 is not a Bronsted CN - D Lowry base and can not act as an electron pair donor. C Lewis H 2 O E [This object is a pull D Arrhenius, Bronsted-Lowry, and Lewis tab] Arrhenius and Bronsted-Lowry E
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