Slide 1 / 174 Slide 2 / 174 Properties of Acids · Acids release hydrogen ion(s) into (aqueous) solution · Acids neutralize bases in a neutralization reaction. Acids and Bases · Acids corrode active metals. · Acids turn blue litmus to red. PSI Chemistry covers the material approximately up to slide 75. · Acids taste sour. Slide 3 / 174 Slide 4 / 174 Properties of Bases Arrhenius Acids and Bases A definition of acids and bases from the 1800's · Bases release a hydroxide ion(s) into a water solution. Considered obsolete now since it only relates to reactions in · Bases neutralize acids in a neutralization reaction. water, aqueous solutions. · Bases denature protein. He defined acids and bases this way: · An acid is a substance that, when dissolved in water, · Bases turn red litmus to blue. increases the concentration of hydrogen ions. · Bases taste bitter. · A base is a substance that, when dissolved in water, increases the concentration of hydroxide ions. Slide 5 / 174 Slide 6 / 174 Brønsted-Lowry Acids and Bases Brønsted-Lowry Acids and Bases A Brønsted-Lowry acid: must have a removable (acidic) proton A more modern definition: formulated in the early 1900's or must transfer a proton to another substance More general since it works for all reactions; not just in water · An acid is a proton, H + , donor. A Brønsted-Lowry base: must have a pair of nonbonding electrons · A base is a proton, H + , acceptor. or must accept a proton
Slide 7 / 174 Slide 8 / 174 1 A Bronsted-Lowry base is 2 A Bronsted-Lowry acid is defined as a substance defined as a substance that __________. that __________. A increases [H+] when placed in H 2 O A increases K a when placed in H 2 O B decreases [H+] when placed in H 2 O decreases [H + ] when placed in H 2 O B C increases [OH-] when placed in H 2 O increases [OH - ] when placed in H 2 O C D acts as a proton acceptor E acts as a proton donor D acts as a proton acceptor E acts as a proton donor Slide 9 / 174 Slide 10 / 174 Brønsted-Lowry Acids and Bases Lewis Acids HCl + H 2 O # Cl - + H 3 O + · Brønsted-Lowry acids replaced Arrhenius acids because the former were more general: Arrhenius acids could only be HCl donates the proton and defined in aqueous (water) solutions. Brønsted-Lowry acids acts as a Brønsted-Lowry don't have that limitation. + acid · Similarly, Brønsted-Lowry acids are limited to substances H 2 O accepts the proton and that gain or lose hydrogen. But there are acids and bases acts as a Brønsted-Lowry that don't. _ base + · The most general approach is that of Lewis acids; which H 3 O + is called a hydrated don't require an aqueous environment or an exchange of hydrogen. proton or a hydronium ion. It is also written as H + Slide 11 / 174 Slide 12 / 174 Lewis Bases Lewis Acids · Lewis bases are defined as electron-pair donors. · Anything that could be a Brønsted-Lowry base is a Lewis · Lewis acids are defined as electron-pair acceptors. base. · Atoms with an empty valence orbital can be Lewis acids. · Lewis bases can interact with things other than protons, however. Therefore, this definition is the broadest of the three.
Slide 13 / 174 Slide 14 / 174 3 Which of the following compounds could never act 4 According to the following reaction model, which as an acid? reactant is acting like an acid? H 2 O + H 2 SO 4 → H 3 O + + HSO 4 - 2- SO 4 A - B HSO 4 H 2 SO 4 A C H 2 SO 4 B H 2 O D NH 3 H 3 O + C CH 3 COOH E - HSO 4 D None of the above E Slide 15 / 174 Slide 16 / 174 5 According to the following 6 For the following reaction, reaction, which reactant is identify whether the acting as a base? compound in bold is behaving as an acid or a H 3 O + + HSO 4 - → H 2 O + H 2 SO 4 base. - + H 3 O + H 3 PO 4 + H 2 O → H 2 PO 4 H 2 SO 4 A Acid A H 2 O B Base B H 3 O + C Neither C - HSO 4 D D Both None of the above E None of the above E Slide 17 / 174 Slide 18 / 174 7 For the following reaction, 8 For the following reaction, identify whether the identify whether the compound in bold is compound in bold is behaving as an acid or a behaving as an acid or a base. base. - + H 3 O + - + H 3 O + H 3 PO 4 + H 2 O → H 2 PO 4 H 3 PO 4 + H 2 O → H 2 PO 4 Acid A Acid A Base B Base B Both Both C C Neither D Neither D None of the above None of the above E E
Slide 19 / 174 Slide 20 / 174 Conjugate Acids and Bases Acids in Water What Happens When an Acid Dissolves in Water? · The term conjugate comes from the Latin word “conjugare,” meaning “to join together.” + Which is the acid? · Reactions between acids and bases always yield Which is the base? their conjugate bases and acids. · Water acts as a Brønsted-Lowry _ + base and takes a proton (H+) remove H + from the acid. · As a result, the conjugate base HNO 2 (aq) + H 2 O(l) NO 2 - (aq) + H 3 O - (aq) of the acid and a hydronium ion conjugate Conjugate Acid Base are formed. base acid add H+ Slide 21 / 174 Slide 22 / 174 Conjugate Acids and Bases Amphoteric Substances remove H + If a substance can act both as an acid and base, it is known as amphoteric. For example, water can act as a base or acid depending on HNO 2 (aq) + H 2 O(l) NO 2 - (aq) + H 3 O - (aq) the situation. conjugate Conjugate Acid Base base acid ↔ Cl - + H 3 O + HCl + H 2 O add H+ Above, water accepts a proton, thus acting as After the acid donates a proton, the result is called its a base. conjugate base. ↔ NH 4 + + OH - NH 3 +H 2 O After the base accepts a proton, the result is called its Above, water donates a proton, thus acting as conjugate acid. an acid. Slide 23 / 174 Slide 24 / 174 Amphoteric Substances 9 A substance that is capable of acting as both an acid and as a base is __________. Another term for amphoteric is amphiprotic. For each of the following substances, write two equations, one A autosomal showing it as a Bronsted-Lowry acid and another showing it as a Bronsted-Lowry base. B conjugated C amphoteric - HCO 3 D saturated E miscible - HSO 4 H 2 O
Slide 25 / 174 Slide 26 / 174 What is the conjugate acid of NH 3 ? 10 11 + , What are the conjugate bases of HClO 4 , H 2 S, PH 4 - ? HCO 3 A NH 3 + NH 2 A + , HS-, PH 3 - , CO 3 - ClO 4 B + NH 3 C - , HS - , PH 3 , CO 3 2- ClO 4 + NH 4 B D NH 4 OH 2- , HS 2- , PH 3 3- , CO 3 2- E ClO 4 C Slide 27 / 174 Slide 28 / 174 Acid and Base Strength Acid and Base Strength Acid Base Acid Base · Strong acids are 100% HCl Cl - 100% HCl Cl - ionized - completely dissociated in H 2 SO 4 HSO 4 ionized - H 2 SO 4 HSO 4 in H 2 O Base strength increases - HNO 3 NO 3 in H 2 O Base strength increases HNO 3 NO 3 - water. + H 2 O H 3 O H 3 O + H 2 O - SO 4 2- HSO 4 · Weak acids only - SO 4 2- HSO 4 H 3 PO 4 H 2 PO 4 - - H 3 PO 4 H 2 PO 4 HF F- dissociate partially in water. HF F- · Their conjugate bases are HC 2 H 3 O 2 C 2 H 3 O 2 - - HC 2 H 3 O 2 C 2 H 3 O 2 - Acid strength increases H 2 CO 3 HCO 3 - Acid strength increases H 2 CO 3 HCO 3 Negligible Weak g n o r t S quite weak. H 2 S HS - Negligible Weak g n o r t S Negligible k a e W Strong - Negligible k a e W H 2 S HS Strong - HPO 4 2- H 2 PO 4 · Their conjugate bases are - HPO 4 2- H 2 PO 4 NH 4 + NH 3 + NH 3 NH 4 - CO 3 2- HCO 3 weak bases. - CO 3 2- HCO 3 HPO 4 2- PO 4 3- 2- PO 4 3- HPO 4 - H 2 O OH H 2 O OH - OH - O 2- 100% OH - O 2- H 2 H - 100% - protonated H 2 H - protonated CH 4 CH 3 in H 2 O CH 4 CH 3 - in H 2 O Slide 29 / 174 Slide 30 / 174 Acid and Base Strength Strong Acids Acid Base The seven strong acids are: 100% - HCl Cl ionized - H 2 SO 4 HSO 4 in H 2 O Base strength increases HNO 3 NO 3 - · HCl hydrochloric acid + H 2 O H 3 O HSO 4 - SO 4 2- · HBr hydrobromic acid - H 3 PO 4 H 2 PO 4 · Substances with negligible HF F- · HI hydroiodic acid - HC 2 H 3 O 2 C 2 H 3 O 2 acidity do not dissociate in Acid strength increases H 2 CO 3 HCO 3 - · HNO 3 nitric acid Negligible Weak g n o r t S k a e W Strong - H 2 S HS water. They will not readily H 2 PO 4 - HPO 4 2- · H 2 SO 4 sulfuric acid + NH 3 NH 4 give up protons. - CO 3 2- HCO 3 · HClO 3 chloric acid 2- PO 4 3- HPO 4 - H 2 O OH · HClO 4 perchloric acid - O 2- OH · Their conjugate bases are 100% - H 2 H protonated - CH 4 CH 3 exceedingly strong. in H 2 O Memorize this list.
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