CA0426C Mono & Polyprotic Acids

CA-0426: Mono & Polyprotic Acids 1) - You may now know that HCl and HF are (acids) because they can (donate) a (hydrogen ion) = a “proton”; in an acid- base reaction. p⁺ Hydrogen atom 9p⁺ Fluorine atom H₂O - Added Ion (H⁺) “Proton” 9n° Fluorine anion F⁻

CA-0426: Mono & Polyprotic Acids 2) - From their chemical formulas (HCl and HF) you can see that EACH “acid” can donate only (one) hydrogen ion. This is called a (monoprotic) acid [where “mono” means “one” and “protic” means “proton”.] p⁺ Hydrogen atom 9p⁺ Fluorine atom H₂O - Added Ion (H⁺) “Proton” 9n° Fluorine anion F⁻

CA-0426: Mono & Polyprotic Acids 3) - Other monoprotic acids are: Perchloric acid (HClO 4 ); Nitric acid(HNO 3 ); (Hydrobromic) acid(HBr) and; Acetic acid (which is a/k/a ethanoic acid)(CH 3 COOH)

CA-0426: Mono & Polyprotic Acids Other monoprotic acids are: Perchloric acid (HClO 4 ); Nitric acid(HNO 3 ); (Hydrobromic) acid(HBr) and; Acetic acid (which is a/k/a ethanoic acid)(CH 3 COOH) 4) - Given the four listed monoprotic acids above in statement (3) – go back and highlight in red color the hydrogen atom in each that will be donated in an “acid-base” pair reaction.

CA-0426: Mono & Polyprotic Acids Acetic acid (which is a/k/a ethanoic acid)(CH 3 COOH) 5) - Looking at the ethanoic acid molecule CH 3 COOH (also known as acetic acid) you can see it contains (four) hydrogen atoms. Can ethanoic acid donate (more than) one hydrogen ion? (NO); it contains only one (ionizable) hydrogen atom.

CA-0426: Mono & Polyprotic Acids Acetic acid (which is a/k/a ethanoic acid)(CH 3 COOH) 6) - Only one of the four hydrogen atoms in the CH 3 COOH molecule can be (donated) because only those hydrogen atoms bonded to (electronegative) elements by (polar) bonds are ionizable [and therefore; can be donated as an acid does.] Electronegativity – The bigger the difference… … the bigger the ability to “hang onto” electron(s) & strong tendency to “dissociate” (break apart) in water. Oxygen (O) > Hydrogen (H) Carbon (C) ≈ Hydrogen (H)

CA-0426: Mono & Polyprotic Acids H-F 7) - In an HF (hydrofluoric acid) molecule, the hydrogen atom is bonded to a fluorine atom, which has the (highest) electronegativity of all the elements. Electronegativity – The bigger the difference… … the bigger the ability to “hang onto” electron(s) & strong tendency to “dissociate” (break apart) in water. Fluorine (F) >> Hydrogen (H)

CA-0426: Mono & Polyprotic Acids Acetic acid (which is a/k/a ethanoic acid)(CH 3 COOH) 8) - In CH 3 COOH (ethanoic acid) – three of the four hydrogens are bonded to a carbon atom which have almost the same (electronegativity) as hydrogen meaning they are nearly equal. Only the hydrogen atom bonded to the electronegative (oxygen) atom can be donated. Electronegativity – The bigger the difference… … the bigger the ability to “hang onto” electron(s) & strong tendency to “dissociate” (break apart) in water. Oxygen (O) > Hydrogen (H) Carbon (C) ≈ Hydrogen (H)

CA-0426: Mono & Polyprotic Acids 9) - Some acids do donate (more than) one hydrogen ion. For example: (Sulfuric) acid H 2 SO 4 Carbonic acid(H 2 CO 3 ) SOOHH O O C O O O H H

CA-0426: Mono & Polyprotic Acids 9) - Can each donate (two) hydrogen ions. In each… both [of the] hydrogen atoms are attached to (oxygen) atoms [which are higher electronegativity than hydrogen]. (Sulfuric) acid H 2 SO 4 Carbonic acid(H 2 CO 3 ) SOOHH O O C O O O H H

CA-0426: Mono & Polyprotic Acids 10) - Acids that contain two ionizable hydrogen atoms per (molecule) are called (di)protic acids. (Sulfuric) acid H 2 SO 4 Carbonic acid(H 2 CO 3 ) SOOHH O O C O O O H H

CA-0426: Mono & Polyprotic Acids 11) - In a similar way, acids that contain (three) ionizable hydrogen atoms per molecule allowing them to donate three hydrogen (ions) or protons are called (tri)protic acids. Phosphoric acid(H 3 PO 4 ) (Boric) acid H 3 BO 3 POOHH O O B O O O H H HH

CA-0426: Mono & Polyprotic Acids 12) - The term polyprotic acid can be used for any acid that has more than (one) ionizable hydrogen (atom). Phosphoric acid(H 3 PO 4 ) (Carbonic) acid H 2 CO 3 POOHH O O C O O O H H H

CA-0426: Mono & Polyprotic Acids 13) - All polyprotic acids ionize in (steps) … [the number of “steps” = to the number of ionizable hydrogen atoms]. Eg. Phosphoric acid-Dissociated & Ionized in water POOHH O O O H H H

CA-0426: Mono & Polyprotic Acids 13) - All polyprotic acids ionize in (steps) … [the number of “steps” = to the number of ionizable hydrogen atoms]. STEP 1 POOHH O O O H H H

CA-0426: Mono & Polyprotic Acids 13) - All polyprotic acids ionize in (steps) … [the number of “steps” = to the number of ionizable hydrogen atoms]. STEP 2 POOH O O O H H H

CA-0426: Mono & Polyprotic Acids 13) - All polyprotic acids ionize in (steps) … [the number of “steps” = to the number of ionizable hydrogen atoms]. STEP 3 POOH O O O H H

CA-0426: Mono & Polyprotic Acids - Anhydrides 14) - Some (oxides) can become acids or bases by adding the elements contained in water. These compounds are called (anhydrides). Oxides of (non-metallic) elements such as (carbon), (sulfur), or (nitrogen), produce an (acid) in aqueous solution. C O O O HH

CA-0426: Mono & Polyprotic Acids - Anhydrides 14) - Oxides of (metallic) elements usually form (basic) solutions. Ca O O HH

CA-0426: Mono & Polyprotic Acids - Anhydrides Eg. carbon di(oxide), an oxide of the non-metal carbon – forms an aqueous solution of (carbonic) acid. CO 2 (g) + H 2 O (l)  H 2 CO 3 (aq) C O O O HH C O O O H H

CA-0426: Mono & Polyprotic Acids - Anhydrides 14) - Eg. calcium (oxide), an oxide of the metal calcium – forms an aqueous solution of calcium (hydroxide). CaO (s) + H 2 O (l)  Ca +2 (aq) + 2OH — (aq) Ca O O HH

CA-0426: Mono & Polyprotic Acids - Anhydrides Similarly, SO 3 is the (anhydride) of H 2 SO 4 [sulfuric acid] Similarly, MgO is the (anhydride) of Mg(OH) 2 [magnesium hydroxide] S O O O Mg O NON-metal Metal base

CA-0426: Mono & Polyprotic Acids - Anhydrides Pg. 601 prob. 3 – list the steps of ionization of the mono/polyprotic acids: a)H 2 Se STEP 1: H 2 Se (aq) + H 2 0 (l)  H 3 O + (aq) + HSe — (aq) Step 2: HSe — (aq) + H 2 0 (l)  H 3 O + (aq) + Se —2 (aq)

CA-0426: Mono & Polyprotic Acids - Anhydrides Pg. 601 prob. 3 – list the steps of ionization of the mono/polyprotic acids: b)H 3 AsO 4 Step 1: H 3 AsO 4 (aq) + H 2 0 (l)  H 3 O + (aq) + H 2 AsO 4 -- (aq) Step 2: H 2 AsO 4 -- (aq) + H 2 0 (l)  H 3 O + (aq) + HAsO (aq) Step 3: HAsO (aq) + H 2 0 (l)  H 3 O + (aq) + AsO (aq)

CA-0426: Mono & Polyprotic Acids - Anhydrides Pg. 601 prob. 3 – list the steps of ionization of the mono/polyprotic acids: C) H 2 SO 3 Step 1: H 2 SO 3 (aq) + H 2 0 (l)  H 3 O + (aq) + HSO 3 -- (aq) Step 2: HSO 3 -- (aq) + H 2 0 (l)  H 3 O + (aq) + SO (aq)

CA-0426: Mono & Polyprotic Acids - Anhydrides Pg. 601 prob. 9 – In the structural formula below… identify any hydrogen atoms that are likely to be ionizable: CCC O O O O H H H H