CA0426C Mono & Polyprotic Acids. CA-0426: Mono & Polyprotic Acids 1) - You may now know that HCl and...
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Transcript of CA0426C Mono & Polyprotic Acids. CA-0426: Mono & Polyprotic Acids 1) - You may now know that HCl and...
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 (HClO4);Nitric acid (HNO3);(Hydrobromic) acid (HBr) and;Acetic acid (which is a/k/a ethanoic acid) (CH3COOH)
CA-0426: Mono & Polyprotic AcidsOther monoprotic acids are:Perchloric acid (HClO4);Nitric acid (HNO3);(Hydrobromic) acid (HBr) and;Acetic acid (which is a/k/a ethanoic acid) (CH3COOH)
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 AcidsAcetic acid (which is a/k/a ethanoic acid) (CH3COOH)
5) - Looking at the ethanoic acid molecule CH3COOH (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 AcidsAcetic acid (which is a/k/a ethanoic acid) (CH3COOH)
6) - Only one of the four hydrogen atoms in the CH3COOH 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 AcidsAcetic acid (which is a/k/a ethanoic acid) (CH3COOH)
8) - In CH3COOH (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 H2SO4
Carbonic acid (H2CO3)
S OOH H
O
O
C
O
OO
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 H2SO4
Carbonic acid (H2CO3)
S OOH H
O
O
C
O
OO
H
H
CA-0426: Mono & Polyprotic Acids
10) - Acids that contain two ionizable hydrogen atoms per (molecule) are called (di)protic acids.
(Sulfuric) acid H2SO4
Carbonic acid (H2CO3)
S OOH H
O
O
C
O
OO
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 (H3PO4)(Boric) acid H3BO3
P OOH H
O
O
B
O
OO
HH
H H
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 (H3PO4)(Carbonic) acid H2CO3
P OOH H
O
O
C
O
OO
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
P OOH H
O
O
OHH
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
P OOH H
O
O
OHH
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
P OOH
O
O
OHH
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
P OOH
O
O
OHH
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.
CO2 (g) + H2O (l) H2CO3 (aq)
C
O
O
O
HH
C
O
O
O
HH
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) + H2O (l) Ca+2 (aq) + 2OH— (aq)
Ca
O
O
HH
CA-0426: Mono & Polyprotic Acids - Anhydrides
Similarly, SO3 is the (anhydride) of H2SO4 [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)H2Se
STEP 1: H2Se(aq) + H20(l) H3O+ (aq) + HSe— (aq)
Step 2: HSe— (aq) + H20(l) H3O+ (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)H3AsO4
Step 1: H3AsO4 (aq) + H20(l) H3O+ (aq) + H2AsO4 -- (aq)
Step 2: H2AsO4 -- (aq) + H20(l) H3O+ (aq) + HAsO4
--2 (aq)
Step 3: HAsO4
--2 (aq) + H20(l) H3O+ (aq) + AsO4 --3 (aq)
CA-0426: Mono & Polyprotic Acids - Anhydrides
Pg. 601 prob. 3 – list the steps of ionization of the mono/polyprotic acids:
C) H2SO3
Step 1: H2SO3 (aq) + H20(l) H3O+ (aq) + HSO3 -- (aq)
Step 2: HSO3 -- (aq) + H20(l) H3O+ (aq) + SO3
--2 (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:
C C C
O
O
O
OH
HH
H