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Basic Chemistry IV

Basic Chemistry IV. Vladimíra Kvasnicová. Water, solutions, and solubility. amphiprotic properties of water : H 2 O + H 2 O  H 3 O + + OH - aqueous solutions (aq) HCl, NaOH, H 2 CO 3 , NH 3 K = [H 3 O + ] x [OH - ] [H 2 O] 2

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Basic Chemistry IV

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  1. Basic Chemistry IV Vladimíra Kvasnicová

  2. Water, solutions, and solubility • amphiprotic properties of water: H2O + H2O H3O+ + OH- • aqueous solutions (aq) HCl, NaOH, H2CO3, NH3 K = [H3O+] x [OH-] [H2O]2 • the equilibrium constant is CONSTANT:if concentration of H3O+ increasesthe concentration of OH- decreasesand vice versa

  3. Dissociation of water: H2O ↔ H+ + OH- H2O+H+ + OH-↔H3O++ OH- H2O + H2O ↔ H3O+ + OH- Kdis = [H3O+] x [OH-] [H2O]2 Kdis x [H2O]2 = [H3O+] x [OH-] Kdis x [H2O]2 = constant, because [H2O] is manifold higher than [H3O+] or [OH-] Kw = constant = ionic product of water Kw = [H3O+] x [OH-]

  4. Kw = [H3O+] x [OH-] = 10-14 pKW = pH + pOH = 14 pK = - log K pH = - log [H3O+]pOH = - log [OH-] 10-14= [H3O+] x [OH-] / log log10-14= log ([H3O+] x [OH-] ) log 10-14= log [H3O+] + log [OH-] -14= log [H3O+] + log [OH-] / x (-1) 14= - log [H3O+] - log [OH-] ↓ ↓ ↓ pKW =pH+ pOH 14 = 7 + 7 in pure water

  5. Water, solutions, and solubility H2O + H2O H3O+ + OH- • ionic product of water Kw = [H3O+] x [OH-] = 10-14 pKw = pH + pOH = 14 • pH = -log [H3O+]

  6. pH= negative logarithm of activity ofoxonium cations acidic neutral basic pH scale is a logarithmic scale for expressing the acidity or alkalinity of a solution http://www2.bc.cc.ca.us/bio16/images/02-14_ph_scale_1.jpg

  7. pH = - log a(H3O+) a = γ x c a = activity γ = activity coefficient c = concentration (mol /L) in diluted (mM) solutions: γ = 1  a = c pH = - log c(H3O+) c(H3O+) = [H3O+] = molar concentration simplification:c(H3O+)= cH+

  8. pKW = pH + pOH = 14 => water: [H3O+] = 10–7 (pH = 7) [OH-] = 10–7 (pOH = 7) simplification: [H3O+] = [H+] = c(H+) => pH = – log c(H+) pH = 0 – 14 pH 0 -------------- 7 --------------14 acidic neutral basic If [H+] decreases, [OH-] increasesKW is 10-14 If [OH-] decreases, [H+] increases(= constant !)

  9. strong acids (HA) [HA] = [H+] HA → H+ + A- pH = - log c(H+) = - log cHA strong bases (BOH)[BOH] = [OH-] BOH → B+ + OH- pOH = - log cBOH pH = 14 - pOH

  10. weak acids (HA)[HA] ≠ [H+] Kdis ≤ 10–2 HA ↔ H+ + A- Kdis = [H+] [A-][H+] = [A-] [HA] = cHAKdis = Ka[HA] Ka= [H+]2cHA pH = ½ pKa - ½ log cHA - log Ka = pKa

  11. weak acids (HA)[HA] ≠ [H+] Kdis ≤ 10–2 HA ↔ H+ + A- Kdis = [H+] [A-][H+] = [A-] [HA] = cHAKdis = Ka[HA] Ka= [H+]2cHA KaxcHA = [H+]2/log log (KaxcHA ) = 2 x log [H+] log Ka + log cHA = 2 x log [H+] / ½ ½ log Ka + ½ log cHA = log [H+] / x (-1) -½ log Ka - ½ log cHA = - log [H+] - log Ka = pKa ½ pKa - ½ log cHA = pH =>pH = ½ pKa - ½ log cHA

  12. weak acids (HA)[HA] ≠ [H+] Kdis ≤ 10–2 HA ↔ H+ + A- pH = ½ pKa - ½ log cHA weak bases (BOH)[BOH] ≠ [OH-]Kdis = [B+] [OH-] BOH ↔ B+ + OH-[BOH] pOH = ½ pKb - ½ log cBOH => pH of basic solutions: pH + pOH = 14 pH = 14 - pOH

  13. Important equations pH = - log c(H+)pK = - log K pH + pOH = 14 ACIDS: pH = - log cHA pH = ½ pKa - ½ log cHA BASES: pOH = - log cBOH pOH = ½ pKb - ½ log cBOH pH = 14 – pOH

  14. 0.1 M HCl 0.001 M HCl 0.05 M H2SO4 0.1 M NaOH 0.001 M NaOH 0.05 M Ba(OH)2 pH = 1 pH = 3 pH = 1 pOH = 1 → pH = 13 pOH = 3 → pH = 11 pOH = 1 → pH = 13 Exercisescalculate the pH of Dilution 100x  pH is changed by 2 units!

  15. 0.1 M acetic acid, pKa = 4.76 0.001 M acetic acid 0.001 M H2CO3, pKa1 = 6,35 pKa2 = 10.25 0.1 M NH3, pKb = 4.74 0.001 M NH3 pH = 2.88 pH = 3.88 pH = 4.68 pOH = 2.87→ pH = 11.13 pOH = 3.87→ pH = 10.13 Exercisescalculate the pH of Dilution 100x  pH is changed by 1 unit!

  16. Organic compounds • „compounds of carbon“ • hydrocarbon skeleton: C, H • saturated: CH3-(CH2)n-CH3 • unsaturated: -CH=CH- or –C=C- • heteroatoms:O, N, S, halogens • heterocyclic compounds • hydrocarbon derivatives(in functional groups) • aliphatic or aromatic compounds

  17. Shape of molecules σ-bond C-C π-bond C=C C≡C Alkanes • hybridization sp3 – tetrahedralshape (4  bonds) ethane

  18. Alkenes • hybridization sp2 – trigon (3  and 1 ) Alkynes • hybridization sp – linear (2  and 2 ) ethene ethyne

  19. Aromatic compounds • delocalization of π-elektrons • more resonance structures • planar molecules • Hűckel rule: 4n + 2 = number of -electronsn = 1, 2, 3,...

  20. Chemical properties • hydrocarbons are hydrophobic (= lipophilic) because are nonpolar • hydrocarbon derivatives:polar functional group + nonpolar tail • reactivity: • multiple bonds • functional groups • complete oxidation (= burning) of a hydrocarbon skeleton → CO2 + H2O

  21. Important chemical reactions of organic compounds • substitution(= replacement)CH4 + Cl2→ CH3Cl + HCl • addition(multiplicity of chemical bond is lowered)CH2=CH2 + H2O→ CH3-CH2-OH • elimination(new multiple bond is often formed,small molecule is released)CH3-CH2-OH→ CH2=CH2 + H2O • rearrangement(= formation of an isomer)CH2=C(OH)-COOH → CH3-C(O)-COOH

  22. Isomerism isomers = compounds having the same molecular formula but different molecular structures (costitution) ordifferent arrangements of atoms in space (configuration) a) constitutional (structural) isomers • different type of a hydrocarbon chain • different position of a substituent or a multiple bond • different functional groups • keto-enol isomers (= tautomers) b)configurational isomers (stereoisomers) • optical isomers (= enantiomers) are „mirror images“ • cis-trans isomers (= geometrical isomers)

  23. Hydrocarbon derivatives carboxylic acid R-COOH • aliphatic / -oic acid (-dioic acid) / - tricarboxylic acid • cyclic / - carboxylic acid • hydrocarbon–oic acid (propanoic acid) • common names (propionic acid) reactions: dissociation→ carboxylate (= anion) reduction→ aldehyde

  24. Hydrocarbon derivatives sulfonic acid R-SO3H • sulfo-/ sulfonic acid • hydrocarbonsulfonic acid (methane sulfonic acid) reactions: dissociation→ sulfonate (= anion) reduction→ thiol

  25. Hydrocarbon derivatives aldehyde R-CHO • aliphatic formyl- / -al • cyclic - carbaldehyde • hydrocarbon–al (methanal) • common names (formaldehyde) reactions: oxidation→ carboxylic acid reduction→ primary alcohol

  26. Hydrocarbon derivatives ketone R1-CO-R2 • aliphatic oxo- or keto- / -one • cyclic unsaturated diketones = quinones • hydrocarbon–one (propanone) • hydrocarbon rests ketone (dimethyl ketone) • common names (acetone) reactions: reduction→ secondary alcohol

  27. Hydrocarbon derivatives alcohol R-OH • aliphatic hydroxy- / -ol (-diol, -triol) • aromatic = phenols common names • sulfur-containing = thiolssulfanyl- / -thiol • hydrocarbon–ol (methanol) • hydrocarbon restalcohol (methyl alcohol) reactions: oxidation→ aldehyde or ketone dehydration→ unsaturated hydrocarbon

  28. Hydrocarbon derivatives amine R-NH2 R1-NH-R2 R1-N(R2)-R3 • amino- / -amine (-diamine) • hydrocarbon rest(s)–amine (propylamine) • hydrocarbon-amine (propaneamine) reactions: oxidation→ nitro compound protonation→ ammonium cation

  29. Hydrocarbon derivatives ether R1-O-R2 • alk(yl)oxy- / -ether • sulfur-containing = sulfide / - sulfide R1-S-R2 • hydrocarbon restsether (ethyl propyl ether)

  30. Hydrocarbon derivatives halogen derivative R-X X = F, Cl, Br, I halogeno-/ (fluoro-, chloro-, bromo-, iodo-) • halogeno- hydrocarbon (chloromethane) nitro derivative R-NO2 nitro- / • nitro- hydrocarbon (nitromethane)

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