Part 18 Equilibria Involving Acids bases

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Part 18 Equilibria Involving Acids & bases

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ARRHENIUS THEORY for ACIDS and BASES ACIDS : deliver hydrogen particles (protons), H + , in arrangement BASES : create hydroxide particles, OH - ,in arrangement, NEUTRALIZATION : H + OH -  H 2 O Problems with Arrhenius Theory * H 3 O + : Hydronium particle instead of H + * OH(H 2 O) 3 - display in arrangement, not OH - * Other substances likewise have acidic or fundamental properties

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H + encompassed by four H-reinforced H 2 O atoms H 9 O 4 +

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OH - encompassed by three H-fortified H 2 O particles OH(H 2 O) 3 -

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Bronsted-Lowery Theory of Acids and Bases Acid – any substance giving a proton, H + Base – any substance tolerating a proton Conjugate Acid-Base Pairs : e.g. HF + NH 3  NH 4 + F - corrosive 1 base 2 corrosive 2 base 1 AMPHOTERIC substances have both acidic and fundamental properties. Mono-, di-, tri-,… … . to polyprotic acids . Acidic versus nonacidic H particles in mixes.

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For each of the accompanying responses, recognize the corrosive, the base, the conjugate base, and the conjugate corrosive H 2 O + H 2 O  H 3 O + OH - H 2 PO 4 - + H 2 PO 4 -  H 3 PO 4 + HPO 4 2-H 2 SO 4 + H 2 O  H 3 O + HSO 4 - H 2 PO 4 - + H 2 O  H 3 PO 4 + OH - CO 2 + 2H 2 O  HCO 3 - + H 3 O + H 2 PO 4 - + H 2 O  HPO 4 2-+ H 3 O + Fe(H 2 O) 6 3+ + H 2 O  Fe(H 2 O) 5 (OH) 2+ + H 3 O + HCN + CO 3 2- CN - + HCO 3 -

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Graphic representations of solid and powerless corrosive equilibria Strong Acid: 100% Dissociation into particles HA (aq) + H 2 O (l)  H 3 O + (aq) + A - (aq) Equilibrium Favors undissociated corrosive Weak Acid: Very little Dissociation into particles

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Acid quality versus conjugate base quality

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Bronsted-Lowery Theory: Acid and Base Strengths Proton exchanges happen from a Strong corrosive to a solid base e.g. HCl + NaOH  H 2 O + NaCl Weak corrosive to solid base e.g. CH 3 COOH + NaOH  ?? Feeble base to a more grounded base e.g. HSO 4 1-+ HSO 3 1- ??? Will a Reaction happen between … .. a. HS 1-and F 1-?? b. HCl and ClO 2 1-?? c. HCl and ClO 4 1-?? d. HCl and HNO 3 ??

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Relative qualities of some Bronsted-Lowry acids and their conjugate bases Acid Base Strongest HClO 4 ClO 4 - Weakest Acids H 2 SO 4 HSO 4 - bases HI I - HBr Br - HCl Cl - HNO 3 NO 3 - H 3 O + H 2 O HSO 4 - SO 4 2- H 2 SO 3 HSO 3 - H 3 PO 4 H 2 PO 4 - HNO 2 NO 2 - HF F - CH 3 CO 2 H CH 3 CO 2 - H 2 CO 3 HCO 3 - H 2 S HS - NH 4 + NH 3 HCN CN - HCO 3 - CO 3 2- HS - S 2- H 2 O OH - Weakest NH 3 NH 2 - Strongest Acid OH - O 2-bases

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Bronsted-Lowery Theory: Acid and Base Strengths LEVELING EFFECT of SOLVENTS : The most grounded corrosive in a dissolvable is the conjugate corrosive of the dissolvable. The most grounded base is the conjugate base. Corrosive H 3 O + in water Base OH - in water

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H 2 O( l ) H 2 O( l ) OH - ( aq ) H 3 O + ( aq ) Autoionization of Water and the pH Scale +

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Autoionization of Water H 2 O(l) + H 2 O(l)  H 3 O + (aq) + OH - (aq) K w = [H 3 O + ] [OH - ] = 1.0 x 10 - 14 at 25 o C At balance [H 3 O + ] = [OH - ] = 1.0 x 10 - 7 K w changes with temperature but [H 3 O + ] = [OH - ]

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pH and pOH SCALES pH = - log [H 3 O + ] pOH = - log [OH - ]

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pH, pOH CALCULATIONS pH = - log [H 3 O + ] pOH = - log [OH - ] Kw = [H 3 O + ] [OH - ] = 1.0 x 10 - 14 so p[H 3 O + ] + p[OH - ] = 14.00 or pH = 14.00 – pOH CALULATE SOME pH and pOH VALUES

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(Household Cleaner) Blood [H+] pH 10-14 14 1 M NaOH 10-13 13 Basic 10-12 12 Ammoni a 10-11 11 10-10 10 10-9 9 10-8 8 Neutral 10-7 7 Pure Water 10-6 6 10-5 5 10-4 4 10-3 3 Acidic 10-2 2 10-1 1 1 0 Milk Vinegar Lemon juice Stomach corrosive 1 M HCl

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Calculate the pH of every arrangement: a. [H + ] = 1.4 x 10 - 3 M e. [OH - ] = 8 x 10 - 11 M b. [H + ] = 2.5 x 10 - 10 M f. [OH - ] = 5.0 M c,. [H + ] = 6.1 M g. pOH = 10.5 d. [OH - ] = 3.5 x 10 - 2 M h. pOH = 2.3 Calculate [H + ] and [OH - ] for every arrangement : a. pH = 7.41 (the typical pH of blood) b. pH = 15.3 c. pH = - 1.0 e. pOH = 5.0 d. pH = 3.2 f. pOH = 9.6 what number huge figures are there in the numbers: 10.78, 6.78, 0.78? On the off chance that these were pH qualities, to what number of huge figures would you be able to express the [H + ]? Clarify any inconsistencies between your responses to the two questions.

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Values of Kw as a component of temperature are as per the following: Temp ( o C) Kw 0 1.14 x 10 - 15 25 1.00 x 10 - 14 35 2.09 X 10 - 14 40 2.92 x 10 - 14 50 5.47 x 10 - 14 a. Is the autoionization of water exothermic or endothermic? b. What is the pH of unadulterated water at 50 o C?

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Values of Kw as an element of temperature are as per the following: Temp ( o C) Kw 0 1.14 x 10 - 15 25 1.00 x 10 - 14 35 2.09 X 10 - 14 40 2.92 x 10 - 14 50 5.47 x 10 - 14 a. Is the autoionization of water exothermic or endothermic? b. What is the pH of unadulterated water at 50 o C? c. Restate your responses to water at 50 o C. Which of the three criteria for lack of bias is generally broad? d. From a plot of ln(Kw) versus 1/T (utilizing the Kelvin scale), gauge Kw at 37 o C, ordinary physiological temperature. e. What is the pH of an impartial arrangement at 37 o C?

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- 28 - 29 Y = - 9.2338 – 6870.6x R^2 = 0.999 - 30 ln Kw - 31 - 32 - 33 - 34 - 35 0.0028 0.0030 0.0032 0.0034 0.0036 1/T

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pH MEASUREMENT Indicators : shaded feeble acids and bases pH Meters : Glass layer with a voltage (potential) difference over the glass. pH and BODY CHEMISTRY Normal pH 7.3 to 7.5 Acidosis pH < 7.3 Alkalosis pH > 7.45 Body Chemistry is " cushioned " with bicarbonates (HCO 3 - ) dihydrogenphosphates (H 2 PO 4 - ) and proteins which keep up a consistent pH

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WEAK ACIDS IONIZATION CONSTANTS HA (aq) + H 2 O (l)  H 3 O + (aq) + A - (aq) K a qualities at 25 o C are known and arranged for an extensive number of feeble acids.

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Graphic representations of solid and powerless corrosive equilibria Strong Acid: 100% Dissociation into particles HA (aq) + H 2 O (l)  H 3 O + (aq) + A - (aq) Equilibrium Favors undissociated corrosive Weak Acid: Very little Dissociation into particles

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Values of Ka for Some Common Monoprotic Acids Formula Name Value of K a * HSO 4 - Hydrogen sulfate ion 1.2 x 10 - 2 HClO 2 Chlorous acid 1.2 x 10 - 2 HC 2 H 2 ClO 2 Monochloroacetic acid 1.35 x 10 - 3 HF Hydrofluoric corrosive 7.2 x 10 - 4 HNO 2 Nitrous acid 4.0 x 10 - 4 HC 2 H 3 O 2 Acetic acid 1.8 x 10 - 5 [Al(H 2 O) 6 ] 3+ Hydrated aluminum (III) ion 1.4 x10 - 5 HOCl Hypochlorous acid 3.5 x 10 - 8 HCN Hydrocyanic corrosive 6.2 x 10 - 10 NH 4 + Ammonium ion 5.6 x 10 - 10 HOC 6 H 5 Phenol 1.6 x 10 - 10 *The units of K an are mol/L, however are usually discarded. Expanding corrosive quality

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Write the separation response and the relating balance expression for each of the accompanying acids in water. a. H 3 PO 4 b. H 2 PO 4 1- c. HCO 3 1- d. HCN e. Glycine, H 2 NCH 2 COOH f. Acidic corrosive, CH 3 COOH (HC 2 H 3 O 2 ) g. Phenol, C 6 H 5 OH h. Benzoic corrosive, C 6 H 5 COOH

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Write the response and the comparing K b harmony expression for each of the accompanying substances going about as bases in water. a. PO 4 3- g. Glycine, NH 2 CH 2 COOH b. HPO 4 2- h. Ethylamine, CH 3 CH 2 NH 2 c. H 2 PO 4 - I. Aniline, C 6 H 5 NH 2 d. NH 3 j. Dimethylamine, (CH 3 ) 2 NH e. CN - f. Pyridine, C 5 H 5 N

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WEAK ACID CALCULATIONS HA(aq) + H 2 O(l)  H 3 O + (aq) + A - (aq) 2H 2 O(l)  H 3 O + (aq) + OH - (aq) To improve figurings, if % ionization is < 5%, then C HA  [HA] OR [HA] = C HA – [H 3 O + ], Set up pH equilibria estimations in tables as in past equilibria issues .

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Solving Weak Acid Equilibrium Problems List the real species in the arrangement Choose the species that can create H + , and compose adjusted conditions for the responses delivering H + Using the estimations of the balance constants for the responses you have composed, choose which balance will rule in delivering H + Write the balance expression for the prevailing harmony. List the underlying groupings of the species taking an interest in the predominant balance. Characterize the change expected to accomplish harmony; that is, characterize x .. Compose the balance fixations as far as x . Substitute the balance focuses into the harmony expression. Fathom for x the "simple" way; that is , by expecting that [HA] 0 - x  [HA] 0 . Utilize the 5% govern to check whether the estimation is substantial. Figure [H + ] and pH .

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K a Problems For trichlorophenol (HC 6 H 2 Cl 3 O), K a = 1 x 10 - 6 , Calculate the convergences of all species and the pH of a 0.05 M arrangement of trichlorophenol in water. An answer is set up by dissolving 0.56 g benzoic corrosive (C 6 H 5 CO 2 H), K a = 6.4 x 10 - 5 ) in enough water to make 1.0 L of arrangement. Figure [C 6 H 5 CO 2 H]. [C 6 H 5 CO 2 - ], [H + ], [OH - ], and the pH in this arrangement. Compute the pH of an answer containing a blend of 0.050 M HNO 3 and 0.50M HC 2 H 3 O 2 .

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WEAK BASES IONIZATION CONSTANTS B (aq) + H 2 O (l)  BH + (aq) + OH - (aq) K b values at 25 o C are classified or might be computed from K w and K a K w = (K a )(K b ) so K b = K w/K a Where K an is the conjugate corrosive consistent

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K b Problems Thallium (Tl) hydroxide is a solid base utilized as a part of the blend of some natural mixes.

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