Concept explainers
Interpretation: In the given molecular model, an aqueous solution of two conjugate acid-base pairs
Concept introduction: Strong acid can donate its proton. Strong acid/base will have weaker conjugate base/acid. The equilibrium constant
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CHEMISTRY:MOLECULAR...(LL) W/ALEKS
- For conjugate acidbase pairs, how are Ka and Kb related? Consider the reaction of acetic acid in water CH3CO2H(aq)+H2O(l)CH3CO2(aq)+H3O+(aq) where Ka = 1.8 105 a. Which two bases are competing for the proton? b. Which is the stronger base? c. In light of your answer to part b. why do we classify the acetate ion (CH3CO2) as a weak base? Use an appropriate reaction to justify your answer. In general, as base strength increases, conjugate acid strength decreases. Explain why the conjugate acid of the weak base NH3 is a weak acid. To summarize, the conjugate base of a weak acid is a weak base and the conjugate acid of a weak base is a weak acid (weak gives you weak). Assuming Ka for a monoprotic strong acid is 1 106, calculate Kb for the conjugate base of this strong acid. Why do conjugate bases of strong acids have no basic properties in water? List the conjugate bases of the six common strong acids. To tie it all together, some instructors have students think of Li+, K+, Rb+, Cs+, Ca2+, Sr2+, and Ba2+ as the conjugate acids of the strong bases LiOH, KOH. RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2. Although not technically correct, the conjugate acid strength of these cations is similar to the conjugate base strength of the strong acids. That is, these cations have no acidic properties in water; similarly, the conjugate bases of strong acids have no basic properties (strong gives you worthless). Fill in the blanks with the correct response. The conjugate base of a weak acid is a_____base. The conjugate acid of a weak base is a_____acid. The conjugate base of a strong acid is a_____base. The conjugate acid of a strong base is a_____ acid. (Hint: Weak gives you weak and strong gives you worthless.)arrow_forwardThe hydrogen phthalate ion, C8HsO4, is a weak acid with Ka = 3.91 106. C8H5O4(aq)+H2O(l)C8H4O42(aq)+H3O+(aq) What is the pH of a 0.050 M solution of potassium hydrogen phthalate. KC8H5O4? Note: To find the pH for a solution of the anion, we must take into account that the ion is amphiprotic. It can be shown that, for most cases of amphiprotic ions, the H3O+ concentration is [H3O+]=Ka1Ka2 For phthalic acid, C8H6O4 is Ka1 is 1.12 103, and Ka2 is 3.91 106.arrow_forwardMost naturally occurring acids are weak acids. Lactic acid is one example. CH3CH(OH)CO2H(s)+H2O(l)H3O+(aq)+CH3CH(OH)CO2(aq) If you place some lactic acid in water, it will ionize to a small extent, and an equilibrium will be established. Suggest some experiments to prow that this is a weak acid and that the establishment of equilibrium is a reversible process.arrow_forward
- 5) Find the concentration of H30*(aq) in a 1.75 M solution of lactic acid, HC3H5O3, at 25°C. Ka= 1.38 x 10*. 6) Write the equilibrium expression for the ionization of HOI, and calculate the concentration of HOI(aq) in solution if [H3O*]=2.3 x 10° M and pKa = 10.7 at 25°C.arrow_forwardConsider this reaction: CH3Hgl + HCl = CH3H&CI + HI Which is the correct prediction and explanation about the equilibrium constant, K, for this reaction? OK> 1, because I is a harder base than Cl. OK 1, because Cl is a harder base than I. OK< 1, because Cl is a harder base than I.arrow_forwardYou are on a new planet and discover a substance, Z2O that undergoes autoionization just like water on Earth. Z2O + Z2O ⇌ Z3O+ + OZ– Through a series of experiments, you determine the equilibrium constant (Kx) for this autoionization reaction at various temperatures. The value of Keq at 26.8ºC is 6.9 x 10-14. What is the pZ of the pure substance at this temperature? (pZ = -log(Z3O+) Report your answer to the hundreths placearrow_forward
- Swimming pool disinfectants produce hypochlorous acid upon dissolution. The weak acid ionizes as follows: HClO (aq) ⇄ H+ (aq) + ClO‒ (aq) Ka=3.0 x 10 ‒8 As strong oxidizing agents, both acid and its conjugate base kill bacteria. However, too high [HClO] is irritating to swimmers’ eyes and too high [ClO‒] will cause the ions to decompose in sunlight. The recommended pH to circumvent both problems is 7.8. Determine the ratio of the weak acid and its conjugate base at this pH.arrow_forwardDetermine the equilibrium constant for the following reaction: Ca(OH)2(s) + 2 H+(aq) --> Ca2+(aq) + 2 H2O(l) given the chemical reactions below. Ca(OH)2(s) --> Ca2+(aq) + 2 OH-(aq) K = 6.5 X 10-6 H2O(l) --> H+(aq) + OH-(aq) K = 1.0 X 10-14arrow_forwardHA, a weak acid, also forms the ion HA, in solution. The reaction is HA(aq) + A (aq) = HA, (aq) The weak acid has K, = 8.64 × 10-7 and the reaction has K = 3.80. Calculate the concentrations of A, H*, and HA, in a 1.00 M solution of HA. [A¯] = M [H*] = M [HA,] = Marrow_forward
- 9. We prepared a solution containing 1.0 mol.L' HF and 1.0 mol.L·' C,H3OH. The K, of hydrofluoric acid and phenol are 7.2 x 104 and 1.6 x 10-10 respectively. What is the pH of this solution? (Hint: find which acid is strongest and make the appropriate assumptions) b. What is the concentration of C,H;O¯ at equilibrium? а.arrow_forwardA monoprotic weak acid, HA, dissociates in water according to the reaction HA(aq) + H₂O(1) ⇒ H₂O* (aq) + A¯(aq) The equilibrium concentrations of the reactants and products are [HA] = 0.100 M, [H3O+] = 3.00 × 10−4 M, and [A-] = 3.00 × 10-4 M. Calculate the Ką value for the acid HA. Ka =arrow_forwardWhat is one acidifying process that produces H+ ions?arrow_forward
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