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Problem 101
Which, if any, of the following statements are true? (a) The stronger the base, the smaller the pKb. (b) The stronger the base, the larger the pKb. (c) The stronger the base, the smaller the Kb. (d) The stronger the base, the larger the Kb. (e) The stronger the base, the smaller the pKa of its conjugate acid. (f) The stronger the base, the larger the pKa of its conjugate acid.
Problem 102b
Predict how each molecule or ion would act, in the Brønsted-Lowry sense, in aqueous solution by writing 'acid,' 'base,' 'both,' or 'neither' on the line provided. (b) Prozac
Problem 103
Calculate the pH of a solution made by adding 2.50 g of lithium oxide 1Li2O2 to enough water to make 1.500 L of solution.
- What is the pH of a solution that is 2.5 * 10^-9 M in NaOH? Does your answer make sense? What assumption do we normally make that is not valid in this case?
Problem 105
- Oxalic acid H2C2O4 is a diprotic acid. By using data in Appendix D as needed, determine whether each of the following statements is true: (a) H2C2O4 can serve as both a Brønsted–Lowry acid and a Brønsted–Lowry base. (b) C2O4²⁻ is the conjugate base of HC2O4⁻. (c) An aqueous solution of the strong electrolyte KHC2O4 will have a pH of 6 or 7.
Problem 106
- Succinic acid (H2C4H6O4), which we will denote H2Suc, is a biologically relevant diprotic acid with the structure shown below. At 25 °C, the acid-dissociation constants for succinic acid are Ka1 = 6.9 * 10^-5 and Ka2 = 2.5 * 10^-6. (a) Determine the pH of a 0.32 M solution of H2Suc at 25 °C, assuming that only the first dissociation is relevant. (b) Determine the molar concentration of Suc2- in the solution in part (a). (c) Is the assumption you made in part (a) justified by the result from part (b)?
Problem 107
Problem 108a
Butyric acid is responsible for the foul smell of rancid butter. The pKa of butyric acid is 4.84. (a) Calculate the pKb for the butyrate ion.
Problem 108c
Butyric acid is responsible for the foul smell of rancid butter. The pKa of butyric acid is 4.84. (c) Calculate the pH of a 0.050 M solution of sodium butyrate.
Problem 109
Arrange the following 0.10 M solutions in order of increasing acidity: (i) NH4NO3, (ii) NaNO3, (iii) CH3COONH4, (iv) NaF, (v) CH3COONa.
Problem 111
The following observations are made about a diprotic acid H2A: (i) A 0.10 M solution of H2A has pH = 3.30. (ii) A 0.10 M solution of the salt NaHA is acidic. Which of the following could be the value of pKa2 for H2A: (i) 3.22, (ii) 5.30, (iii) 7.47, or (iv) 9.82?
- Many moderately large organic molecules containing basic nitrogen atoms are not very soluble in water as neutral molecules, but they are frequently much more soluble as their acid salts. Assuming that the pH in the stomach is 2.5, indicate whether each of the following compounds would be present in the stomach as the neutral base or in the protonated form: nicotine, Kb = 7 * 10-7; caffeine, Kb = 4 * 10-14; strychnine, Kb = 1 * 10-6; quinine, Kb = 1.1 * 10-6.
Problem 112
Problem 113a
The amino acid glycine (H2N–CH2–COOH) can participate in the following equilibria in water:
H2N–CH2–COOH + H2O ⇌ H2N–CH2–COO– + H3O+ Ka = 4.3 × 10-3
H2N–CH2–COOH + H2O⇌ +H3N–CH2–COOH + OH- Kb = 6.0 × 10-5
(a) Use the values of Ka and Kb to estimate the equilibrium constant for the intramolecular proton transfer to form a zwitterion: H2N–CH2–COOH ⇌ +H3N–CH2–COO–
Problem 113b
The amino acid glycine (H2N–CH2–COOH) can participate in the following equilibria in water:
H2N–CH2–COOH + H2O ⇌ H2N–CH2–COO– + H3O+ Ka = 4.3 × 10-3
H2N–CH2–COOH + H2O⇌ +H3N–CH2–COOH + OH- Kb = 6.0 × 10-5
(b) What is the pH of a 0.050 M aqueous solution of glycine?
- The pKb of water is _______. (a) 1 (b) 7 (c) 14 (d) not defined (e) none of the above
Problem 114
- Calculate the number of H3O+ ions in 1.0 mL of pure water at 25 °C.
Problem 115
- How many milliliters of concentrated hydrochloric acid solution (36.0% HCl by mass, density = 1.18 g/mL) are required to produce 10.0 L of a solution that has a pH of 2.05?
Problem 116
Problem 117a
Atmospheric CO2 levels have risen by nearly 20% over the past 40 years from 320 ppm to 400 ppm. (a) Given that the average pH of clean, unpolluted rain today is 5.4, determine the pH of unpolluted rain 40 years ago. Assume that carbonic acid 1H2CO32 formed by the reaction of CO2 and water is the only factor influencing pH. CO21g2 + H2O1l2 Δ H2CO31aq2
Problem 119
At 50 °C, the ion-product constant for H2O has the value Kw = 5.48 * 10-14. (a) What is the pH of pure water at 50 °C? (b) Based on the change in Kw with temperature, predict whether ΔH is positive, negative, or zero for the autoionization reaction of water: 2 H2O1l2 Δ H3O+1aq2 + OH-1aq2
Problem 180b
Butyric acid is responsible for the foul smell of rancid butter. The pKa of butyric acid is 4.84. (b) Calculate the pH of a 0.050 M solution of butyric acid.