Zadanie 3a
Complete the table for Trial 1 and so determine its Ka value. Use section 1 of the data booklet.
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Ka, Kb, pKa and pKb as measures of strength
Interpret Ka, Kb, pKa and pKb values from the data booklet: a larger Ka or smaller pKa means a stronger acid; rank acids and bases by strength and write the Ka or Kb expression for a weak acid or base.
Tę umiejętność sprawdzają 24 zadania wzorowane na arkuszach IB z lat 2022–2026.
Zadania sprawdzające tę umiejętność: 24 Otwórz w wyszukiwarce z filtrami
Zadanie 33
The curve shows the pH during the titration of 25.0 cm3 of a weak monoprotic acid with 0.100 mol dm−3 NaOH. Which value is the pKa of the acid? A. 2.6 B. 6.0 C. 8.2 D. 3.8
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Zadanie 1b
In aqueous solution hydrogen cyanide behaves as a weak acid. (i) Write an equation for the ionization of hydrogen cyanide in water. (ii) Outline two ways in which a solution of 0.050 mol dm−3 HCN could be distinguished experimentally from…
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Zadanie 3b
(i) Outline the way in which ammonia behaves as a Lewis base during the formation of the complex ion [Ag(NH3)2]+(aq). (ii) Determine the pH at 298 K of an aqueous ammonia solution of concentration 0.180 mol dm−3. Use section 1 of the data…
Zadanie 34
The table gives data for four bases at 298 K. Which base has the weakest conjugate acid? A. N2H4 B. C2H5NH2 C. C6H5NH2 D. C5H5N
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Zadanie 1f
The student then used the potassium hydroxide solution standardized in 1c to titrate ethanoic acid, CH3COOH, whose concentration was not known. (i) Neutralizing 25.00 cm3 of the acid required 40.00 cm3 of the standardized…
Zadanie 3f
Hexanoic acid, CH3(CH2)4COOH, is a weak acid. The graph shows how the pH changes during the titration of a 20.0 cm3 aqueous solution of hexanoic acid with aqueous sodium hydroxide. (i) Deduce an expression for the equilibrium constant, K,…
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Zadanie 1e
Hypochlorous acid is a weak acid. In water it is in equilibrium with its conjugate base, the hypochlorite ion, OCl−, which kills microorganisms far less effectively than the acid molecule does. The graph shows what percentage of the dissolved chlorine…
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Zadanie 4a
A small volume of 0.050 mol dm−3 hydrobromic acid is placed in a beaker fitted with a pH probe. Distilled water is then run into the beaker at a constant rate and the pH is logged continuously; the temperature is held at 298 K. (i) Sketch, on…
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Zadanie 3c
Hypochlorous acid, HOCl(aq), has Ka = 2.95 × 10−8. (i) Determine the pH of an aqueous solution of hypochlorous acid of concentration 0.150 mol dm−3. (ii) State one assumption you made in the calculation in (i). (iii) State…
Zadanie 26
At 298 K the pKa of methanoic acid is 3.75 and the pKa of ethanoic acid is 4.76. Which statement is correct for solutions of these acids with the same concentration? A. Ethanoic acid is a stronger acid than methanoic…
Zadanie 29
Which combination is correct for a strong acid and its conjugate base? A. The pKa of the acid is low and the Kb of the conjugate base is low B. The pKa of the acid is low and the Kb of the…
Zadanie 5a
In a titration, 25.00 cm3 of a 0.120 mol dm−3 solution of a weak monoprotic organic acid, HA, was neutralized by adding sodium hydroxide solution, NaOH(aq), from a burette. The pH curve obtained is shown. (i) Determine the…
- Materiał graficzny
Zadanie 19b
A liquid medicine is buffered with carbonate ions and hydrogencarbonate ions. It contains 0.0120 mol dm−3 carbonate ions and 0.0300 mol dm−3 hydrogencarbonate ions. Ka (hydrogencarbonate ion) = 4.80 × 10−11.…
Zadanie 25
Using the data in the table, which conjugate base is the weakest? A. CN− B. CH3COO− C. NO2− D. CHCl2COO−
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Zadanie 27
A 20.0 cm3 sample of a weak monoprotic acid, HA, was titrated with sodium hydroxide solution of concentration 0.100 mol dm−3. What is the pKb of the conjugate base of HA, A−? A. 3 B. 5 C. 9 D. 11
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Zadanie 24
The table shows the acid dissociation constants of two substances. A third substance, methanol, does not ionize in water. Which sequence shows the aqueous solutions, all of equal concentration, in order of increasing electrical conductivity? A. methanol <…
- Tabela do uzupełnienia
Zadanie 1d
Ethanoic acid is a weak monobasic acid. The acid dissociation constant of ethanoic acid at 298 K is Ka = 1.74 × 10−5. (i) A student dissolved a sample of ethanoic acid in water and made the solution up to 2.00 dm3. Exactly 19.4…
Zadanie 28
A 0.010 mol dm−3 solution of a weak acid has Ka = 1.0 × 10−6. What is its pH? A. 2 B. 4 C. 6 D. 8
Zadanie 4c
The base dissociation constant of methylamine at 298 K is Kb = 4.4 × 10−4. (i) Calculate the concentration of hydroxide ions in a methylamine solution with pH = 11.6. Use sections 1 and 2 of the data booklet. (ii) Calculate the concentration, in…
Zadanie 7a
(i) State why ammonia can act as a Lewis base. (ii) Calculate the pH of a 2.50 × 10−2 mol dm−3 aqueous solution of ammonia. pKb = 4.75 at 298 K. (iii) Justify whether a 1.0 dm3 solution made by mixing 0.30 mol NH3…
Zadanie 25
What is the strongest base in the equilibrium below? NH3 + H2O ⇌ NH4+ + OH− Kb = 1.8 × 10−5 A. NH3 B. H2O C. NH4+ D. OH−
Zadanie 26
A weak acid is titrated with sodium hydroxide solution. Which value of pKa can be estimated from this titration curve? A. 8.4 B. 4.2 C. 2.6 D. 12.3
- Materiał graficzny
Zadanie 1c
A 0.50 mol dm−3 solution of ammonium chloride is prepared. (i) Calculate the pH of an ammonium chloride solution with [H3O+] = 1.68 × 10−5 mol dm−3. Use section 1 of the data booklet. (ii) Write the equation for the…
- Materiał graficzny