Distinguish strong acids and bases (fully ionized: HCl, HNO3, H2SO4, group 1 hydroxides) from weak ones (partially ionized: organic acids, ammonia), explain that acid-base equilibria favour the weaker conjugate, and compare them experimentally by conductivity, pH and reaction rate.
Tę umiejętność sprawdza 25 zadań wzorowanych na arkuszach IB z lat 2022–2026.
Nitric acid, HNO3, is strong, while nitrous acid, HNO2, is weak. (i) Outline the difference between a strong and a weak acid. (ii) Deduce the Lewis formula and the molecular geometry for the nitrite ion, NO2−. (iii) State the hybridization…
Hydrochloric acid, HCl(aq), and hydroiodic acid, HI(aq), ionize completely in water, whereas propanoic acid, CH3CH2COOH(aq), ionizes only partly. 25.0 cm3 of 0.200 mol dm−3 HCl(aq) was titrated with sodium…
Solutions of hydrobromic acid, HBr, and propanoic acid, CH3CH2COOH, have the same concentration. Which statement is correct? A. Both solutions have the same pH because both acids are monoprotic B. The propanoic acid solution has the lower pH C. The…
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…
The rate of the reaction can be followed by measuring the volume of carbon dioxide collected as time passes. The graph shows the results obtained at 20 °C. (i) Sketch, on the same axes, the curve you would expect if the experiment were repeated with the acid…
Which solution has a pH of 11.0 at 298 K? A. 10−3 mol dm−3 KOH(aq) B. 10−11 mol dm−3 KOH(aq) C. 10−3 mol dm−3 NH3(aq) D. 10−3 mol dm−3 HCl(aq)
What is the main reason why nitric acid has a lower pH than ethanoic acid of the same concentration? A. Nitric acid is an oxidizing agent. B. Nitric acid ionizes to a greater extent in water. C. The conjugate base of nitric acid is stronger than that of…
Which of these aqueous solutions has the highest pH? A. 0.10 mol dm−3 HCl B. 1.0 mol dm−3 NH3 C. 0.10 mol dm−3 KOH D. 1.0 mol dm−3 KOH
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…
The structure of a tartaric acid molecule is shown. (i) State how many hydrogen atoms in a tartaric acid molecule are acidic. (ii) Deduce the structural formula of the conjugate base of tartaric acid. (iii) Predict, giving a reason, whether tartaric acid is a…
Which method can be used to distinguish between nitric acid, HNO3(aq), and ethanoic acid, CH3COOH(aq), of equal concentration? A. measuring the volume of sodium hydroxide solution of known concentration needed to neutralize 20.0 cm3…
Outline how 0.100 mol dm−3 solutions of ethanoic acid and nitric acid could be told apart.
(i) Deduce the ionic equation, including state symbols, for the reaction of hydrogen bromide gas with water. (ii) Calculate the pH of 0.25 mol dm−3 hydrobromic acid. (iii) Explain why a solution of methanoic acid has a higher pH than…
Outline one chemical test, other than the use of an indicator, that can distinguish between the two acids, and state the expected result.
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 <…
Which row correctly describes a weak Brønsted–Lowry acid? A. Ionizes only partially; its conjugate base is relatively strong B. Ionizes almost completely; its conjugate base is relatively strong C. Ionizes almost completely; its conjugate base is very weak D.…
Ethanoic acid and propanone, CH3COCH3, each contain a C=O group, and their molar masses are close. (i) Considering the strongest intermolecular forces in each liquid, explain why propanone boils at a much lower temperature than ethanoic acid.…
Ethanoic acid and propanone, CH3COCH3, both contain a carbonyl group and have similar molar masses. (i) Explain, in terms of the strongest intermolecular forces present in each liquid, why propanone boils at a much lower temperature than ethanoic acid.…
Which substance evaporates easily when pure and gives a strongly conducting solution in water? A. HBr B. KBr C. CH3Br D. NH3
Which substance is highly volatile in its pure state and gives a solution with high electrical conductivity in water? A. CH3Br B. KBr C. H2S D. HBr
(i) Methanal can be reduced. State the name of the organic product formed. (ii) Methanal can also be oxidized to methanoic acid, HCOOH, which is a weak Brønsted–Lowry acid. State the meaning of the term weak Brønsted–Lowry acid.
What happens to the amount of hydrogen ions and to the hydrogen ion concentration when water is added to a solution of ethanoic acid, CH3COOH(aq)? A. n(H+) decreases; [H+] decreases B. n(H+) increases; [H+] decreases C.…
Which 0.10 mol dm−3 aqueous solution has the lowest pH? A. CH3COOH B. HCl C. H2SO4 D. NH4Cl
Equal volumes of 0.050 mol dm−3 ethanoic acid and 0.050 mol dm−3 hydrochloric acid are each titrated with 0.050 mol dm−3 sodium hydroxide solution. Which quantity is the same for the two titrations? A. Initial pH…
Which acid has the weakest conjugate base? A. HF B. CH3COOH C. HNO3 D. NH4+
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