This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Here are the solutions to questions 16 through 23: 16. Find the correct statement: A. Longer hydrogen bonds are weaker and more electrostatic in nature than shorter hydrogen bonds. (Longer bonds are weaker, but the statement about "more electrostatic" is debatable as stronger bonds also have significant electrostatic character.) B. Hydrogen bond is a result of a strong interaction between a hydrogen atom bound to a very electropositive element and a lone electron pair on a neighbouring atom. (Incorrect. Hydrogen is bound to a very electronegative* element, not electropositive.) C. A short hydrogen bond can be expected to have a high degree of electrostatic character because the element with lone pairs has high electronegativity. (This is correct. The high electronegativity of the acceptor atom (with lone pairs) enhances the electrostatic attraction to the partially positive hydrogen, contributing to the strength and electrostatic nature of the bond.) D. None of the options. The correct answer is C. 17. Arrhenius defined an acid as: A. a species that can donate a proton. (Bronsted-Lowry definition) B. a species that can accept a proton. (Bronsted-Lowry definition of a base) C. a source of OH⁻ ions in water. (Arrhenius definition of a base) D. a source of H⁺ ions in water. (Arrhenius definition of an acid) The correct answer is D. 18. In the Bronsted-Lowry system, a base is defined as: A. a proton donor. (This is a Bronsted-Lowry acid) B. a hydroxide donor. (This is an Arrhenius base) C. an electron-pair acceptor. (This is a Lewis acid) D. a water-former. (Not a definition of a base) E. a proton acceptor. (This is a Bronsted-Lowry base) The correct answer is E. 19. In the equation: HF + H_2O H_3O^+ + F^- Step 1: Identify proton transfer. HF donates a proton to H_2O. H_2O accepts a proton from HF. Step 2: Classify reactants and products. HF is an acid (proton donor). H_2O is a base (proton acceptor). F^- is the conjugate base of HF. H_3O^+ is the conjugate acid of H_2O. A. H_2O is a base and HF is its conjugate acid. (Incorrect) B. H_2O is an acid and HF is the conjugate base. (Incorrect) C. HF is an acid and F^- is its conjugate base. (Correct) D. HF is a base and H_3O^+ is its conjugate acid. (Incorrect) The correct answer is C. 20. For the system shown here: HOBr + OH^- H_2O + OBr^- Bronsted would classify the base species as: Step 1: Identify proton transfer. HOBr donates a proton to OH^-. OH^- accepts a proton from HOBr. Step 2: Classify reactants and products. HOBr is an acid. OH^- is a base. H_2O is the conjugate acid of OH^-. OBr^- is the conjugate base of HOBr. Step 3: Identify all base species. The base species are the proton acceptors: OH^- (reactant) and OBr^- (product, which is the conjugate base). The correct answer is C. OBr^- and OH^-. 21. Which is the strongest acid? A. HClO_4 (Perchloric acid) B. HClO_3 (Chloric acid) C. HClO_2 (Chlorous acid) D. HF (Hydrofluoric acid) For oxoacids with the same central atom, acidity increases with the number of oxygen atoms. Thus, HClO_4 > HClO_3 > HClO_2. HClO_4 is one of the strongest known acids. HF is a weak acid. Therefore, HClO_4 is the strongest among the given options. The correct answer is A. HClO_4. 22. Which of these species is probably the weakest acid? A. H_3PO_4 (Phosphoric acid, K_a1 = 7.5 × 10^-3) B. H_2PO_4^- (Dihydrogen phosphate ion, K_a2 = 6.2 × 10^-8) C. HPO_4^2- (Hydrogen phosphate ion, K_a3 = 4.8 × 10^-13) D. HNO_3 (Nitric acid, a strong acid) Acidity decreases significantly with each successive deprotonation of a polyprotic acid. HNO_3 is a strong acid. Comparing the phosphoric acid species, H_3PO_4 is stronger than H_2PO_4^-, which is stronger than HPO_4^2-. Therefore, HPO_4^2- is the weakest acid among the choices. The correct answer is C. HPO_4^2-. 23. Consider the neutralization reactions between the following acid-base pairs in dilute aqueous solutions: (1) CH_3COOH + NaOH → This is a reaction between a weak acid (acetic acid) and a strong base (sodium hydroxide). The products are a salt (sodium acetate) and water. CH_3COOH(aq)