Acidic strength of organic compounds and pKa comparisons

55 questions on Acidic strength of organic compounds and pKa comparisons from the General Organic Chemistry II: Acids and Bases chapter: 11 NEET level, 22 JEE Main, 22 JEE Advanced. Each one opens with its answer and solution.

• Which of the following is the strongest acid in water? NEET level
• Which of the following gives the correct order of decreasing acidic strength? NEET level
• Which of the following carboxylic acids is the strongest? NEET level
• Which of the following anions is the weakest base? NEET level
• Which of the following phenols is the most acidic? NEET level
• 2,4,6-Trinitrophenol (picric acid, pKa 0.4) is far more acidic than phenol (pKa 10.0) mainly because NEET level
• Which of the following hydrocarbons is the most acidic? NEET level
• Which of the following is the strongest acid in water? NEET level
• Which of the following is the strongest acid? NEET level
• In aqueous solution the pKa values of the conjugate acids are 4.6 for the anilinium ion (C6H5NH3+) and 10.6 for the methylammonium ion (CH3NH3+). Which statemen... NEET level
• Phenol is a stronger acid than ethanol because NEET level
• Which of the following is the weakest acid? JEE Main level
• Which of the following is the most acidic? JEE Main level
• The pKa values of 4-nitrophenol and 3-nitrophenol in water are 7.15 and 8.35 respectively. The higher acidity of 4-nitrophenol is best explained by JEE Main level
• Which of the following has the most acidic C-H bond? JEE Main level
• Pentane-2,4-dione (pKa 9.0) is a much stronger acid than propanone (pKa 19.3) because JEE Main level
• The pKa values of 4-nitrobenzoic acid and acetic acid in water are 3.44 and 4.76 respectively. Calculate the ratio K_a(4-nitrobenzoic acid) / K_a(acetic acid). ... JEE Main level
• Consider the following amines in aqueous solution, with the pKa of their conjugate acids in brackets: piperidine (11.1), methylamine (10.6), pyridine (5.2), ani... JEE Main level
• Which of the following N-H bonds is the most acidic? JEE Main level
• Which of the following is the correct order of decreasing acidic strength in water? JEE Main level
• Which of the following compounds reacts with sodamide (NaNH2) to give a sodium salt with evolution of ammonia? JEE Main level
• The pKa values of oxalic acid (HOOC-COOH) in water are pK_a1 = 1.25 and pK_a2 = 4.27. The second dissociation is much weaker because JEE Main level
• Which of the following chlorobutanoic acids is the strongest acid? JEE Main level
• Which of the following are stronger acids than phenol (pKa 10.0) in water? JEE Main level
• Which of the following are stronger acids than water (pKa 15.7)? JEE Main level
• The pKa values of acetic acid and benzoic acid are 4.76 and 4.20. Which of the following statements are correct? JEE Main level
• Which of the following hydrocarbons is the most acidic? JEE Main level
• Which of the following does NOT liberate carbon dioxide from aqueous sodium hydrogencarbonate? JEE Main level
• Assertion: 4-Nitrophenol is a stronger acid than 3-nitrophenol. Reason: The -M effect of the nitro group operates from the para position but not from the meta p... JEE Main level
• Assertion: Ethoxide ion is a stronger base than phenoxide ion. Reason: Ethoxide ion is stabilised by resonance. JEE Main level
• Match the acid in List I with its approximate pKa in List II. List I: (P) picric acid, (Q) acetic acid, (R) phenol, (S) ethyne. List II: (1) 25, (2) 0.4, (3) 10... JEE Main level
• Which of the following gives the correct order of decreasing acidity of the C-H bonds in the compounds below? JEE Main level
• The pKa values of acetic acid and phenol in water are 4.76 and 10.0. The ratio K_a(acetic acid)/K_a(phenol) is closest to JEE Main level
• The pKa values in water are nitromethane 10.2 and phenol 10.0. The equilibrium constant for CH3NO2 + C6H5O- <=> CH2NO2- + C6H5OH at 298 K is closest to JEE Advanced level
• The pKa values in water are ethanol 15.9 and ethyne 25. The equilibrium constant for HC#CH + C2H5O- <=> HC#C- + C2H5OH (treating the pKa values as valid for the... JEE Advanced level
• Use pKa values (in water): acetic acid 4.76, phenol 10.0, ethanol 15.9, pentane-2,4-dione 9.0, propanone 19.3. For which of the following reactions is the equil... JEE Advanced level
• How many distinct atoms (including the phenoxide oxygen) can carry the negative charge in the resonance forms of the 4-nitrophenoxide ion? JEE Advanced level
• Use pKa values in water: pentane-2,4-dione 9.0, nitromethane 10.2, propanone 19.3, ethanenitrile 25. Which statements are correct? JEE Advanced level
• Use pKa values: phenol 10.0, phthalimide 8.3, ethanol 15.9, nitromethane 10.2. Which of these are more than 99% ionised in an aqueous solution buffered at pH 13... JEE Advanced level
• At pH 8.15, what is the ratio [anion]/[acid] for 4-nitrophenol (pK_a = 7.15) divided by the same ratio for phenol (pK_a = 10.0)? JEE Advanced level
• Use pKa values of the conjugate acids in water: methylammonium 10.6, imidazolium 7.0, pyridinium 5.2, guanidinium 13.6. At pH 7.4 which species exist predominan... JEE Advanced level
• Which of the following statements are correct? (Use pKa values: 4-nitrophenol 7.15, 3-nitrophenol 8.35, phenol 10.0, 2,4,6-trinitrophenol 0.4, carbonic acid pKa... JEE Advanced level
• Which of the following gives the correct increasing order of acidic strength in water? JEE Advanced level
• The pKa of the anilinium ion is 4.6 at 298 K (K_w = 10^-14). Neglecting the autoionisation of water and the small extent of protonation, the pH of a 0.10 M aque... JEE Advanced level
• Which of the following is the most acidic? JEE Advanced level
• Which is the strongest acid among propanoic acid, prop-2-enoic acid, prop-2-ynoic acid and butanoic acid? JEE Advanced level
• A solution in diethyl ether contains benzoic acid, phenol and naphthalene. It is first shaken with aqueous NaHCO3, the ether layer is separated and then shaken ... JEE Advanced level
• Assertion: Pentane-2,4-dione (pKa 9.0) is a stronger acid than ethyl 3-oxobutanoate (pKa 10.7). Reason: The ester carbonyl is a weaker electron acceptor than th... JEE Advanced level
• Which is the correct order of decreasing acidity of the hydrogens on the carbon marked by the pKa data in these compounds? JEE Advanced level
• Methanoic (formic) acid has pK_a = 3.75 at 298 K. For a 0.10 M aqueous solution, calculate the percentage of the acid that is ionised, using the exact quadratic... JEE Advanced level
• Chloroacetic acid has pK_a = 2.86 at 298 K. The pH of a 0.10 M aqueous solution, calculated with the exact quadratic expression, is closest to JEE Advanced level
• Which of the following statements are correct? JEE Advanced level
• The pKa values in water are 4-nitrobenzoic acid 3.44, benzoic acid 4.20 and 4-methoxybenzoic acid 4.47. The ratio K_a(4-nitrobenzoic acid)/K_a(4-methoxybenzoic ... JEE Advanced level
• Which of the following compounds liberate hydrogen on treatment with sodium metal? JEE Advanced level
• Which of the following pairs have the first acid stronger than the second? JEE Advanced level