Rank the following compounds from lowest to highest pKa: benzoic acid, p-hydroxybenzoic acid, p-chlorobenzoic acid, p-nitrobenzoic acid.Select answer from the options belowlowest pKa / p-nitrobenzoic acid < p-chlorobenzoic acid < p-hydroxybenzoic acid < benzoic acid / highest pKalowest pKa / p-hydroxybenzoic acid < benzoic acid < p-chlorobenzoic acid < p-nitrobenzoic acid / highest pKalowest pKa / p-nitrobenzoic acid < p-hydroxybenzoic acid < benzoic acid < p-chlorobenzoic acid / highest pKalowest pKa / p-nitrobenzoic acid < p-chlorobenzoic acid < benzoic acid < p-hydroxybenzoic acid / highest pKa
Question
Rank the following compounds from lowest to highest pKa: benzoic acid, p-hydroxybenzoic acid, p-chlorobenzoic acid, p-nitrobenzoic acid.Select answer from the options belowlowest pKa / p-nitrobenzoic acid < p-chlorobenzoic acid < p-hydroxybenzoic acid < benzoic acid / highest pKalowest pKa / p-hydroxybenzoic acid < benzoic acid < p-chlorobenzoic acid < p-nitrobenzoic acid / highest pKalowest pKa / p-nitrobenzoic acid < p-hydroxybenzoic acid < benzoic acid < p-chlorobenzoic acid / highest pKalowest pKa / p-nitrobenzoic acid < p-chlorobenzoic acid < benzoic acid < p-hydroxybenzoic acid / highest pKa
Solution
The correct order from lowest to highest pKa is: p-nitrobenzoic acid < p-chlorobenzoic acid < benzoic acid < p-hydroxybenzoic acid.
This is because the pKa value is a measure of the acidity of a substance. The lower the pKa value, the stronger the acid. In this case, the nitro group in p-nitrobenzoic acid is a strong electron-withdrawing group, which makes the carboxylic acid more acidic (lower pKa). On the other hand, the hydroxy group in p-hydroxybenzoic acid is an electron-donating group, which makes the carboxylic acid less acidic (higher pKa). The chloro group in p-chlorobenzoic acid is also an electron-withdrawing group, but not as strong as the nitro group, so its pKa is higher than that of p-nitrobenzoic acid but lower than that of benzoic acid.
Similar Questions
Which of the following will have the lowest pKa?Select answer from the options below4-chlorobutanoic acid2-chlorobutanoic acid3-chlorobuanoic acidbutanoic acid
Which of the following carboxylic acids is expected to have the highest pKa?Select answer from the options belowfluoroacetic aciddifluoroacetic acidtrifluoroacetic acidacetic acid
Rank, the following molecules in order of the acid strength, from strongest to weakest.Acetic acid pKa = 4.75Sulphuric acid pKa = 1.92Glycine carboxyl group pKa = 2.3Hydrofluoric acid = pKa 3.3Hydrochloric acid pKa = -9Glycine amine functional group pKa = 9.6
Shown below are 5 molecules and their pKa values. Which compound is the most acidic? Group of answer choicesMolecule DMolecule EMolecule BMolecule CMolecule A
Which of the following compounds is the strongest Brønsted acid?Select answer from the options belowSiH4H3S+
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.