Problem 33 - Chemistry: The Central Science

Question

State whether each of the following statements is true or false. Justify your answer in each case. (a) Sulfuric acid is a monoprotic acid. (b) \(\mathrm{HCl}\) is a weak acid. (c) Methanol is a base.

Step-by-Step Solution

Answer

(a) False. Sulfuric acid (\(\mathrm{H_2SO_4}\)) is a diprotic acid, as it can donate two protons (\(\mathrm{H^+}\)) per molecule. (b) False. Hydrochloric acid (\(\mathrm{HCl}\)) is a strong acid, as it dissociates completely in water. (c) False. Methanol (\(\mathrm{CH_3OH}\)) is an alcohol, not a base, as it does not have the properties of a typical base.

Step 1: a) Sulfuric acid is a monoprotic acid.

This statement is false. A monoprotic acid is an acid that can donate only one proton (\(\mathrm{H^+}\)) per molecule when it dissociates in water. Sulfuric acid (\(\mathrm{H_2SO_4}\)) is a diprotic acid as it can donate two protons (\(\mathrm{H^+}\)) per molecule. The dissociation of sulfuric acid in water can be written as: \[ \mathrm{H_2SO_4 \rightarrow H^+ + HSO_4^-} \] \[ \mathrm{HSO_4^- \rightarrow H^+ + SO_4^{2-}} \] Since sulfuric acid can donate two protons, it is not a monoprotic acid and this statement is false.

Step 2: b) \(\mathrm{HCl}\) is a weak acid.

This statement is false. An acid's strength is determined by its ability to dissociate completely into its ions in water. Hydrochloric acid (\(\mathrm{HCl}\)) is a strong acid because it dissociates completely in water. The dissociation of \(\mathrm{HCl}\) in water can be written as: \[ \mathrm{HCl \rightarrow H^+ + Cl^-} \] Since \(\mathrm{HCl}\) dissociates completely into its ions, it is a strong acid, not a weak acid. Therefore, this statement is false.

Step 3: c) Methanol is a base.

This statement is false. Methanol (\(\mathrm{CH_3OH}\)) is an alcohol, not a base. A base is a substance that can accept protons (\(\mathrm{H^+}\)) or donate electron pairs. Methanol does not have the properties of a typical base, as it does not have a basic functional group (such as an amine group) that can donate electron pairs or accept protons. Methanol's structure is as follows: \[ \mathrm{CH_3 - OH} \] Although the oxygen atom in methanol has a pair of non-bonded electrons, it does not have a significant tendency to donate electron pairs or accept protons, thus it cannot be considered as a base. Therefore, this statement is false.