Problem 33 - Chemistry The Central Science In Si Units

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 is diprotic. (b) False: \\(\text{HCl}\\) is a strong acid. (c) False: Methanol is an alcohol, not a base.

Step 1: Analyzing Statement (a)

Sulfuric acid, denoted as \( ext{H}_2 ext{SO}_4\), is not a monoprotic acid. A monoprotic acid is an acid that donates only one proton or hydrogen atom per molecule to an aqueous solution. Sulfuric acid, however, is a diprotic acid, which means it can donate two protons per molecule. Therefore, statement (a) is false because sulfuric acid can donate two hydrogen ions.

Step 2: Evaluating Statement (b)

Hydrochloric acid, represented by \( ext{HCl}\), is a strong acid. Strong acids completely dissociate into their ions in water. In the case of \( ext{HCl}\), it dissociates completely into \( ext{H}^+\) and \( ext{Cl}^-\) ions. Therefore, statement (b) is false because hydrochloric acid is not a weak acid.

Step 3: Assessing Statement (c)

Methanol, with the chemical formula \( ext{CH}_3 ext{OH}\), is an alcohol, not a base. Bases are substances that can accept hydrogen ions (protons) or donate a pair of valence electrons to form a bond. Methanol is primarily solvent and alcohol, and does not typically exhibit the characteristics of a base. Therefore, statement (c) is false.

Key Concepts

Diprotic Acid

Diprotic acids are fascinating because they can donate two protons (hydrogen ions) per molecule in a solution. This is a unique property because most acids are monoprotic, meaning they donate just one proton. Sulfuric acid (\(\text{H}_2\text{SO}_4\)) is a classic example of a diprotic acid. In the first step of ionization, it donates one proton, creating hydronium ions (\(\text{H}_3\text{O}^+\)) and hydrogen sulfate ions (\(\text{HSO}_4^-\)). In a secondary ionization step, it can further donate another proton from \(\text{HSO}_4^-\) to form sulfate ions (\(\text{SO}_4^{2-}\)). This ability to donate two protons makes diprotic acids more versatile in chemical reactions compared to monoprotic acids.

• In aqueous solutions, a diprotic acid can undergo two dissociation steps.
• Understanding each dissociation stage is crucial because it affects the overall acidity and behavior of the acid in solutions.
• The extent of ionization in each step can vary, influencing pH levels and other properties of the solution.

Diprotic acids are essential in various chemical processes, including industrial manufacturing and biochemical cycles, underscoring their substantial role in both environmental and human-made contexts.

Strong Acid

A strong acid is characterized by its ability to dissociate completely in aqueous solutions. Hydrochloric acid (\(\text{HCl}\)) embodies this property famously. In water, \(\text{HCl}\) separates entirely into \(\text{H}^{+}\) and \(\text{Cl}^{-}\) ions.
This complete ionization means that the concentration of hydrogen ions (\(\text{H}^{+}\)) is equal to the initial concentration of the acid, making it very acidic.
It is crucial to differentiate strong acids from weak acids, which only partially ionize in solutions, equilibrating to form a mix of undissociated and dissociated ions.

• Strong acids are excellent at conducting electricity due to the abundance of ions formed in solution.
• With complete ionization, strong acids like \(\text{HCl}\) have significantly lower pH values compared to weak acids.
• In chemical reactions, strong acids tend to react with bases to form salt and water in neutralization reactions.

Their pronounced reactivity and complete dissociation make strong acids indispensable in industrial and laboratory applications, where they are used to drive reactions, etch metals, and synthesize chemical compounds.

Chemical Properties of Alcohols

Alcohols, like methanol (\(\text{CH}_3\text{OH}\)), have unique chemical properties that distinguish them from acids and bases. They consist of a hydroxyl group (\(\text{-OH}\)) bonded to a carbon atom. Although part of their structure resembles water, they do not behave as bases. Instead, alcohols serve primarily as solvents, playing a critical role in both synthetic chemistry and industrial processes.
Alcohols differ from bases as they do not accept protons nor donate electron pairs to form new bonds. While they have a hydrogen atom, they do not typically dissociate to release \(\text{H}^+\) ions like an acid would.
The reactivity of alcohols is influenced mainly by the hydroxyl functional group, which can participate in various reactions, including hydrogen bonding and dehydration processes.

• Alcohols are often used as intermediate compounds in chemical synthesis.
• They exhibit specific boiling points, which are generally higher than hydrocarbons due to hydrogen bonding.
• In oxidation reactions, alcohols can transform into aldehydes or ketones, and eventually into carboxylic acids.

Due to their versatile chemical nature, alcohols serve as essential components in pharmaceuticals, fuels, and personal care products, highlighting their broad spectrum of utility in science and industry.