Question

Which of the following statement(s) is/are false? (a) \(\mathrm{H}_{3} \mathrm{PO}_{3}\) is a stronger acid than \(\mathrm{H}_{2} \mathrm{SO}_{3}\) (b) in aqueous medium HF is a stronger acid than \(\mathrm{HCl}\) (c) \(\mathrm{HNO}_{3}\) is a stronger acid than \(\mathrm{HNO}_{2}\) (d) \(\mathrm{HClO}_{4}^{3}\) is a weaker acid than \(\mathrm{HClO}_{3}^{2}\)

Short answer

Statements (a), (b), and (d) are false.

Step-by-step solution

Analyzing Statement (a)

The exercise compares \( \mathrm{H}_{3} \mathrm{PO}_{3} \) and \( \mathrm{H}_{2} \mathrm{SO}_{3} \). Sulfurous acid, \( \mathrm{H}_{2} \mathrm{SO}_{3} \), is generally a stronger acid than phosphorous acid, \( \mathrm{H}_{3} \mathrm{PO}_{3} \). This makes statement (a) false because \( \mathrm{H}_{3} \mathrm{PO}_{3} \) is not stronger than \( \mathrm{H}_{2} \mathrm{SO}_{3} \).

Analyzing Statement (b)

This statement compares hydrofluoric acid, \( \mathrm{HF} \), and hydrochloric acid, \( \mathrm{HCl} \), in aqueous medium. Despite the presence of the electronegative fluorine, \( \mathrm{HF} \) is a weaker acid compared to \( \mathrm{HCl} \) when in solution. Hence, this statement is false.

Analyzing Statement (c)

It is known that nitric acid, \( \mathrm{HNO}_{3} \), is a stronger acid than nitrous acid, \( \mathrm{HNO}_{2} \). Therefore, this statement is true; \( \mathrm{HNO}_{3} \) is indeed a stronger acid than \( \mathrm{HNO}_{2} \).

Analyzing Statement (d)

This statement involves a comparison of perchlorate ions, \( \mathrm{HClO}_{4}^{-} \) and chlorate ions, \( \mathrm{HClO}_{3}^{-} \). The structure suggests that \( \mathrm{HClO}_{4} \) is a stronger acid due to extra oxidation strength, making this statement false compared to the conventions presented.

Key concepts

Oxyacid Comparison

Oxyacids are a type of acid that consists of hydrogen, oxygen, and another element. These acids can vary in strength depending on the central atom and the number of oxygen atoms attached. Typically, the more electronegative the central element and the higher the number of oxygen atoms, the stronger the acid. This is because more electronegative elements pull electron density toward themselves, facilitating proton release. Additionally, increased oxygen content helps to stabilize the resulting anion, making proton donation more favorable. For example, sulfur in sulfate and phosphorous in phosphite showcase different acid strengths based on their composition; sulfurous acid tends to be stronger than phosphorous acid.

Acid-Base Properties

Acids and bases are substances that can donate or accept protons, respectively. The strength of an acid is determined by its ability to donate protons to a base. Strong acids completely dissociate in water, donating their protons to water molecules, whereas weak acids only partially dissociate. In aqueous solutions, factors like the solvent's ability to stabilize ions and the inherent electronegativity of the atoms present influence acid strength. For example, between hydrofluoric acid (HF) and hydrochloric acid (HCl), HCl is a stronger acid because, in water, it dissociates completely to give off protons, while HF does so to a much lesser extent.

Inorganic Chemistry

Inorganic chemistry deals with compounds that do not primarily involve carbon-hydrogen bonds, focusing instead on minerals, metals, and gases, among other compounds. In the context of inorganic acids like nitric acid (HNO₃) and nitrous acid (HNO₂), their acid strengths can be evaluated by their chemical structures and oxidation states. In these examples, the presence of a greater number of oxygen atoms in nitric acid facilitates better electron distribution after dissociation, making it a stronger acid than nitrous acid. Such inorganic acid reactions are pivotal in various chemical industrial processes, showing their importance in both fundamental and applied chemistry.

Strong vs Weak Acids

The distinction between strong and weak acids is essential in understanding their behavior and reactivity. A strong acid, like hydrochloric acid (HCl), is characterized by its complete dissociation in aqueous solutions, producing a high concentration of hydrogen ions. In contrast, weak acids like acetic acid (CH₃COOH) do not fully dissociate, thereby yielding fewer hydrogen ions in solution. This extent of dissociation influences the pH of the solution. Factors that contribute to an acid's strength include the stability of the anion formed after losing a proton and the polarity of the bond between hydrogen and the acid's conjugate base. Understanding these properties is crucial for predicting the outcomes of acid-base reactions in various chemical contexts.