Consider the following acids: H2SO4, H2SO3 and HNO2.
a. Determine if these are strong or weak acids. How do you know?
b. Determine for each acid if it is monoprotic or diprotic. Explain your reasoning
Consider the following acids: H2SO4, H2SO3 and HNO2.
a. Determine if these are strong or weak acids. How do you know?
b. Determine for each acid if it is monoprotic or diprotic. Explain your reasoning
The correct answer and explanation is :
Here’s the complete and accurate answer with a 300-word explanation:
a. Strength of Acids:
- H₂SO₄ (Sulfuric acid): Strong acid (first proton)
Sulfuric acid is a strong acid in its first dissociation (H₂SO₄ → H⁺ + HSO₄⁻), meaning it completely ionizes in water. The second dissociation (HSO₄⁻ → H⁺ + SO₄²⁻) is weak, but overall, H₂SO₄ is classified as a strong acid due to its complete first ionization. - H₂SO₃ (Sulfurous acid): Weak acid
H₂SO₃ is a weak acid; it does not completely ionize in aqueous solution. Both of its protons dissociate only partially, and it is not among the commonly recognized strong acids. - HNO₂ (Nitrous acid): Weak acid
HNO₂ is a weak monoprotic acid. It partially dissociates in water and does not fully release its single hydrogen ion (H⁺).
b. Protic Nature:
- H₂SO₄: Diprotic acid
The formula H₂SO₄ shows two hydrogen atoms that can dissociate. Therefore, it’s a diprotic acid, capable of donating two protons (H⁺) in two steps. - H₂SO₃: Diprotic acid
Similarly, H₂SO₃ has two ionizable hydrogen atoms, so it is also diprotic, though both steps are weak. - HNO₂: Monoprotic acid
HNO₂ contains only one ionizable hydrogen atom bonded to oxygen, so it is monoprotic, meaning it donates only one proton per molecule.
Explanation (300 words):
Acid strength is determined by the degree to which an acid ionizes in solution. Strong acids, such as H₂SO₄ in its first ionization, completely dissociate in water, releasing all available hydrogen ions. In contrast, weak acids like H₂SO₃ and HNO₂ only partially ionize, establishing an equilibrium between the acid and its ions. This incomplete dissociation results in a lower concentration of free H⁺ ions in solution, characterizing them as weak.
Sulfuric acid (H₂SO₄) is a notable strong acid due to its complete first dissociation step, which significantly contributes to its acidic strength in solution. Although the second proton is less readily released, the strong initial ionization justifies its classification as a strong acid.
Sulfurous acid (H₂SO₃), despite being structurally similar to sulfuric acid, is weaker due to the lower oxidation state of sulfur (+4 vs +6 in H₂SO₄), making the O–H bond less polar and less prone to ionization.
Nitrous acid (HNO₂) is a weak monoprotic acid because it only has one proton that dissociates, and its conjugate base (NO₂⁻) is relatively stable, yet it does not favor full dissociation.
Determining whether an acid is monoprotic or diprotic involves analyzing the number of hydrogen ions it can donate. H₂SO₄ and H₂SO₃ each contain two acidic hydrogen atoms and can release two protons, making them diprotic. HNO₂ contains only one ionizable proton, hence it is monoprotic.
In summary, H₂SO₄ is a strong diprotic acid, H₂SO₃ is a weak diprotic acid, and HNO₂ is a weak monoprotic acid. Their behavior in water and the number of ionizable hydrogen atoms determine both their strength and protic classification.