Problem 3 - Chemistry and Chemical Reactivity

Question

What are the products of each of the following acid-base reactions? Indicate the acid and its conjugate base and the base and its conjugate acid. (a) \(\mathrm{HNO}_{3}+\mathrm{H}_{2} \mathrm{O} \rightarrow\) (b) \(\mathrm{HSO}_{4}^{-}+\mathrm{H}_{2} \mathrm{O} \rightarrow\) (c) \(\mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{F}^{-} \rightarrow\)

Step-by-Step Solution

Answer

(a) Products: NO₃⁻, H₃O⁺. (b) Products: SO₄²⁻, H₃O⁺. (c) Products: H₂O, HF.

Step 1: Understand the Reaction Type

The given exercise involves identifying the products of acid-base reactions. In an acid-base reaction, an acid donates a proton ( H^+ ) to a base. The products are the conjugate base (from the acid) and the conjugate acid (from the base).

Step 2: Solve Reaction (a)

For the reaction HNO_3 + H_2O \rightarrow: \(HNO_3\) (nitric acid) donates a proton to \(H_2O\). The conjugate base of \(HNO_3\) is \(NO_3^-\), and the conjugate acid formed is \(H_3O^+\). Therefore, the products are \(NO_3^-\) and \(H_3O^+\).

Step 3: Solve Reaction (b)

For the reaction HSO_4^- + H_2O \rightarrow: \(HSO_4^-\) (bisulfate ion) can act as an acid and donate a proton to \(H_2O\). The conjugate base is \(SO_4^{2-}\), and the conjugate acid is \(H_3O^+\). Thus, the products are \(SO_4^{2-}\) and \(H_3O^+\).

Step 4: Solve Reaction (c)

For the reaction H_3O^+ + F^- \rightarrow: \(H_3O^+\) (hydronium ion) acts as an acid and donates a proton to \(F^-\). The conjugate base of \(H_3O^+\) is \(H_2O\), and the conjugate acid formed is \(HF\). Therefore, the products are \(H_2O\) and \(HF\).

Key Concepts

Conjugate Acid

When studying acid-base reactions, it is essential to understand the role of conjugate acids. A conjugate acid is formed when a base gains a proton (H⁺). Think of it as a pair; wherever there is a base, if it accepts a proton, it transforms into its conjugate acid.
For example, in the reaction of the hydronium ion ( H_3O^+ ) with fluoride ion ( F^- ) , when ( F^- ) accepts a proton, it becomes hydrogen fluoride ( HF ) . Hence, ( HF ) serves as the conjugate acid to the base ( F^- ) .
In simpler terms:

• A base gains a proton → Conjugate Acid is formed.
• Example: ( F^- ) + ( H^+ ) → ( HF )

Conjugate Base

In an acid-base reaction, the conjugate base is what remains after an acid has donated a proton. This helps in understanding the idea of conjugate pairs, where acids and their conjugate bases balance each other in the chemical equation.
Let's delve into the example involving nitric acid ( HNO_3 ) reacting with water ( H_2O ) . When ( HNO_3 ) donates a proton, it becomes nitrate ion ( NO_3^- ) , acting as its conjugate base. Here’s a simple breakdown of the process:

• An acid donates a proton → Results in a Conjugate Base.
• Example: ( HNO_3 ) → ( NO_3^- ) + ( H^+ )

Understanding conjugate bases helps us track the flow of protons and predict the resulting products.

Proton Transfer

Proton transfer is the heart of acid-base reactions. It involves the movement of a proton (H⁺) from the acid to the base. This key process is responsible for creating the products of such reactions: the conjugate bases and conjugate acids.
Consider the reaction between the bisulfate ion ( HSO_4^- ) and water ( H_2O ) . Here, ( HSO_4^- ) donates a proton to ( H_2O ) . This proton transfer transforms ( H_2O ) into hydronium ion ( H_3O^+ ) , and ( HSO_4^- ) into sulfate ion ( SO_4^{2-} ) .

• Proton Transfer: The process of an acid donating and a base accepting a proton.
• Key in determining reaction products: ( HSO_4^- ) + ( H_2O ) → ( SO_4^{2-} ) + ( H_3O^+ )

Understanding proton transfer is crucial for grasping how chemical reactions in this category operate.