Choose from the conjugate acid–base pairs HSO4- >SO42-, HF>F-, and NH4+>NH3 to complete the following equation with the pair that gives an equilibrium constant Kc 7 1. _____ + NO2 - S _____ + HNO2

Verified step by step guidance

1. Step 1: The given equation is a typical acid-base reaction. In this type of reaction, an acid reacts with a base to form a conjugate base and a conjugate acid. The general form of an acid-base reaction is: Acid + Base -> Conjugate Base + Conjugate Acid.
2. Step 2: The equilibrium constant Kc > 1 indicates that the reaction favors the products. This means that the acid-base pair we choose should be such that the acid is stronger than the base. A stronger acid will have a weaker conjugate base and will therefore favor the formation of products.
3. Step 3: Among the given pairs, HSO4- >SO42-, HF>F-, and NH4+>NH3, we need to identify the pair where the acid is stronger than the base. We can use the pKa values to determine the strength of the acids. The acid with the lowest pKa value is the strongest.
4. Step 4: The pKa values for HSO4-, HF, and NH4+ are approximately 2, 3.2, and 9.2 respectively. Therefore, HSO4- is the strongest acid among the given options.
5. Step 5: Therefore, the correct pair to complete the equation is HSO4- >SO42-. The completed equation will be: HSO4- + NO2- -> SO42- + HNO2.

Key Concepts

Conjugate Acid-Base Pairs

Conjugate acid-base pairs consist of two species that differ by the presence of a proton (H+). When an acid donates a proton, it forms its conjugate base, while a base that accepts a proton forms its conjugate acid. Understanding these pairs is crucial for predicting the direction of acid-base reactions and the equilibrium established in a chemical equation.

Equilibrium Constant (Kc)

The equilibrium constant (Kc) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. A Kc value greater than 1 indicates that products are favored, while a value less than 1 suggests that reactants are favored. This concept is essential for determining which conjugate acid-base pair will shift the equilibrium in the desired direction.

Acid-Base Strength

The strength of an acid or base is determined by its ability to donate or accept protons, respectively. Strong acids completely dissociate in solution, while weak acids only partially dissociate. This concept is important when selecting the appropriate conjugate acid-base pair, as the strength influences the position of equilibrium and the value of Kc in the reaction.