Is the pH greater than, equal to, or less than 7 after the neutralization of each of the following pairs of acids and bases? (b) NH3 and HClO4 (d) (CH3)3N and HOBr

Verified step by step guidance

1. Step 1: Identify the nature of the acid and base in each pair. NH3 is a weak base, and HClO4 is a strong acid. (CH3)3N is a weak base, and HOBr is a weak acid.
2. Step 2: Consider the neutralization reaction. For NH3 and HClO4, the strong acid will completely neutralize the weak base, resulting in a solution that is likely acidic. For (CH3)3N and HOBr, both are weak, so the resulting solution will depend on the relative strengths of the weak acid and weak base.
3. Step 3: Analyze the conjugate acid-base pairs formed. NH3 reacts with HClO4 to form NH4+ and ClO4-. NH4+ is a weak acid, which can contribute to an acidic pH. (CH3)3N reacts with HOBr to form (CH3)3NH+ and OBr-. (CH3)3NH+ is a weak acid, and OBr- is a weak base.
4. Step 4: Evaluate the pH based on the strength of the conjugate acid-base pairs. For NH3 and HClO4, the presence of NH4+ suggests the pH will be less than 7. For (CH3)3N and HOBr, compare the Ka of (CH3)3NH+ and Kb of OBr- to determine if the solution is acidic or basic.
5. Step 5: Conclude the pH comparison. NH3 and HClO4 will result in a pH less than 7 due to the strong acid. For (CH3)3N and HOBr, if the Kb of OBr- is greater than the Ka of (CH3)3NH+, the solution will be basic, otherwise acidic.

Key Concepts

Acid-Base Neutralization

Acid-base neutralization is a chemical reaction where an acid reacts with a base to produce water and a salt. This process typically results in a solution that is closer to neutral pH, which is 7. However, the final pH depends on the strength of the acid and base involved, as well as their concentrations.

Strength of Acids and Bases

Acids and bases can be classified as strong or weak based on their ability to dissociate in water. Strong acids, like HClO4, completely dissociate into ions, while weak bases, like NH3, only partially dissociate. The strength of the acid and base determines the resulting pH after neutralization, influencing whether the solution will be acidic, neutral, or basic.

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH of 7 is considered neutral, below 7 is acidic, and above 7 is basic. Understanding the pH scale is crucial for predicting the outcome of acid-base reactions, as it helps determine whether the resulting solution will be acidic, neutral, or basic after neutralization.