Question

Which of the following salts with a concentration 0.1 \(\mathrm{M}\) will give a basic solution? (a) Ammonium acetate (b) Ammonium chloride (c) Ammonium sulphate (d) Sodium acetate

Short answer

Sodium acetate (d) will give a basic solution.

Step-by-step solution

Identify the Nature of Salts

Explain whether the salt is acidic, basic, or neutral by looking at the constituting acid and base.

Analyze the Cations and Anions

Cations from weak bases (like ammonium, NH4+) tend to make a solution acidic, while anions from weak acids (like acetate, CH3COO-) tend to make solutions basic.

Determine the Basic Salt

Salts from strong bases and weak acids will create a basic solution. Determine which salts fulfill this condition.

Conclude the Basic Salt

After analyzing each option, determine the salt which will create a basic solution at a concentration of 0.1 M.

Key concepts

Salt Hydrolysis

Understanding the concept of salt hydrolysis is crucial when we want to predict the pH of a solution containing a salt.
During hydrolysis, water molecules react with the ions of a dissolved salt. If a salt is formed by the reaction of a strong acid and a weak base, the cations (positive ions) of the weak base will react with water to generate acid, leading to an acidic solution. Conversely, salts derived from weak acids and strong bases will produce hydroxide ions (OH-) when the anions (negative ions) react with water, resulting in a basic solution.
In general, if neither the cation nor the anion reacts significantly with water, the salt is considered to be neutral, yielding a pH close to 7. This reaction is a form of chemical equilibrium, so not all of the ions in a solution will undergo hydrolysis at the same time.

pH of Salt Solutions

Determining the pH of salt solutions requires an analysis of the respective strengths of the acid and base that formed the salt. To predict whether a salt solution will be acidic, basic, or neutral, consider the originating acid and base.
Here's a helpful guideline:

• Salts from strong acids and strong bases typically form neutral solutions.
• Salts from strong acids and weak bases form acidic solutions.
• Salts from weak acids and strong bases form basic solutions.
• Salts from weak acids and weak bases could form either acidic or basic solutions, depending on which reactant is weaker.

As a result, the pH can be above, below, or close to 7, and it is usually determined by the dominant reaction in the hydrolysis process.

Weak Acid and Strong Base Salts

Salts that are the product of a reaction between a weak acid and a strong base are especially interesting, as they characteristically result in a basic solution upon dissolution in water. This is because the anions left from the weak acid will have a higher tendency to accept a proton (H+) and form hydroxide ions (OH-).
For example, sodium acetate (CH₃COONa) is such a salt. Sodium is a cation from a strong base (NaOH), and acetate is an anion from a weak acid (CH₃COOH). Therefore, when sodium acetate dissolves in water, the acetate ions will react with water, increasing the concentration of OH- and pushing the pH of the solution above 7, becoming basic.
These insights help us understand solution property and guide us in chemical synthesis, drug design, and various industrial processes.