Chapter 18: Problem 116
What determines whether an aqueous solution of a salt will be acidic, basic, or neutral? Give an example of each type of salt.
Short Answer
Expert verified
The pH of a salt solution is determined by the strengths of its parent acid and base. Examples: Neutral (NaCl), Acidic (NH4Cl), Basic (NaCH3COO).
Step by step solution
01
- Identify Salt Components
Analyze the salt to see from which acid and base the salt is derived. The nature (strong or weak) of the parent acid and base will help determine the pH of the salt solution.
02
- Determine the Parent Acid and Base
For a given salt, identify its constituent acid and base. For example, for sodium chloride (NaCl), the parent acid is hydrochloric acid (HCl), and the parent base is sodium hydroxide (NaOH).
03
- Assess Acid and Base Strengths
Evaluate the strengths of the parent acid and base. A strong acid and strong base will result in a neutral salt. A strong acid and a weak base will result in an acidic salt and a weak acid and strong base will cause the salt to be basic.
04
- Classify the Salt
Based on the strengths, classify the salt: - Neutral salts: Strong acid + Strong base (e.g., NaCl). - Acidic salts: Strong acid + Weak base (e.g., NH4Cl). - Basic salts: Weak acid + Strong base (e.g., NaCH3COO).
05
- Provide Examples
Provide examples of each type of salt and their corresponding acid/base pairs: - Neutral salt: NaCl (from HCl and NaOH). - Acidic salt: NH4Cl (from HCl and NH3). - Basic salt: NaCH3COO (from CH3COOH and NaOH).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
acidic salts
Acidic salts are formed from the reaction between a strong acid and a weak base. The resulting salt will produce a solution with a pH less than 7 when dissolved in water. The reason lies in hydrolysis; the weak base is not able to fully neutralize the strong acid, leaving behind some acidic properties.
An example of an acidic salt is ammonium chloride (NH4Cl). In this case, hydrochloric acid (HCl) is the strong acid, and ammonia (NH3) is the weak base. When NH4Cl dissolves in water, it dissociates into ammonium ions (NH4+) and chloride ions (Cl-). The NH4+ ions hydrolyze to produce hydrogen ions (H+), making the solution acidic.
An example of an acidic salt is ammonium chloride (NH4Cl). In this case, hydrochloric acid (HCl) is the strong acid, and ammonia (NH3) is the weak base. When NH4Cl dissolves in water, it dissociates into ammonium ions (NH4+) and chloride ions (Cl-). The NH4+ ions hydrolyze to produce hydrogen ions (H+), making the solution acidic.
- Example: NH4Cl (from HCl and NH3)
- Reaction: NH4Cl → NH4+ + Cl-
- Hydrolysis: NH4+ + H2O → NH3 + H3O+
basic salts
Basic salts originate from the reaction of a weak acid with a strong base. These salts yield a solution with a pH greater than 7, indicating a basic environment. The weak acid cannot completely neutralize the strong base, so some basic properties remain.
Sodium acetate (NaCH3COO) is a classic example of a basic salt. Originating from acetic acid (CH3COOH), a weak acid, and sodium hydroxide (NaOH), a strong base, this salt dissociates in water to form sodium ions (Na+) and acetate ions (CH3COO-). The acetate ions undergo hydrolysis to produce hydroxide ions (OH-), making the solution basic.
Sodium acetate (NaCH3COO) is a classic example of a basic salt. Originating from acetic acid (CH3COOH), a weak acid, and sodium hydroxide (NaOH), a strong base, this salt dissociates in water to form sodium ions (Na+) and acetate ions (CH3COO-). The acetate ions undergo hydrolysis to produce hydroxide ions (OH-), making the solution basic.
- Example: NaCH3COO (from CH3COOH and NaOH)
- Reaction: NaCH3COO → Na+ + CH3COO-
- Hydrolysis: CH3COO- + H2O → CH3COOH + OH-
neutral salts
Neutral salts are produced from the reaction of a strong acid and a strong base. The resulting solution will have a pH close to 7, making it neutral. In this case, both the acid and base completely neutralize each other, leaving no excess hydrogen or hydroxide ions.
Sodium chloride (NaCl) is a well-known example of a neutral salt derived from the reaction of hydrochloric acid (HCl) and sodium hydroxide (NaOH). When NaCl dissolves in water, it dissociates into sodium ions (Na+) and chloride ions (Cl-). Neither of these ions reacts with water to affect the pH.
Sodium chloride (NaCl) is a well-known example of a neutral salt derived from the reaction of hydrochloric acid (HCl) and sodium hydroxide (NaOH). When NaCl dissolves in water, it dissociates into sodium ions (Na+) and chloride ions (Cl-). Neither of these ions reacts with water to affect the pH.
- Example: NaCl (from HCl and NaOH)
- Reaction: NaCl → Na+ + Cl-
strength of acids and bases
The strength of acids and bases play a crucial role in determining the pH of salt solutions. The strength is based on their ability to dissociate in water:
• Strong acids and bases dissociate completely in water, producing ions that can fully neutralize their counterparts.
Examples of strong acids include hydrochloric acid (HCl) and sulfuric acid (H2SO4). Examples of strong bases are sodium hydroxide (NaOH) and potassium hydroxide (KOH).
• Weak acids and bases only partially dissociate in water, leaving some unreacted molecules behind.
• Strong acids and bases dissociate completely in water, producing ions that can fully neutralize their counterparts.
Examples of strong acids include hydrochloric acid (HCl) and sulfuric acid (H2SO4). Examples of strong bases are sodium hydroxide (NaOH) and potassium hydroxide (KOH).
• Weak acids and bases only partially dissociate in water, leaving some unreacted molecules behind.
- Examples of weak acids include acetic acid (CH3COOH) and formic acid (HCOOH).
- Examples of weak bases are ammonia (NH3) and methylamine (CH3NH2).