Problem 10 - Chemistry and Chemical Reactivity

Question

Name and give the formulas of two acids that are strong electrolytes and one acid that is a weak electrolyte. Name and give formulas of two bases that are strong electrolytes and one base that is a weak electrolyte.

Step-by-Step Solution

Answer

Strong acids: HCl, H2SO4; Weak acid: CH3COOH. Strong bases: NaOH, KOH; Weak base: NH3.

Step 1: Understanding Electrolytes

Electrolytes are substances that can dissociate into ions in solution, allowing the solution to conduct electricity. Strong electrolytes completely dissociate, while weak electrolytes only partially dissociate.

Step 2: Identifying Strong Acids

Strong acids are acids that fully dissociate into their ions in water. Two common strong acids are hydrochloric acid, with the formula \( \text{HCl} \), and sulfuric acid, with the formula \( \text{H}_2\text{SO}_4 \).

Step 3: Identifying a Weak Acid

A weak acid only partially dissociates in solution. Acetic acid, with the formula \( \text{CH}_3\text{COOH} \), is a common example of a weak acid.

Step 4: Identifying Strong Bases

Strong bases completely dissociate into hydroxide ions in solution. Sodium hydroxide (\( \text{NaOH} \)) and potassium hydroxide (\( \text{KOH} \)) are two examples of strong bases.

Step 5: Identifying a Weak Base

A weak base does not fully dissociate in solution. Ammonia, with the formula \( \text{NH}_3 \), is a typical weak base, as it partially dissociates to form ammonium ions \( \text{NH}_4^+ \).

Key Concepts

Strong Acids

Strong acids are substances that completely dissociate into their ions when they dissolve in water. This means that every molecule of acid separates into positively charged hydrogen ions (H⁺) and negatively charged ions.

• Hydrochloric Acid (HCl): When dissolved in water, it breaks apart completely into H⁺ and Cl⁻ ions. This reaction allows it to conduct electricity efficiently by creating a large number of ions.
• Sulfuric Acid (H₂SO₄): This acid also dissociates fully, releasing two H⁺ ions and SO₄²⁻ ions, increasing the number of ions in the solution, thus increasing conductivity.

The full dissociation of strong acids makes them powerful electrolytes, contributing significantly to the conductivity of solutions. Remember, more ions in a solution typically mean better conductivity.

Weak Acids

Weak acids only partially dissociate in water. This means that only a fraction of the acid molecules break down into ions, while the rest remain intact. This incomplete dissociation leads to fewer ions in the solution.

• Acetic Acid (CH₃COOH): A well-known weak acid found in vinegar, it partially dissociates to form H⁺ and CH₃COO⁻ ions. Because not all molecules dissociate, the solution remains a poor conductor of electricity compared to strong acids.

The presence of fewer ions is why weak acids are weaker electrolytes than strong acids. The incomplete ionization characterizes them and plays a crucial role in buffering solutions.

Strong Bases

Strong bases, much like strong acids, dissociate completely in water. They release hydroxide ions (OH⁻) and have a high degree of ionic dissociation, which makes them effective conductors of electricity.

• Sodium Hydroxide (NaOH): This base dissociates entirely into Na⁺ and OH⁻ ions in solution, contributing to its strength as an electrolyte.
• Potassium Hydroxide (KOH): KOH works similarly to NaOH, breaking down into K⁺ and OH⁻ ions, also enhancing its electrical conductivity by providing a higher concentration of ions.

The strong bases provide solutions with high conductivity and high pH levels due to the presence of free hydroxide ions.

Weak Bases

Unlike strong bases, weak bases do not completely dissociate into ions. This partial dissociation results in fewer available ions to conduct electricity in solution.

• Ammonia (NH₃): In water, ammonia reacts to form ammonium ions (NH₄⁺) and hydroxide ions (OH⁻), but this reaction does not proceed fully. Most ammonia stays in its molecular form, making it a weak base.

The low degree of ionization in weak bases is due to equilibrium between the base and the ions it forms. This equilibrium makes weak bases less effective electrolytes compared to strong bases, offering less conductive solutions.