Question

(a) Name three common weak acids. (b) Name one common weak base. (c) What is the major difference between a weak acid and a strong acid or between a weak base and a strong base, and what experiment would you perform to observe it?

Short answer

Common weak acids: acetic acid, citric acid, carbonic acid. Common weak base: ammonia. Difference: extent of dissociation. Experiment: conduct a conductivity test.

Step-by-step solution

Identify Common Weak Acids

Weak acids only partially dissociate in water. Three common weak acids are acetic acid (CH₃COOH), citric acid (C₆H₈O₇), and carbonic acid (H₂CO₃).

Identify a Common Weak Base

Weak bases only partially dissociate in water. One common weak base is ammonia (NH₃).

Major Difference Between Weak vs. Strong Acids/Bases

The major difference is the extent of dissociation in water. Strong acids/bases completely dissociate, while weak acids/bases partially dissociate. For example, hydrochloric acid (HCl) is a strong acid, and sodium hydroxide (NaOH) is a strong base.

Experiment to Observe the Difference

Perform a conductivity test. Measure the electrical conductivity of solutions prepared with equal molar concentrations of a strong acid/base and a weak acid/base. Strong acids/bases will show higher conductivity due to complete dissociation, whereas weak acids/bases will show lower conductivity due to partial dissociation.

Key concepts

weak acid examples

Weak acids are acids that do not dissociate completely in water. Instead, only a small portion of the acid molecules ionize.
This partial dissociation means they release fewer hydrogen ions (H⁺) compared to strong acids.
Here are three common examples of weak acids that you might see:

• **Acetic acid (CH₃COOH)**: Commonly found in vinegar. It gives vinegar its characteristic sour taste.
• **Citric acid (C₆H₈O₇)**: Present in citrus fruits like lemons and oranges. Often used as a natural preservative and to add a sour flavor in foods and drinks.
• **Carbonic acid (H₂CO₃)**: Formed when carbon dioxide (CO₂) is dissolved in water. It is present in carbonated beverages like soda.

Understanding weak acids helps in recognizing everyday substances we encounter.

weak base examples

Just like weak acids, weak bases do not fully dissociate in water. This results in a lower concentration of hydroxide ions (OH⁻).
Instead, only a small number of base molecules ionize or react with water.
A common weak base example is:

• **Ammonia (NH₃)**: Often used as a household cleaner. It has a distinctive pungent smell and is less corrosive than strong bases.

Understanding weak bases can help you grasp why some basic solutions are safer and less reactive than others.

dissociation in water

Dissociation in water is the process where acids and bases separate into ions when dissolved.
This process defines the strength of the acid or base.

• **Strong acids/bases**: Completely dissociate in water, meaning they break apart fully into ions. For example, hydrochloric acid (HCl) dissociates into H⁺ and Cl⁻, and sodium hydroxide (NaOH) dissociates into Na⁺ and OH⁻.
• **Weak acids/bases**: Only partially dissociate in water, meaning only some of the molecules break into ions while the rest stay intact. For instance, acetic acid (CH₃COOH) dissociates slightly to form H⁺ and CH₃COO⁻ ions.

The extent of dissociation affects many properties of the solution, such as pH and conductivity.

strong vs. weak acids and bases

The major difference between strong and weak acids and bases lies in their dissociation in water:

• **Strong acids/bases:** These substances fully dissociate yielding a high concentration of ions. This complete dissociation makes them more reactive and more capable of conducting electricity.
• **Weak acids/bases:** These only partially dissociate, resulting in fewer ions in solution. This partial dissociation means they are less reactive and less conductive compared to strong acids/bases.

The reactivity and conductivity of these acids and bases can be experimentally measured and observed.

conductivity test

Conductivity is a measure of a solution's ability to conduct electricity, which depends on the concentration of ions present.
It can be used to distinguish between strong and weak acids/bases:

• **Experimental setup**: Prepare solutions of equal molar concentration for both a strong acid/base and a weak acid/base. Then, measure their electrical conductivity using a conductivity meter.
• **Observations**: The strong acid/base solution will have higher conductivity due to a higher concentration of dissociated ions. Conversely, the weak acid/base solution will display lower conductivity because of fewer dissociated ions.

This experiment helps in understanding the practical implications of dissociation in different acidic and basic solutions.