Question

Classify the following aqueous solutions as strongly acidic, weakly acidic, neutral, weakly basic, or strongly basic: (a) battery acid, $\mathrm{pH}0$ (b) lime juice, $\mathrm{pH}2.7$ (c) distilled water, $\mathrm{pH}7.0$ (d) drain cleaner, $\mathrm{pH}13.5$

Short answer

(a) Strongly acidic, (b) Weakly acidic, (c) Neutral, (d) Strongly basic.

Step-by-step solution

Understanding pH Scale

The pH scale ranges from 0 to 14. A pH less than 7 indicates acidity, a pH equal to 7 is neutral, and a pH greater than 7 indicates basicity. The closer a pH is to 0, the stronger the acid, and conversely, the closer a pH is to 14, the stronger the base.

Classifying Battery Acid

Battery acid has a pH of 0. Since this is at the extreme low end of the pH scale, it is classified as strongly acidic.

Classifying Lime Juice

Lime juice has a pH of 2.7, which is lower than 7 but not at the extreme low end of the pH scale. Hence, it is classified as weakly acidic.

Classifying Distilled Water

Distilled water has a pH of 7.0, which is exactly neutral. Therefore, it is classified as neutral.

Classifying Drain Cleaner

Drain cleaner has a pH of 13.5, which is very high, indicating strong basicity. Thus, it is classified as strongly basic.

Key concepts

Acid-Base Classification

Understanding how to classify substances as acidic or basic is essential in chemistry.

• **Acidity and basicity** are determined by the pH scale, which ranges from 0 to 14.
• A **pH less than 7** signifies an acidic solution, while a **pH greater than 7** indicates a basic solution.
• A **pH of exactly 7** is neutral and typically corresponds to pure water.

Identifying whether a solution is acidic or basic helps us understand its chemical properties. For example, solutions with a low pH, like lemon juice or vinegar, are acidic because they contain more hydrogen ions. On the other hand, substances like baking soda or soaps, which have a higher pH, are basic due to a higher concentration of hydroxide ions. Properly classifying solutions allows us to predict their interactions with other substances and their potential impact on biological and environmental systems.

Strong Acids and Bases

Strong acids and bases are crucial in many chemical reactions due to their ability to completely disassociate in solution. **Strong Acids:** - These acids almost entirely dissociate into their ions in water, making them very effective at donating protons (H⁺ ions). - Common examples include **hydrochloric acid (HCl)** and **sulfuric acid (H₂SO₄)**. **Strong Bases:** - Similarly, strong bases dissociate completely, releasing hydroxide ions (OH⁻) into the solution. - **Sodium hydroxide (NaOH)** and **potassium hydroxide (KOH)** are typical examples. These substances are distinct due to their ability to rapidly change the pH level of a solution. This property makes them ideal for use in various industrial processes, from manufacturing to cleaning. However, it's also why handling them with care is crucial, as they can be corrosive and cause significant chemical burns.

Neutral Solutions

Neutral solutions are one of the simplest concepts to grasp in terms of acidity and alkalinity. - The **pH of a neutral solution** is exactly 7. - This is because there is a **balance of hydrogen ions (H⁺)** and **hydroxide ions (OH⁻)** in the solution. Pure distilled water is the best example of a neutral solution. When the concentration of hydrogen ions equals the concentration of hydroxide ions, the solution is neutral. Understanding neutrality is crucial in fields like medicine and biology, where maintaining homeostasis—an internal balance of pH—is vital for life. Moreover, neutral solutions serve as important reference points for scientists and educators when comparing and contrasting with more acidic or basic solutions.