An ________ solution has a concentration of hydrogen ions more than that of pure water. A ________ solution has a low concentration of hydrogen ions, fewer than that of pure water. *
The Correct Answer and Explanation is:
The correct answers to the blanks are:
- Acidic solution
- Basic (or alkaline) solution
Explanation:
The concentration of hydrogen ions (H⁺) in a solution determines whether it is acidic, neutral, or basic. Pure water, at 25°C, has a neutral pH of 7. This means it has an equal concentration of hydrogen ions (H⁺) and hydroxide ions (OH⁻), each being 1 × 10⁻⁷ M. When the concentration of H⁺ ions in a solution increases above this value, the solution becomes acidic, and when it decreases, the solution becomes basic (alkaline).
- Acidic Solutions:
An acidic solution has a higher concentration of hydrogen ions (H⁺) compared to pure water. Acids are substances that release hydrogen ions when dissolved in water. The pH scale, which ranges from 0 to 14, measures the acidity or alkalinity of a solution. A pH value less than 7 indicates an acidic solution. As the concentration of H⁺ ions increases, the pH decreases. For example, hydrochloric acid (HCl) dissociates in water to release H⁺ ions, thus lowering the pH and making the solution acidic.
- Example: Lemon juice and stomach acid have a pH around 2–3, indicating high H⁺ concentrations.
- Basic (Alkaline) Solutions:
A basic or alkaline solution has a lower concentration of hydrogen ions than pure water, meaning it has a higher concentration of hydroxide ions (OH⁻). Bases are substances that can accept hydrogen ions or donate hydroxide ions. A basic solution has a pH greater than 7. As the concentration of OH⁻ ions increases, the concentration of H⁺ ions decreases, making the solution less acidic.
- Example: Solutions like sodium hydroxide (NaOH) are basic. When NaOH dissolves in water, it dissociates into Na⁺ and OH⁻ ions, increasing the OH⁻ concentration and raising the pH.
In summary, an acidic solution has a concentration of hydrogen ions greater than pure water, while a basic solution has a lower concentration of hydrogen ions. These variations in ion concentrations determine the pH and influence the chemical properties of the solution.