Assume that you are given a solution of an unknown acid or base. How can you tell whether the unknown substance is acidic or basic?

Verified step by step guidance

1. insert step 1> Determine the pH of the solution using a pH meter or pH paper.
2. insert step 2> Compare the pH value to the neutral pH of 7.
3. insert step 3> If the pH is less than 7, the solution is acidic.
4. insert step 4> If the pH is greater than 7, the solution is basic.
5. insert step 5> If the pH is exactly 7, the solution is neutral, indicating neither acidic nor basic properties.

Key Concepts

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH less than 7 indicates an acidic solution, while a pH greater than 7 indicates a basic solution. A pH of exactly 7 is considered neutral, typical of pure water. Understanding the pH scale is essential for determining the nature of the unknown substance.

Indicators

Indicators are substances that change color in response to the pH of a solution, providing a visual means to determine whether a solution is acidic or basic. Common indicators include litmus paper, which turns red in acidic solutions and blue in basic ones, and phenolphthalein, which is colorless in acidic solutions and pink in basic ones. Using indicators is a practical method for identifying the nature of the unknown substance.

Acid-Base Theory

Acid-base theory encompasses various definitions, including the Arrhenius, Brønsted-Lowry, and Lewis theories, which describe acids as proton donors and bases as proton acceptors. Understanding these theories helps in predicting the behavior of the unknown substance in reactions and its interaction with water. This theoretical framework is crucial for classifying the unknown substance as either an acid or a base.