A solution turns red litmus blue, its \(\mathrm{pH}\) is likely to be (a) 1 (b) 4 (c) 5 (d) 10

Understanding how solutions are classified as acidic or basic is crucial. The \(\text{pH}\) scale, ranging from 0 to 14, is used to determine this.

• Solutions with a \(\text{pH}\) less than 7 are considered acidic.
• Solutions with a \(\text{pH}\) of 7 are neutral.
• Solutions with a \(\text{pH}\) greater than 7 are considered basic.

The \(\text{pH}\) value is a measurement of the hydrogen ion concentration in a solution. Acidic solutions have a high concentration of hydrogen ions (H⁺), while basic solutions have a low concentration of hydrogen ions but a higher concentration of hydroxide ions (OH⁻). For instance, lemon juice, with a \(\text{pH}\) around 2, is highly acidic. Conversely, household ammonia, with a \(\text{pH}\) around 11, is basic.

Understanding these concepts helps in interpreting experiments and chemical reactions involving different solutions.

The litmus test is a simple and convenient method to determine whether a solution is acidic or basic.

• Red litmus paper turns blue in a basic solution.
• Blue litmus paper turns red in an acidic solution.

Litmus paper is infused with dyes which react to the hydrogen or hydroxide ions present in the solution. When conducting a litmus test, observing the color change provides clear evidence of the solution's nature. For example, if red litmus paper turns blue, the solution has a \(\text{pH}\) greater than 7, indicating it is basic. Conversely, if blue litmus paper turns red, it signifies that the solution has a \(\text{pH}\) less than 7, which means it is acidic.

The litmus test is widely used in educational labs as well as in industrial applications to quickly assess the \(\text{pH}\) of various substances.

Basic solutions, also known as alkaline solutions, have some distinct properties and uses.

Key characteristics of basic solutions include:

• Slippery feel
• Bitter taste
• Ability to conduct electricity

An everyday example is soapy water. Bases are used in various cleaning products due to their ability to neutralize acids and break down organic materials. One way to produce a basic solution is by dissolving a base, such as sodium hydroxide (NaOH), in water.

The \(\text{pH}\) of a basic solution typically ranges from just above 7 up to 14. For example, a solution with a \(\text{pH}\) of 10, like many antacid tablets, neutralizes stomach acid and provides relief from heartburn. Therefore, understanding basic solutions is useful not only in scientific contexts but also in everyday life, from cooking to cleaning.