Calculate Oh Poh and Ph for Each of The Following

Introduction

The pH scale is a measure of the acidity or basicity of an aqueous solution. It's defined as the negative logarithm (base 10) of the hydrogen ion concentration (H⁺). The pOH is similarly defined as the negative logarithm of the hydroxide ion concentration (OH⁻).

In pure water at 25°C, the concentrations of H⁺ and OH⁻ are equal (1 × 10⁻⁷ M), resulting in a pH of 7.00 and pOH of 7.00. For any aqueous solution, the sum of pH and pOH is always 14:

This relationship is fundamental to understanding solution acidity and basicity. Solutions with a pH less than 7 are acidic, while those with a pH greater than 7 are basic. The pH scale ranges from 0 to 14.

Formulas

The key formulas for calculating pH, pOH, and OH⁻ are:

These formulas are essential for determining the acidity or basicity of solutions in various chemical and biological contexts.

Examples

Let's look at some examples to illustrate how these calculations work:

Example 1: Pure Water

In pure water at 25°C:

• [H⁺] = 1 × 10⁻⁷ M
• pH = -log(1 × 10⁻⁷) = 7.00
• [OH⁻] = 1 × 10⁻⁷ M
• pOH = -log(1 × 10⁻⁷) = 7.00

Example 2: Acidic Solution

For a solution with [H⁺] = 1 × 10⁻³ M:

• pH = -log(1 × 10⁻³) = 3.00
• [OH⁻] = 1 × 10^(-(14 - 3.00)) = 1 × 10⁻¹¹ M
• pOH = -log(1 × 10⁻¹¹) = 11.00

Example 3: Basic Solution

For a solution with pOH = 5.00:

• [OH⁻] = 10^(-5.00) = 1 × 10⁻⁵ M
• pH = 14 - 5.00 = 9.00
• [H⁺] = 10^(-9.00) = 1 × 10⁻⁹ M

These examples demonstrate how to calculate pH, pOH, and OH⁻ for different types of solutions.