Calculate The Ph of Each of The Following Aqueous Solutions

Calculating the pH of aqueous solutions is essential in chemistry, biology, and environmental science. This guide provides a step-by-step method to determine the pH of various solutions using the pH formula and practical examples.

Introduction to pH Calculation

The pH scale measures how acidic or basic a solution is. It ranges from 0 to 14, where:

pH 0-6 is acidic
pH 7 is neutral
pH 8-14 is basic

The pH is calculated using the concentration of hydrogen ions (H⁺) in a solution. The formula for pH is:

pH = -log[H⁺]

Where [H⁺] is the molar concentration of hydrogen ions in moles per liter (mol/L).

The pH Formula

The pH formula is derived from the definition of pH as the negative logarithm of the hydrogen ion concentration:

pH = -log₁₀[H⁺]

This formula allows chemists to determine the acidity or basicity of a solution based on the concentration of hydrogen ions. The pH scale is logarithmic, meaning each whole number change represents a tenfold difference in hydrogen ion concentration.

Note: The pH formula assumes the solution is at 25°C (298 K). Temperature affects the pH calculation, but this calculator uses the standard temperature.

Worked Examples

Let's calculate the pH of some common aqueous solutions using the pH formula.

Example 1: 0.1 M Hydrochloric Acid (HCl)

Given: [H⁺] = 0.1 M

pH = -log[0.1]

pH = -(-1) = 1

The pH of 0.1 M hydrochloric acid is 1, which is strongly acidic.

Example 2: 0.001 M Sodium Hydroxide (NaOH)

Given: [OH⁻] = 0.001 M

First, calculate [H⁺] using the relationship between [H⁺] and [OH⁻] in water:

[H⁺] × [OH⁻] = 1.0 × 10⁻¹⁴ M²

[H⁺] = (1.0 × 10⁻¹⁴) / [OH⁻]

[H⁺] = (1.0 × 10⁻¹⁴) / 0.001 = 1.0 × 10⁻¹¹ M

Now calculate the pH:

pH = -log[1.0 × 10⁻¹¹]

pH = -(-11) = 11

The pH of 0.001 M sodium hydroxide is 11, which is strongly basic.

Example 3: Pure Water

Given: [H⁺] = [OH⁻] = 1.0 × 10⁻⁷ M

pH = -log[1.0 × 10⁻⁷]

pH = -(-7) = 7

The pH of pure water is 7, which is neutral.

Frequently Asked Questions

What is the pH formula?: The pH formula is pH = -log[H⁺], where [H⁺] is the molar concentration of hydrogen ions.
How do I calculate the pH of a solution?: To calculate the pH, measure the concentration of hydrogen ions in the solution, then apply the pH formula.
What is the pH of pure water?: The pH of pure water is 7 at 25°C, which is considered neutral.
How does temperature affect pH calculations?: Temperature affects the pH calculation because the dissociation of water changes with temperature. This calculator assumes 25°C.
What is the pH range for acidic and basic solutions?: Solutions with a pH less than 7 are acidic, while those with a pH greater than 7 are basic. A pH of 7 is neutral.