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Calculate The Ph for The Following Solutions and Indicate Whether

Reviewed by Calculator Editorial Team

The pH scale measures how acidic or basic a solution is. This calculator helps determine the pH of solutions and indicates whether they are acidic, basic, or neutral. Learn about the pH formula, scale, and practical applications.

What is pH?

The pH scale is a measure of how acidic or basic a solution is. It ranges from 0 to 14, with:

  • pH values less than 7 being acidic
  • pH 7 being neutral
  • pH values greater than 7 being basic (alkaline)

The pH scale is logarithmic, meaning each whole number change represents a tenfold difference in acidity or alkalinity. For example, a solution with pH 3 is ten times more acidic than one with pH 4.

pH Formula

The pH of a solution is calculated using the formula:

pH = -log10[H+]

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

For example, if a solution has a hydrogen ion concentration of 1 × 10-5 mol/L, its pH would be:

pH = -log10(1 × 10-5) = 5

How to Calculate pH

To calculate the pH of a solution:

  1. Determine the concentration of hydrogen ions [H+] in the solution in mol/L
  2. Take the negative logarithm (base 10) of the hydrogen ion concentration
  3. The result is the pH of the solution

For example, if a solution has [H+] = 1 × 10-8 mol/L:

pH = -log10(1 × 10-8) = 8

This solution would be basic with a pH of 8.

pH Scale

The pH scale ranges from 0 to 14:

  • 0-6: Acidic solutions (e.g., lemon juice, vinegar)
  • 7: Neutral solutions (e.g., pure water)
  • 8-14: Basic (alkaline) solutions (e.g., baking soda, soap)

Each whole number on the pH scale represents a tenfold difference in acidity or alkalinity. For example, a pH 4 solution is ten times more acidic than a pH 5 solution.

Note: The pH scale is logarithmic, so small changes in pH can represent significant differences in acidity or alkalinity.

Examples

Example 1: Vinegar

Vinegar typically has a pH of around 2.5. Using the pH formula:

pH = -log10([H+])

If pH = 2.5, then [H+] = 10-2.5 ≈ 3.16 × 10-3 mol/L

This confirms vinegar is acidic with a pH of 2.5.

Example 2: Baking Soda Solution

A saturated baking soda solution typically has a pH of around 8.4. Using the pH formula:

pH = -log10([H+])

If pH = 8.4, then [H+] = 10-8.4 ≈ 3.98 × 10-9 mol/L

This confirms the solution is basic with a pH of 8.4.

FAQ

What is the pH of pure water?

Pure water has a pH of 7, which is considered neutral.

How does temperature affect pH measurements?

Temperature can affect pH measurements because the ionization of water changes with temperature. Most pH measurements are standardized to 25°C (77°F).

What is the difference between pH and pOH?

pH measures acidity, while pOH measures alkalinity. They are related by the equation: pH + pOH = 14 at 25°C.