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Calculate Ph of 0.1 M Hoac

Reviewed by Calculator Editorial Team

This calculator helps you determine the pH of a 0.1 M HOAC (hydroxyacetic acid) solution. HOAC is a weak acid commonly used in chemical and biological applications. Understanding its pH is essential for proper handling and reaction conditions.

Introduction

Hydroxyacetic acid (HOAC) is a weak organic acid with the chemical formula CH2OHCOOH. It's commonly used in chemical synthesis, as a preservative, and in biological research. The pH of a HOAC solution depends on its concentration and the dissociation constant of the acid.

This guide explains how to calculate the pH of a 0.1 M HOAC solution, including the formula, assumptions, and interpretation of results.

How to Use This Calculator

Using our pH calculator for HOAC solutions is straightforward:

  1. Enter the concentration of HOAC in molarity (M). For this page, the concentration is fixed at 0.1 M.
  2. Click the "Calculate" button to compute the pH.
  3. Review the result and interpretation section.
  4. Use the "Reset" button to clear the calculator for new calculations.

The calculator uses the dissociation constant (Ka) of HOAC to determine the pH. The default Ka value is 1.8 × 10-4, which is typical for HOAC at 25°C.

Formula and Assumptions

pH Calculation Formula

The pH of a weak acid solution can be calculated using the Henderson-Hasselbalch equation:

pH = pKa + log10([A-]/[HA])

Where:

  • pKa = -log10(Ka)
  • [A-] = concentration of conjugate base
  • [HA] = concentration of weak acid

Assumptions

  • The solution is dilute (concentration ≤ 0.1 M).
  • The temperature is 25°C.
  • The dissociation constant (Ka) of HOAC is 1.8 × 10-4.
  • Water autoionization is negligible at this concentration.

Worked Example

Let's calculate the pH of a 0.1 M HOAC solution step by step:

  1. Given: [HA] = 0.1 M, Ka = 1.8 × 10-4
  2. Calculate pKa: pKa = -log10(1.8 × 10-4) ≈ 3.74
  3. At equilibrium, [A-] ≈ √(Ka × [HA]) ≈ √(1.8 × 10-4 × 0.1) ≈ 0.0134 M
  4. Apply Henderson-Hasselbalch: pH = 3.74 + log10(0.0134/0.1) ≈ 3.74 - 0.88 ≈ 2.86

The calculated pH is approximately 2.86, which matches the calculator result.

Interpreting Results

A pH of 2.86 indicates a strongly acidic solution. This is expected for HOAC at 0.1 M concentration. The solution will:

  • Turn red litmus paper blue.
  • React with strong bases to form a salt and water.
  • Have limited buffering capacity at this concentration.

For more concentrated solutions, the pH will decrease further. For more dilute solutions, the pH will approach the pKa value of 3.74.

Frequently Asked Questions

What is the pH of a 0.1 M HOAC solution?
The pH is approximately 2.86, calculated using the Henderson-Hasselbalch equation with the dissociation constant of HOAC.
How does concentration affect the pH of HOAC?
Higher concentrations of HOAC will result in lower pH values, while more dilute solutions will have pH values closer to the pKa of HOAC (3.74).
Is HOAC a strong or weak acid?
HOAC is a weak acid with a dissociation constant (Ka) of 1.8 × 10-4, indicating it doesn't fully dissociate in water.
Can I use this calculator for other weak acids?
This calculator is specifically designed for HOAC solutions. For other weak acids, you would need to adjust the dissociation constant accordingly.