Calculate Ph of 0.1000 M Ethylamine

Ethylamine (C₂H₅NH₂) is a weak base that dissociates in water to form ethylammonium ions and hydroxide ions. This calculator determines the pH of a 0.1000 M ethylamine solution using the Henderson-Hasselbalch equation.

Introduction

The pH of a solution is a measure of its acidity or basicity. For weak base solutions like ethylamine, we use the Henderson-Hasselbalch equation to calculate pH. Ethylamine is commonly used in organic synthesis and as a precursor to other compounds.

Key Point: Ethylamine is a weak base with a pK_a of approximately 10.75. This means it partially dissociates in water, affecting the solution's pH.

pH Calculation Formula

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

pH = pK_a + log₁₀([Base]/[Acid])

Where:

pK_a is the acid dissociation constant of the conjugate acid (10.75 for ethylammonium ion)
[Base] is the concentration of the weak base (ethylamine)
[Acid] is the concentration of the conjugate acid (ethylammonium ion)

For a solution of pure weak base, [Acid] = [Base] at equilibrium, so the equation simplifies to:

pH = pK_a + log₁₀(1) = pK_a

Calculation Example

Let's calculate the pH of a 0.1000 M ethylamine solution:

Identify the pK_a of ethylammonium ion: 10.75
Since it's a pure weak base solution, [Base] = [Acid] = 0.1000 M
Apply the simplified Henderson-Hasselbalch equation:

pH = 10.75 + log₁₀(1) = 10.75 + 0 = 10.75

The calculated pH of a 0.1000 M ethylamine solution is 10.75.

Interpreting Results

A pH of 10.75 indicates a strongly basic solution. This means:

The solution contains more hydroxide ions than hydronium ions
Ethylamine has dissociated significantly to form ethylammonium ions
The solution would turn blue litmus paper red

Practical Consideration: For more accurate results, consider temperature effects on pK_a and potential impurities in the solution.

Frequently Asked Questions

What is the pK_a of ethylammonium ion?: The pK_a of ethylammonium ion is approximately 10.75 at 25°C.
Why does the pH of a weak base solution equal its pK_a?: For a pure weak base solution, the concentration of the base equals the concentration of its conjugate acid at equilibrium, making the log term equal to zero.
How does temperature affect the pH calculation?: The pK_a of ethylammonium ion changes with temperature. At higher temperatures, the pK_a decreases, making the solution more basic.
Can this calculator be used for other weak bases?: Yes, the same principles apply to other weak bases. You would need to know the pK_a of the conjugate acid for accurate calculations.