Protonated Percentage Calculator Online

The protonated percentage calculator is a valuable tool used in chemistry to assess the extent of protonation of a weak base in a solution. It utilizes the Henderson-Hasselbalch equation, which can be expressed as:

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

Let’s break down this equation:

• pH: This represents the acidity or proton concentration of the solution.
• pKa: The negative logarithm (base 10) of the acid dissociation constant (Ka) of the weak acid.
• [A-]: The concentration of the conjugate base (e.g., methylammonium, CH₃NH₃⁺).
• [HA]: The concentration of the weak base (e.g., methylamine, CH₃NH₂).

Example of Protonated Percentage Calculator

To illustrate the practical use of the protonated percentage calculator, let’s consider a scenario:

Suppose we have a solution of methylamine (CH₃NH₂) with a concentration of 0.1 M (moles per liter) at 25°C. We want to calculate the percentage of methylamine that is protonated at a specific pH.

First, we need the pKa value for the methylamine/methylammonium pair at 25°C, which is approximately 10.6.

Let’s assume we want to know the percent protonation at pH 9.0. We can use the Henderson-Hasselbalch equation to calculate it:

pH = pKa + log([A-]/[CH₃NH₂])

9.0 = 10.6 + log([A-]/[CH₃NH₂])

Now, rearrange the equation to solve for [A-]/[CH₃NH₂]:

log([A-]/[CH₃NH₂]) = 9.0 – 10.6

log([A-]/[CH₃NH₂]) = -1.6

[A-]/[CH₃NH₂] = 10^(-1.6) ≈ 0.0251

Now, to calculate the percent protonation:

Percent protonated = [A-]/[CH₃NH₂] * 100%

Percent protonated = 0.0251 * 100% ≈ 2.51%

So, at pH 9.0, approximately 2.51% of the methylamine in the solution is protonated to form methylammonium ions (CH₃NH₃⁺), while the rest remains unprotonated methylamine (CH₃NH₂).

General Terms for Quick Reference

Here are some general terms that may be helpful for users when using the protonated percentage calculator or dealing with similar calculations:

• pH: The measure of acidity or alkalinity of a solution.
• pKa: The acid dissociation constant for a weak acid.
• Concentration: The amount of a substance (usually in moles) per unit volume (usually in liters) of a solution.
• Percentage: A ratio expressed as a fraction of 100.

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