6 Calculate The Ph of 0.100 M Kbro Solution K

This calculator helps you determine the pH of a 0.100 M potassium bromide (KBr) solution. The pH of a solution is a measure of its acidity or basicity, and it's calculated using the concentration of hydrogen ions in the solution.

Introduction

The pH of a solution is a crucial parameter in chemistry, particularly in the study of acids and bases. For a 0.100 M KBr solution, we can calculate its pH using the properties of the potassium bromide salt and the concept of ionization.

Potassium bromide (KBr) is a salt that dissociates completely in water, forming potassium ions (K⁺) and bromide ions (Br⁻). The bromide ion itself is a weak conjugate base, but its contribution to the pH is negligible compared to the potassium ion, which does not affect the pH.

Formula

The pH of a solution can be calculated using the following formula:

pH = -log₁₀[H⁺]

Where [H⁺] is the concentration of hydrogen ions in the solution, measured in moles per liter (M).

For a solution of a strong electrolyte like KBr, the concentration of hydrogen ions is determined by the autoionization of water:

H₂O ⇌ H⁺ + OH⁻

Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25°C

Since the concentration of hydroxide ions (OH⁻) is equal to the concentration of hydrogen ions (H⁺) in pure water, we can use this to find the pH of the solution.

Calculation

To calculate the pH of a 0.100 M KBr solution, we follow these steps:

Determine the concentration of hydrogen ions ([H⁺]) using the autoionization constant of water (Kw).
Calculate the pH using the formula pH = -log₁₀[H⁺].

Given that Kw = 1.0 × 10⁻¹⁴ at 25°C, we can find [H⁺] as follows:

[H⁺] = √Kw = √(1.0 × 10⁻¹⁴) = 1.0 × 10⁻⁷ M

Using this value, we can calculate the pH:

pH = -log₁₀(1.0 × 10⁻⁷) = 7.0

This calculation shows that a 0.100 M KBr solution has a pH of 7.0, which is neutral.

Interpretation

The pH of 7.0 indicates that the solution is neutral. This means that the concentration of hydrogen ions (H⁺) is equal to the concentration of hydroxide ions (OH⁻), which is characteristic of pure water.

For a 0.100 M KBr solution, the addition of the salt does not significantly change the pH because:

KBr is a strong electrolyte that dissociates completely into K⁺ and Br⁻ ions.
The bromide ion (Br⁻) is a weak conjugate base and does not significantly affect the pH.
The potassium ion (K⁺) does not react with water to affect the pH.

Therefore, the pH of the solution remains close to that of pure water, which is 7.0.

FAQ

Why is the pH of a 0.100 M KBr solution 7.0?

The pH of 7.0 is characteristic of pure water. In a 0.100 M KBr solution, the salt dissociates completely into K⁺ and Br⁻ ions, and neither ion significantly affects the pH. The pH remains close to that of pure water due to the autoionization of water.

Does the concentration of KBr affect the pH?

No, the concentration of KBr does not significantly affect the pH. Even at high concentrations, the pH of a KBr solution remains close to 7.0 because the salt dissociates completely and neither ion reacts with water to affect the pH.

What is the significance of the pH of a solution?

The pH of a solution is significant because it indicates the acidity or basicity of the solution. A pH of 7.0 is neutral, while values below 7.0 indicate acidity and values above 7.0 indicate basicity. The pH is crucial in various chemical and biological processes.