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Calculate The Ph of A 0.00234 M Hbr Solution

Reviewed by Calculator Editorial Team

Calculating the pH of a hydrobromic acid (HBr) solution is essential in chemistry for understanding acid strength and solution properties. This guide provides a step-by-step method, the exact calculation formula, and practical interpretation of results.

How to Calculate the pH of a HBr Solution

The pH of a solution is a measure of its acidity or alkalinity. For a strong acid like HBr, the pH calculation is straightforward once you know the concentration of the acid. Here's the step-by-step process:

  1. Determine the molarity (M) of the HBr solution.
  2. Find the pH using the formula: pH = -log[H+].
  3. For strong acids like HBr, [H+] equals the concentration of the acid.
  4. Calculate the negative logarithm of the hydrogen ion concentration.

Key Point

HBr is a strong acid, so it completely dissociates in water, meaning [H+] equals the concentration of HBr.

The pH Calculation Formula

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

pH Formula for Strong Acids

pH = -log10[H+]

For HBr solutions: [H+] = [HBr]

Where:

  • pH is the measure of acidity
  • [H+] is the hydrogen ion concentration in moles per liter (M)
  • [HBr] is the concentration of hydrobromic acid in moles per liter (M)

Worked Example

Let's calculate the pH of a 0.00234 M HBr solution:

  1. Given: [HBr] = 0.00234 M
  2. Since HBr is a strong acid, [H+] = [HBr] = 0.00234 M
  3. Calculate pH: pH = -log(0.00234)
  4. Using a calculator: log(0.00234) ≈ 2.6306
  5. Therefore, pH = -2.6306 ≈ 2.63

Result

The pH of a 0.00234 M HBr solution is approximately 2.63.

Interpreting the Results

A pH of 2.63 indicates a moderately acidic solution. Here's what this means:

  • The solution is strongly acidic, as expected for HBr
  • It's less acidic than pure HBr (pH 0) but more acidic than common household acids
  • This concentration is typical for laboratory-grade HBr solutions

Practical Consideration

Always handle HBr solutions with care as they are corrosive and can cause skin and eye irritation.

Frequently Asked Questions

Why does HBr have a pH of 2.63 at 0.00234 M?
HBr is a strong acid that completely dissociates in water, so the hydrogen ion concentration equals the HBr concentration. The pH is then calculated from this concentration.
Can I use this formula for other strong acids?
Yes, this formula applies to any strong acid where the acid completely dissociates in water. Common examples include HCl, HNO3, and H2SO4.
What if the HBr concentration changes?
The pH will change proportionally. For example, doubling the concentration would decrease the pH by about 0.3 units (logarithmic relationship).
Is this calculation valid for weak acids?
No, this formula only applies to strong acids. Weak acids require a different approach considering their degree of dissociation.
How precise is this calculation?
The calculation is precise for the given concentration. For very dilute solutions, you might need to consider water autoionization.