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Calculate The Ph of A 0.50 M Solution of Nano2.

Reviewed by Calculator Editorial Team

This calculator helps you determine the pH of a 0.50 M solution of sodium nitrite (NaNO2). Sodium nitrite is a weak acid, and its pH can be calculated using standard acid dissociation constant (Ka) values.

How to Calculate the pH of NaNO2 Solution

The pH of a solution is a measure of its acidity or basicity. For weak acids like NaNO2, we calculate the pH using the following steps:

  1. Determine the concentration of the weak acid (NaNO2)
  2. Find the acid dissociation constant (Ka) for NaNO2
  3. Calculate the hydrogen ion concentration ([H+])
  4. Convert [H+] to pH using the formula pH = -log[H+]

Note: This calculation assumes the solution is dilute and that the activity coefficient is approximately 1.

The pH Calculation Formula

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

pH = -log10([H+])

Where [H+] is the hydrogen ion concentration

For weak acids, [H+] can be calculated using the following relationship:

[H+] = √(Ka × [HA])

Where:

  • Ka = Acid dissociation constant (for NaNO2, Ka ≈ 4.5 × 10-4)
  • [HA] = Concentration of the weak acid (0.50 M in this case)

Worked Example

Let's calculate the pH of a 0.50 M solution of NaNO2:

  1. Given: [NaNO2] = 0.50 M, Ka = 4.5 × 10-4
  2. Calculate [H+]: [H+] = √(4.5 × 10-4 × 0.50) ≈ √(2.25 × 10-4) ≈ 4.74 × 10-2 M
  3. Calculate pH: pH = -log(4.74 × 10-2) ≈ 1.32

Result

pH ≈ 1.32

A 0.50 M solution of NaNO2 has a pH of approximately 1.32, indicating it is a weak acid solution.

Interpreting the Results

The pH value of 1.32 indicates that the solution is acidic. Here's what this means:

  • The [H+] concentration is 4.74 × 10-2 M
  • The solution contains more hydrogen ions than hydroxide ions
  • This is characteristic of a weak acid solution

Remember: pH is a logarithmic scale, so small changes in pH represent large changes in [H+].

Frequently Asked Questions

What is the Ka value for NaNO2?

The acid dissociation constant (Ka) for NaNO2 is approximately 4.5 × 10-4 at 25°C.

Why is the pH of NaNO2 solution less than 7?

NaNO2 is a weak acid, so it partially dissociates in water, releasing H+ ions and resulting in a pH less than 7.

How does temperature affect the pH calculation?

The Ka value changes with temperature, so the pH calculation would need to use the appropriate Ka value for the specific temperature.