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Calculate The Ph of A 0.50 M Solution of Nano2.

Reviewed by Calculator Editorial Team

How to Calculate the pH of a NaNO2 Solution

The pH of a sodium nitrite (NaNO2) solution can be calculated using standard acid-base chemistry principles. Sodium nitrite is a weak acid, so its pH depends on the concentration of the solution.

To calculate the pH, we use the Henderson-Hasselbalch equation, which relates the pH of a buffer solution to the ratio of the concentrations of a weak acid and its conjugate base.

Key Concepts

  • NaNO2 dissociates in water to form HNO2 and OH-
  • The equilibrium constant (Ka) for HNO2 is known
  • The pH is calculated from the hydrogen ion concentration

The pH Formula for NaNO2 Solutions

The pH of a NaNO2 solution is calculated using the following steps:

Step 1: Dissociation of NaNO2

NaNO2 + H2O ⇌ HNO2 + OH-

Step 2: pH Calculation

pH = pKa + log([HNO2]/[NaNO2])

Where pKa is the negative logarithm of the acid dissociation constant for HNO2

The pKa value for HNO2 is approximately 3.15 at 25°C.

Worked Example: 0.50 M NaNO2 Solution

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

  1. Given: [NaNO2] = 0.50 M, pKa = 3.15
  2. Since NaNO2 is a weak acid, [HNO2] ≈ [NaNO2] = 0.50 M
  3. Plug into the equation: pH = 3.15 + log(0.50/0.50) = 3.15 + log(1) = 3.15 + 0 = 3.15

Result

The calculated pH of a 0.50 M NaNO2 solution is 3.15.

Interpreting the pH Result

A pH of 3.15 indicates a moderately acidic solution. This is typical for weak acid solutions like NaNO2.

Key points to consider:

  • The solution is acidic but not strongly so
  • It's not corrosive to most materials
  • Neutralization would be required for many applications
Comparison of pH Values
pH Range Character Example Solutions
0-3 Strongly acidic Battery acid, stomach acid
3-7 Moderately acidic Vinegar, citrus juices
7 Neutral Pure water

Frequently Asked Questions

What is the pH of a 0.50 M NaNO2 solution?

The pH of a 0.50 M NaNO2 solution is approximately 3.15.

How does concentration affect the pH of NaNO2 solutions?

For weak acids like NaNO2, the pH changes logarithmically with concentration. Higher concentrations result in lower pH values.

Is NaNO2 solution safe to handle?

NaNO2 solutions are generally safe to handle, but proper safety precautions should be taken when working with any chemical solution.

Can I use this calculator for other weak acids?

This calculator is specifically designed for NaNO2 solutions. For other weak acids, you would need to use the appropriate pKa value.