Question

A buffer solution is made that is 0.417 M in and 0.417 M in . If for is , what is the pH of the buffer solution? pH = Write the net ionic equation for the reaction that occurs when 0.120 mol is added to 1.00 L of the buffer solution. (Use the lowest possible coefficients. Omit states of matter.)

Answer 1

Answer:

pH = 3.347

NO₂⁻ + H₃O⁺ → HNO₂

Explanation:

If the buffer is made with 0.417M of HNO₂ and 0.417M of NaNO₂ the pH of the solution is = pKa. A buffer which concentration of weak acid and conjugate base is the same has a pH = pKa

As Ka of the solution is 4.50x10⁻⁴, pKa is -log 4.50x10⁻⁴ = 3.347. Thus, pH = 3.347

The net ionic equation that occurs when 0.120 mol of HCl is added to 1.00L of the solution is:

NO₂⁻ + H₃O⁺ → HNO₂ + H₂O

The conjugate base (NaNO₂) reacts with strong acid (HCl, source of H₃O⁺) producing weak acid (HNO₂) and water. If a strong base is added, the weak acid reacts producing conjugate base and water.