How to balance an equation

Question

A buffer is preparing a solution by using 30 mL of 0.15 M NaF, with 30 mL of 0.2 M HF. Ka of HF is 6.6 x 10^-4

a.) A small amount of 3 M H₂SO₄ is added to the buffers solution and the pH becomes slightly more acidic. Write a balanced equation to show how the buffer solution resisted a significant amount of change in pH when H₂SO₄ was added.

Answer 1

In this buffer, you have a weak acid, HF and the conjugate base, NaF.

When acid (H+) is added, it will react with the conjugate base, F-, to produce more of the weak acid, HF.

F^- + H⁺ ==> HF and because HF is weak, it doesn't ionize too much and so the added H+ is essentially removed from solution and pH doesn't change by a lot.

Looking at the complete molecular equation, we would have...

2NaF + H₂SO4 ==> 2HF + Na₂SO₄ Again, note that after adding H2SO4, we have formed a WEAK acid, HF and so the pH doesn't change significantly.