Question

What amount of hcl gas must be added to 2.00 l of a buffer solution that contains [aceticacid]=2.0moll−1 and [acetate]=1.0moll−1 in order to produce a solution with ph=4.35 ? ( ka(ch3cooh)=1.8×10−5 )?

Answer 1

To find the amount of HCl gas required to create a buffer solution with a pH of 4.35, use the Henderson-Hasselbalch equation accounting for the reaction of HCl with the buffer components.

Step-by-step explanation:

To determine the amount of HCl gas needed to be added to a buffer solution to achieve a pH of 4.35, the Henderson-Hasselbalch equation is used:
pH = pKa + log([A-]/[HA])

Given [Acetic acid] = 2.0 mol L-1 and [Acetate] = 1.0 mol L-1, and the Ka for acetic acid is 1.8 × 10-5, we first calculate pKa:

pKa = -log(Ka) = -log(1.8 × 10-5)

Using the Henderson-Hasselbalch equation:

4.35 = pKa + log(1.0/2.0)

To find the new acetate concentration post HCl addition, you would solve for the concentration of acetate that satisfies the pH requirement. This is effectively determining the change in buffer component concentrations due to the added HCl, which will neutralize some of the acetate ions, forming more acetic acid.

We assume the volume of the buffer solution remains at 2.00 L. The mass of HCl gas can be calculated from the number of moles needed and the molar mass of HCl.