pH of a buffer...?

Question

1) A buffer is prepared by dissolving 3.753g sodium acetate in 125.0mL of 0.1091M acetic acid. What is the pH of this buffer?

ALSO:

2) A 0.257g sample of solid acid is titrated with 40.05mL of 0.1121 M NaOH. This overshot the endpoint and 2.52ML of 0.0953 M HCl was used to back titrate. What is the equivalent mass of the acid?

Answer 1

Problem 1. Step 1. Find mol weight of NaOAc. Find the corresponding MOLES of NaOAc. Then multiply by 1/0.125 to get molarity of NaOAc.
For the reaction {HOAc} = [H+] + [OAc-], the Ka is given by [H+][OAc-]/[HOAc] = Ka.

In this buffer solution set-up, the OAc- ion is essentially that of the initial salt added, and the HOAc is essentially that of the initial acid. This fixes the [H+]. If this equilibrium is upset by some acid or base being added, the buffer reacts with the acid or base, converting the base to more [OAc-] or converting the acid to more [HOAc]. For SMALL additions of acid or base, this stabilizes the [H+]. So solve for [H+], since you know everything else in the Ka equation, and convert the result to pH.

#2. Find the moles of NaOH (about 4.5x10-3) and the moles of HCl ( about 2.5x10-4). The difference is the equivalent number of moles of acid in the solid. The rest is a bit tricky. Since we don't know exactly what the solid is, or if it absolutely pure whatever, we assume it is solid HCl, and take the equivalent number of moles from above and multiply it by 37, the mol weight of HCl. The number is NOT the sample weight.

Answer 2

go away it on my own, do no longer buffer, do a water replace with RODi water , or do no longer go away the lights fixtures on as lengthy. The longer the lights fixtures are on the better the PH will flow. Ph stability is a lot more advantageous major than the truly factor, so long because the point is between 7.8 to eight.4. under no circumstances attempt to buffer PH interior the tank, extremely verify and buffer alkalinity as mandatory.