Question

What would happen if a buffer solution of ph 7.8 is added in comical flask that already had naoh solution and a plant twig with roots showing the respiration?

Answer 1

If 0.050 mol of HCl is added to 1.0 L of a buffer solution containing 0.125 M potassium acetate and 0.10 M acetic acid, what is the change in pH of the solution?

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We don’t even need the pKa to answer this question.

Using the Henderson-Hasselbalch equation, which is

pH = pKa + log(CBCA)

we can say that the initial pH is

pHi = pKa + log(0.1250.10)

Adding 0.050 mol of HCl will convert 0.050 mol of acetate (CB) to acetic acid (CA), so the final pH is

pHf = pKa + log(0.0750.15)

And then ΔpH = pHf - pHi, or

ΔpH = [pKa + log(0.0750.15)] - [pKa + log(0.1250.10)]

ΔpH = log(0.0750.15) - log(0.1250.10)

We can now go to calculator or simplify further by recognizing that log(B) - log(A) = log(BA):

ΔpH = log((0.075)(0.10)(0.15)(0.125))

And either way,

ΔpH = -0.40

Which, sanity check time, makes sense because adding acid will cause the pH to decrease.