Question

HC₂H₂O₂(aq) + H₂O(1) ≈ H₂O+ (aq) + C₂H₂O₂¯(ag) The chemical equation above represents the acid ionization equilibrium for HC₂H₂O₂ for which pK, -4.8. Which of the following is the best estimate for the pH of a buffer prepared by mixing 100. mL of 0.20 MHC₂H₂O₂ with 100. mL of 0.10 M NaC,H,O₂?​

Answer 1

Answer: 4.74

Step-by-step explanation:

First, we need to find the moles of each component in the buffer solution:

moles of HC2H3O2 = 0.20 mol/L x 0.100 L = 0.020 mol

moles of NaC2H3O2 = 0.10 mol/L x 0.100 L = 0.010 mol

Next, we can use the Henderson-Hasselbalch equation to find the pH of the buffer:

pH = pKa + log([C2H3O2-]/[HC2H3O2])

We know the pKa of HC2H3O2 is -4.8, and we can find the ratio of [C2H3O2-]/[HC2H3O2] using the moles and volumes of the components:

[C2H3O2-]/[HC2H3O2] = (moles of NaC2H3O2 / volume of solution containing HC2H3O2) / (moles of HC2H3O2 / volume of solution containing HC2H3O2)

= (0.010 mol / 0.200 L) / (0.020 mol / 0.200 L)

= 0.5

Plugging in these values to the Henderson-Hasselbalch equation, we get:

pH = -4.8 + log(0.5)

= 4.74

Therefore, the best estimate for the pH of the buffer is 4.74.