Question

the weak acid ch3cooh has a pka of 4.76. a solution is prepared by mixing 500.ml of 0.150mch3cooh(aq) and 0.0200mol of naoh(s) . which of the following can be used to calculate the ph of the solution?

Answer 1

1. Determine the limiting reactant: compare moles of CH₃COOH to moles of NaOH (0.0200 mol).

2. Calculate excess moles of the remaining reactant and determine moles of CH₃COONa formed.

3. Use Henderson-Hasselbalch equation with pKa (4.76) to find the pH of the resulting solution.

Step-by-step explanation:

To calculate the pH of the solution, start by determining the moles of acetic acid (CH₃COOH) in the 500 mL of 0.150 M solution. This is found by multiplying the molarity (0.150 mol/L) by the volume in liters (0.500 L), resulting in the moles of CH₃COOH present. Simultaneously, 0.0200 mol of sodium hydroxide (NaOH) is added. The limiting reactant is identified by comparing the moles of CH₃COOH to the moles of NaOH.

The reactant with fewer moles is the limiting one.Once the limiting reactant is determined, calculate the excess moles of the other reactant. The balanced chemical equation (CH₃COOH + NaOH → CH₃COONa + H₂O) indicates a 1:1 ratio, allowing the conversion of excess moles to moles of the formed salt (CH₃COONa).

Finally, employ the Henderson-Hasselbalch equation, utilizing the pKa of acetic acid (4.76) and the ratio of CH₃COO⁻ to CH₃COOH, to find the pH of the resulting solution. This equation is pH = pKa + log([CH₃COO⁻]/[CH₃COOH]). The calculated pH provides insight into the acidic or basic nature of the solution resulting from the neutralization reaction.

Answer 2

To calculate the pH after the addition of NaOH to acetic acid, we use the stoichiometry of the neutralization reaction and the Henderson-Hasselbalch equation, taking into account the pKa of acetic acid (4.76) and the concentrations of acid and conjugate base formed.

Step-by-step explanation:

To calculate the pH of the solution after mixing 500 mL of 0.150 M CH3COOH with 0.0200 mol of NaOH, we must understand that NaOH is a strong base that will completely neutralize an equivalent amount of the weak acid CH3COOH to form water and the acetate ion (CH3COO-). The reaction is:

CH3COOH (aq) + OH- (aq) → CH3COO- (aq) + H2O (l)

Here are the steps to calculate the pH:

Calculate the number of moles of NaOH added to the solution, which is already provided (0.0200 moles).

Calculate the initial moles of CH3COOH before the reaction by multiplying the concentration by the volume (in liters).

Calculate the moles of CH3COOH that remain by subtracting the moles of NaOH from the initial moles of CH3COOH.

Calculate the moles of CH3COO- produced, which will be equal to the moles of NaOH added, assuming complete neutralization.

Calculate the new concentrations of CH3COOH and CH3COO- in the final solution.

Using the Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), calculate the pH of the buffer solution created.

The pKa of acetic acid is given as 4.76, which is crucial in the Henderson-Hasselbalch equation to find the pH.