Question

Calculate the number of moles of NaOH that must be added to 1.0 L of 0.50 M HC₂H₃O₂ to produce a solution buffered at pH =4.00. Assume no volume change upon adding the NaOH. (Ka (HC₂H₃O₂) = 1.8 x 10⁻⁵)

Answer 1

To calculate the number of moles of NaOH required to produce a buffered solution at pH = 4.00, we use the Henderson-Hasselbalch equation. Given the pH of 4.00 and the pKa of HC2H3O2, we can solve for the ratio of [A-]/[HA]. Using the initial concentration of HC2H3O2 and the volume of the solution, we can calculate the number of moles of HC2H3O2.

Step-by-step explanation:

To calculate the number of moles of NaOH required to produce a solution buffered at pH = 4.00, we need to use the Henderson-Hasselbalch equation. The equation is: pH = pKa + log([A-]/[HA]), where pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the conjugate base (in this case, CH3COO-), and [HA] is the concentration of the acid (HC2H3O2).

Given that the pH is 4.00 and the pKa of HC2H3O2 is 1.8 x 10^-5, we can rearrange the equation to solve for [A-]/[HA]. Plugging in the values, we get: 4.00 = -log(1.8 x 10^-5) + log([A-]/[HA]). Solving this equation using logarithmic properties, we find that [A-]/[HA] = 10^(-4.00 + log(1.8 x 10^-5)).

Since we know the initial concentration of HC2H3O2 is 0.50 M and the volume of the solution is 1.0 L, we can calculate the moles of HC2H3O2 using the formula: moles = concentration x volume. Therefore, moles of HC2H3O2 = 0.50 M x 1.0 L = 0.50 mol.