What mass of sodium hydroxide must be added to 60.0 mL of 0.978 M acetic acid in order to create a buffer with a pH of 4.59? K_a for acetic acid is 1.8 × 10^-5. A)28 g B)0.96 g C)1 g D)0 g E)2.3 g

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To create a buffer with a specific pH using acetic acid and sodium hydroxide, we use the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where pKa = -log(Ka), [A-] is the concentration of the acetate ion, and [HA] is the concentration of acetic acid. Given that the Ka for acetic acid is 1.8 × 10^-5, pKa = -log(1.8 × 10^-5) ≈ 4.74. The desired pH is 4.59, so we rearrange the equation to solve for the ratio [A-]/[HA]: 4.59 = 4.74 + log([A-]/[HA]), which gives log([A-]/[HA]) = -0.15, and thus [A-]/[HA] ≈ 0.71. Since the initial concentration of acetic acid is 0.978 M, and we want the ratio of [A-] to [HA] to be 0.71 after adding NaOH, we can set up the equation 0.978x / (0.978 - 0.978x) = 0.71, where x is the fraction of acetic acid that has been converted to acetate. Solving for x gives x ≈ 0.415. Therefore, 0.415 * 0.978 M = 0.406 M of acetic acid is converted to acetate. The volume of the solution is 60.0 mL = 0.060 L, so the moles of acetate produced are 0.406 mol/L * 0.060 L = 0.02436 mol. Since the molar mass of NaOH is approximately 40 g/mol, the mass of NaOH needed is 0.02436 mol * 40 g/mol = 0.9744 g, which rounds to 0.96 g.

What Mass of Sodium Hydroxide Must Be Added to 60