Answer :
Final answer:
To determine the volume of NaOH needed to neutralize citric acid, calculate the moles of citric acid using its molarity and volume, multiply by the stoichiometric ratio to find moles of NaOH, and then divide by the molarity of NaOH to find the volume. The calculation suggests that approximately 93.4 ml of NaOH is needed, with option c) being the closest.
Explanation:
The question involves a neutralization reaction between citric acid, H₂C₄H₄O₆, and sodium hydroxide, NaOH. We will first need to write a balanced chemical equation for this acid-base reaction. Citric acid is a triprotic acid, meaning it can donate three protons (H+ ions). The general balanced equation would be:
H₂C₄H₄O₆ + 3NaOH → Na₃C₄H₄O₆ + 3H₂O
Next, we apply the stoichiometry of the reaction, which shows that 1 mole of citric acid reacts with 3 moles of NaOH. Using the molarity (M) and volume (ml) of citric acid given, we can calculate the moles of citric acid and then determine the moles of NaOH needed to neutralize it.
The number of moles of citric acid is:
Moles of H₂C₄H₄O₆ = 0.0215 L × 0.288 M = 0.006192 mol
Since the ratio of citric acid to NaOH is 1:3:
Moles of NaOH needed = 3 × 0.006192 mol = 0.018576 mol
To find the volume of 0.201 M NaOH required, we divide the moles of NaOH by its molarity:
Volume of NaOH = Moles of NaOH /Molarity of NaOH
Volume of NaOH = 0.018576 mol / 0.201 M = 0.092418 L, which is 92.418 ml. The closest option provided by the student to this calculated value is option c) 93.4 ml, making it the right choice when rounding to the nearest tenth.
