25.0 mL of a 0.100 mol L⁻¹ acid is to be titrated against a sodium hydroxide solution until final equivalence is reached - HSC - SSCE Chemistry - Question 16 - 2017 - Paper 1
Question 16
25.0 mL of a 0.100 mol L⁻¹ acid is to be titrated against a sodium hydroxide solution until final equivalence is reached.
Which of the following acids, if used in t... show full transcript
Worked Solution & Example Answer:25.0 mL of a 0.100 mol L⁻¹ acid is to be titrated against a sodium hydroxide solution until final equivalence is reached - HSC - SSCE Chemistry - Question 16 - 2017 - Paper 1
Step 1
Determine the number of dissociable protons
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Answer
In this case, we need to analyze the two acids:
Acetic Acid (CH₃COOH)
Acetic acid is a monoprotic acid, meaning it donates one proton (H⁺) per molecule during titration.
Citric Acid (C₆H₈O₇)
Citric acid is a triprotic acid, meaning it can donate three protons during titration.
Given that citric acid can release more protons, it will react with sodium hydroxide in a stoichiometric ratio of 1:3.
Step 2
Calculate the moles of acid
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Answer
For a given volume and concentration of acid:
The number of moles of acetic acid:
nAcetic=C×V=0.100extmolL−1×0.025extL=0.0025extmol
The number of moles of citric acid:
Since we are only given the same concentration and volume, the calculation remains the same:
nCitric=C×V=0.100extmolL−1×0.025extL=0.0025extmol
Step 3
Determine the volume of NaOH required for titration
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Answer
Using the stoichiometric ratios for the titration reactions:
For citric acid (multiplied by the stoichiometric factor of 3):
V_{NaOH, Citric} = rac{n_{Citric} × 3}{C_{NaOH}} = rac{0.0025 ext{ mol} × 3}{0.100 ext{ mol L}^{-1}} = 0.075 ext{ L} = 75 ext{ mL}
Step 4
Conclusion
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Answer
Since citric acid would require a greater volume of sodium hydroxide (75 mL) compared to acetic acid (25 mL), the acid that would require the greatest volume of sodium hydroxide is B. Citric.
