Chimactiv - Interactive numerical educational resources for the analysis of complex media

Exercise 1: Conductivity evolution during a titration

Find the curve corresponding to the evolution of conductivity during the titrations listed below (by dragging and dropping the suitable label on the right curve). 𝜆° (H₃O⁺) > 𝜆° (HO^-). It is assumed that:

𝜆° (weak acid AH₂⁺) < 𝜆° (weak acid AH⁺) < 𝜆° (weak base A^-)

Strong acid – Strong base H₃O⁺ + HO^- ⇄ H₂O Congratulations: conductivity strongly decreases before the equivalence point (consumption of H₃O⁺) and increases sharply after the equivalence point (HO^- in excess) 𝜆° (H₃O⁺) > 𝜆° (HO^-)	Weak acid (neutral) – strong base AH + HO^- ⇄ A^- + H₂O Congratulations: conductivity slowly increases before the equivalence point (formation of A^-) and increases sharply after the equivalence point (HO^- in excess) 𝜆° (HO^-) >> 𝜆° (A^-) 𝜆° (AH₂⁺) < 𝜆° (A^-)	Weak acid (ionic) – strong base AH⁺ + HO^- ⇄ A + H₂O Congratulations: conductivity slowly decreases before the equivalence point (consumption of AH⁺) and increases sharply after the equivalence point (HO^- in excess) 𝜆° (HO^-) >> 𝜆° (AH⁺) 𝜆° (AH⁺) < 𝜆° (A^-)
Strong base- Strong acid HO^- + H₃O⁺ ⇄ H₂O Congratulations: conductivity strongly decreases before the equivalence point (consumption of HO^-) and increases sharply after the equivalence point (H₃O⁺ in excess) 𝜆° (H₃O⁺) > 𝜆° (HO^-)	Weak base (ionic) – strong acid A^- + H₃O⁺ ⇄ AH + H₂O Congratulations: conductivity slowly decreases before the equivalence point (consumption of A^-) and increases sharply after the equivalence point (H₃O⁺ in excess) 𝜆° (H₃O⁺) >> 𝜆° (A^-) 𝜆° (AH⁺) < 𝜆° (A^-)	Weak base (neutral) – strong acid AH + H₃O⁺ ⇄ AH₂⁺ + H₂O Congratulations: conductivity slowly increases before the equivalence point (formation of AH₂⁺) and increases sharply after the equivalence point (H₃O⁺ in excess) 𝜆° (H₃O⁺) >> 𝜆° (AH₂⁺) 𝜆° (AH₂⁺) < 𝜆° (A^-)

How to use a conductivity meter

Exercise 1: Conductivity evolution during a titration

H3O+ + HO- ⇄ H2O

AH + HO- ⇄ A- + H2O

AH+ + HO- ⇄ A + H2O

HO- + H3O+ ⇄ H2O

A- + H3O+ ⇄ AH + H2O

AH + H3O+ ⇄ AH2+ + H2O

H₃O⁺ + HO^- ⇄ H₂O

AH + HO^- ⇄ A^- + H₂O

AH⁺ + HO^- ⇄ A + H₂O

HO^- + H₃O⁺ ⇄ H₂O

A^- + H₃O⁺ ⇄ AH + H₂O

AH + H₃O⁺ ⇄ AH₂⁺ + H₂O