Question

Assertion: when NaOH is added to the HCl solution, the conductance of the solution decreases right upto the equivalence point and then increases.
Reason: At starting, fast moving to ions replaced by relatively slower moving $N{a}^{\oplus }$ ions and after the equivalence point, as $O{H}^{-}$ start increases conductance increases.

• A. Statement 1 & 2 are correct and statement 2 is correct explanation of statement 1
• B. Statement 1 & 2 are correct but statement 2 is not correct explanation of statement 1
• C. Statement 1 is true, statement 2 is false
• D. Statement 1 is false and statement 2 is true

Answer 1

The correct option is A Statement 1 & 2 are correct and statement 2 is correct explanation of statement 1

Strong Acid with a Strong Base titration, e.g. HCl with NaOH: Before NaOH is added, the conductance is high due to the presence of highly mobile hydrogen ions. When the base is added, the conductance falls due to the replacement of hydrogen ions by the added cation as H+ ions react with $O{H}^{-}$ ions to form undissociated water. This decrease in the conductance continues till the equivalence point. At the equivalence point, the solution contains only NaCl. After the equivalence point, the conductance increases due to the large conductivity of $O{H}^{-}$ ions.