An aqueous solution of X is added slowly to an aqueous solution of Y as shown in List I. The variation in conductivity of these reactions is given in List II. Match List I with List II and select the correct answer using the code given below the lists:
← JEE Advanced 2013 · Paper 2
ChemistryList match+3 / -1Question 40 of 60
JEE Advanced 2013 · Paper 2, Chemistry question 40
List I
- P(X) + (Y)
- QKI (0.1 M) (X) + (0.01 M) (Y)
- R(X) + KOH (Y)
- SNaOH (X) + HI (Y)
List II
- 1Conductivity decreases and then increases
- 2Conductivity decreases and then does not change much
- 3Conductivity increases and then does not change much
- 4Conductivity does not change much and then increases
Answer and worked solution
Official answer: A
- P, Et₃N into CH₃COOH: the weak acid is barely ionised; forming the salt raises conductivity, and excess weak base adds little. → 3
- Q, KI into AgNO₃: AgI precipitates and K⁺ replaces Ag⁺ (similar mobility), so conductivity hardly changes; after the end point excess KI raises it. → 4
- R, CH₃COOH into KOH: fast OH⁻ is replaced by slower CH₃COO⁻, so conductivity falls; excess weak acid then changes it little. → 2
- S, NaOH into HI: fast H⁺ is replaced by Na⁺ (falls), then excess OH⁻ raises it. → 1
Code 3 4 2 1.
(A)