Question

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:

List I		List II
P	$\underset{(X)}{(C_2H_5)_3N} + \underset{(Y)}{CH_3COOH}$	1	Conductivity decreases and then increases.
Q	$\underset{(X)}{KI(0.1 M)}+ \underset{(Y)}{AgNO_3(0.01 M)}$	2	Conductivity decreases and then does not change much.
R	$\underset{(X)}{CH_3COOH} + \underset{(Y)}{KOH}$	3	Conductivity increases and then does not change much.
S	$\underset{(X)}{NaOH} + \underset{(Y)}{HI}$	4	Conductivity does not change much and then increases.

• A. $(P)-(3), (Q)-(4), (R)-(2), (S)-(1)$
• B. $(P)-(4), (Q)-(3), (R)-(2), (S)-(1)$
• C. $(P)-(2), (Q)-(3), (R)-(4), (S)-(1)$
• D. $(P)-(1), (Q)-(4), (R)-(3), (S)-(2)$

Answer 1

Answer: (A)

$P: \underset{(X)}{(C_{2}H_{5})_{3}N} + \underset{(Y)}{CH_{3}COOH} \to CH_{3}COO^{-}_{(aq)} + (C_{2}H_{5})_{3}NH^{+}$
Initially conductivity increases due to ion formation after that it becomes practically constant because X alone cannot form ions.
$Q : \underset{(X)}{KI(0.1 M} + \underset{(Y)}{AgNO_{3}(0.01 M} \to AgI \downarrow +KNO_{3}$
Number of ions in the solution remains constant until all the $AgNO_{3}$ precipitated as $AgI$. Thereafter conductance increases due to increase in number of ions.
$R : \underset{(X)}{CH_{3}COOH} + \underset{(Y)}{KOH} \to CH_{3}COOK +H_{2}O$
Initially conductivity decreases due to the decrease in the number of $OH^{-}$ ions thereafter it slowly increases due to increase in number of $H^{+}$ ions.
$S : \underset{(X)}{NaOH} + \underset{(Y)}{HI} \to NaI + H_{2}O$
Initially conductivity decreases due to decrease in $H^{+}$ ions and then increases due to increase in $OH^{-}$ ions.