JEE Advanced · Chemistry · 31. Practical Chemistry

The pair(s) of ions where BOTH the ions are precipitated upon passing $H_{2} S$ gas in presence of dilute HCl, is (are)

A $B a^{2 +}, Z n^{2 +}$
B $B i^{3 +}, F e^{3 +}$
C $C u^{2 +}, P b^{2 +}$
D $H g^{2 +}, B i^{3 +}$

Verified Solution

Answer & Solution

Correct Answer

(D) $H g^{2 +}, B i^{3 +}$

Step-by-step Solution

Detailed explanation

Precipitate is formed on passing

H_{2} S

in acidic medium i.e., ion must be of group II.

C u^{2 +}, P b^{2 +}, H g^{2 +}, B i^{3 +}

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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From JEE Advanced

Consider the kinetic data given in the following table for the reaction

A + B + C \to

Product.

Ex peri ment No.	$[\text A]$ $(\text{mol}$ $\text{dm} ^{-3})$	$[\text B]$ $(\text{mol}$ $\text{dm} ^{-3})$	$[\text C]$ $(\text{mol}$ $\text{dm} ^{-3})$	Rate of reaction $(\text{mol}$ $\text{dm} ^{-3}$ $\text s^{-1})$
1	0.2	0.1	0.1	$6.0 \times$ $10^{-5}$
2	0.2	0.2	0.1	$6.0 \times $ $10^{-5}$
3	0.2	0.1	0.2	$1.2 \times $ $10^{-4}$
4	0.3	0.1	0.1	$9.0 \times $ $10^{-5}$

The rate of the reaction for

[A] = 0.15 m o l d m^{- 3}, [B] = 0.25 m o l d m^{- 3}

and

[C] = 0.15 m o l d m^{- 3}

is found to be

Y \times 10^{- 5} m o l d m^{- 3} s^{- 1} .

The value of

Y

is __________

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Ex peri ment No.	\([\text A]\) \((\text{mol}\) \(\text{dm} ^{-3})\)	\([\text B]\) \((\text{mol}\) \(\text{dm} ^{-3})\)	\([\text C]\) \((\text{mol}\) \(\text{dm} ^{-3})\)	Rate of reaction \((\text{mol}\) \(\text{dm} ^{-3}\) \(\text s^{-1})\)
1	0.2	0.1	0.1	\(6.0 \times\) \(10^{-5}\)
2	0.2	0.2	0.1	\(6.0 \times \) \(10^{-5}\)
3	0.2	0.1	0.2	\(1.2 \times \) \(10^{-4}\)
4	0.3	0.1	0.1	\(9.0 \times \) \(10^{-5}\)

The pair(s) of ions where BOTH the ions are precipitated upon passing H2S gas in presence of dilute HCl, is (are)

Step-by-step Solution

The pair(s) of ions where BOTH the ions are precipitated upon passing $H_{2} S$ gas in presence of dilute HCl, is (are)