Assertion (A) Cu^ 2+ and Cd^ 2+ are separated by first adding KCN solution and then passing H_ 2 ~S gas. Reason (R) KCN reduces Cu^ 2+ to Cu^ + and forms a complex with it. The correct answer is

Correct answer: B. Both (A) and (R) are true but (R) is not the correct explanation of (A) KCN forms complex with Cu^ + and Cd^ 2+ as K_ 3 [Cu(CN)_ 4 ] and K_ 2 [Cd(CN)_ 4 ] respectively. On passing H_ 2 ~S , only Cd^ 2+ complex gets decomposed to yellow CDS.

NEET

Exam: NEET
Subject: Chemistry
Chapter: Practical Chemistry

NEET · Chemistry · Practical Chemistry

Assertion (A) Cu^ 2+ and Cd^ 2+ are separated by first adding KCN...

Assertion (A)

\mathrm{Cu}^{2+}

and

\mathrm{Cd}^{2+}

are separated by first adding

\mathrm{KCN}

solution and then passing

\mathrm{H}_{2} \mathrm{~S}

gas. Reason (R)

\mathrm{KCN}

reduces

\mathrm{Cu}^{2+}

\mathrm{Cu}^{+}

and forms a complex with it. The correct answer is

Options

ABoth (A) and (R) are true and (R) is the correct explanation of (A)
BBoth (A) and (R) are true but (R) is not the correct explanation of (A)
C(A) is true but (R) is not true
D(A) is not true but (R) is true

Correct answer

B. Both (A) and (R) are true but (R) is not the correct explanation of (A)

Step-by-step solution

\mathrm{KCN}

forms complex with

\mathrm{Cu}^{+}

and

\mathrm{Cd}^{2+}

\mathrm{K}_{3}\left[\mathrm{Cu}(\mathrm{CN})_{4}\right]

and

\mathrm{K}_{2}\left[\mathrm{Cd}(\mathrm{CN})_{4}\right]

respectively. On passing

\mathrm{H}_{2} \mathrm{~S}

, only

\mathrm{Cd}^{2+}

complex gets decomposed to yellow CDS.

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