JEE Main · 2023 · 01 Feb 2023 · Shift 2 · Practical and Analytical Chemistry

Which element is not present in Nessler's reagent ?

(A)Mercury
(B)Potassium
(C)Iodine
(D)Oxygen✓ Correct

Answer: (D)

Solution

Nessler's reagent is an alkaline solution of potassium tetraiodomercurate(II),

K_{2} [Hg I_{4}]

, used for the detection of ammonia. The complex is built from potassium, mercury and iodine, the three elements that constitute

K_{2} [Hg I_{4}]

. Comparing the listed elements with this formula, mercury, potassium and iodine are all present, whereas oxygen has no place in the tetraiodomercurate unit. The element absent from Nessler's reagent is oxygen.

JEE Main · 2023 · 01 Feb 2023 · Shift 2 · Single correct option

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