2[Au(CN)2]– + Zn \(\to\) [Zn(CN)4]2– + 2Au\(\downarrow\) is which of these
(A) Redox reaction
(B) Displacement reaction
(C) Combination reaction
(D) Decomposition reaction
The correct answer is A & B:
\[ 2[\text{Au(CN)}_2]^– + \text{Zn} \to [\text{Zn(CN)}_4]^{2–} + 2\text{Au} \]
This reaction involves the reduction of gold (\(Au\)) and the oxidation of zinc (\(Zn\)), making it a:
Among the following cations, the number of cations which will give characteristic precipitate in their identification tests with
\(K_4\)[Fe(CN)\(_6\)] is : \[ {Cu}^{2+}, \, {Fe}^{3+}, \, {Ba}^{2+}, \, {Ca}^{2+}, \, {NH}_4^+, \, {Mg}^{2+}, \, {Zn}^{2+} \]
A solution of aluminium chloride is electrolyzed for 30 minutes using a current of 2A. The amount of the aluminium deposited at the cathode is _________
If \( z \) is a complex number and \( k \in \mathbb{R} \), such that \( |z| = 1 \), \[ \frac{2 + k^2 z}{k + \overline{z}} = kz, \] then the maximum distance from \( k + i k^2 \) to the circle \( |z - (1 + 2i)| = 1 \) is:
Minerals are the naturally occurring, homogeneous inorganic solid substances. They are having a definite chemical composition and crystalline structure, hardness and color. For example, copper pyrite, calamine, etc.

Impurities in an ore are called gauge. The removal of a gauge from the ore is called concentration ore.
Several steps are involved in the extraction of pure metal from ores. Major steps are as follows –