Question

$Ag$ is precipitated when $Zn$ is added to ${{\left[ Ag{{\left( CN \right)}_{2}} \right]}^{-}}$ . If $2{{\left[ Ag{{\left( CN \right)}_{2}} \right]}^{-}}+Zn\to {{\left[ Zn{{\left( CN \right)}_{4}} \right]}^{2-}}+2Ag$ is the reaction, enter 1 else 0.

Answer 1

Hint: Silver is extracted using the cyanide process where it is reduced in the form of its element from its cation with the help of some reducing agent. This process is used to extract gold and silver from their ores. It is done by dissolving the metals into the dilute solution of sodium cyanide or potassium cyanide.

Complete step by step solution:
-Metal compounds found in nature are called minerals. Minerals from which we can extract metals conveniently as well as economically are called ores. It contains impurities which are called gangue.
-Extraction of metals from ores is called metallurgy. Metals are extracted from the earth’s surface and so along with the metals, certain impurities also appear with it which needs to be removed in order to increase the efficiency of the metals.
-Gold and silver are very precious metals and are needed in a very pure form for their uses in the jewellery industries. So they have to be extracted from their ores in a better way so as to eliminate all the contaminants that can come in contact with them.
-Normal metals are extracted by converting them into oxides first and then reducing them to form the metals by various ways. This cannot be done with gold and silver as it may result in the loss of metals during the reaction which is not efficient.
-To obtain silver, cyanide method is used. It is also known as the Macarthur-forrest process. In this method, gold and silver ores are dissolved in the dilute solution of cyanides, particularly sodium cyanide or potassium cyanide.
-There are three steps of the process. The first step involves the ore containment within the cyanide solution completely. The second step involves the separation of the solids formed by the impurities from the clear solution of the metal and cyanide. The last step is the extraction of the pure metal from the solution by reduction method. The reducing agent is used for this method.
-Reaction takes place at the electrodes. Electrode where oxidation occurs is called anode and electrode where reduction occurs is called cathode. These processes are governed by electrochemical series. The top elements behave as reducing agents and as we go down, the strength of the oxidizing agents increase.
-So basically the electrochemical series governs the metals that can be used to reduce the precious metals. More electropositive metals can reduce the less electropositive metals from their ores.
-Zinc can easily reduce the silver ion and convert it into its metal form. The reaction can be shown as
$2{{\left[ Ag{{\left( CN \right)}_{2}} \right]}^{-}}+Zn\to {{\left[ Zn{{\left( CN \right)}_{4}} \right]}^{2-}}+2Ag$

Thus this reaction is correct. So 1.

Note: If there are metals which have variable valencies like copper and iron, they have different strengths of their reducing capabilities. Example - Copper is a better reducing agent when it is in (II) form rather than (I) form. So always take care of such metals while observing the reducing power.