Which solution is used for the leaching of silver metal in the p

Subject

Chemistry

Class

CBSE Class 12

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 Multiple Choice QuestionsShort Answer Type

1.

How many atoms constitute one unit cell of a face-centered cubic crystal? 

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2.

Name the method used for the refining of Nickel metal?

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3.

What is the covalency of nitrogen in N2O5

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4.

Arrange the following in increasing order of their basic strength in aqueous solution: 

 CH3NH2, (CH3)3N, (CH3)2NH

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5.

18 g of glucose, C6H12O6 (Molar Mass = 180 g mol-1) is dissolved in 1 kg of water in a saucepan. At what temperature will this solution boil? 

 (Kb for water = 0.52 K kg mol-1, boiling point of pure water = 373.15 K)

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6.

The conductivity of 0.20 M solution of KCl at 298 K is 0.025 S cm-1. Calculate its molar conductivity?

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7.

Write the dispersed phase and dispersion medium of the following colloidal systems: 

 (i) Smoke (ii) Milk

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8.

What are lyophilic and lyophobic colloids? Which of these sols can be easily coagulated on the addition of small amounts of electrolytes?

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9.

Write the differences between physisorption and chemisorption with respect to the following:

(i) Specificity

(ii) Temperature dependence

(iii) Reversibility and

(iv) Enthalpy change

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10.

Which solution is used for the leaching of silver metal in the presence of air in the metallurgy of silver? 


Dilute solution of NaCN and KCN is used for leaching of silver metal in the presence of air in the metallurgy of silver, for example in the following reaction

 

AgS + 4NaCN ⇌ 2Na[Ag(CN)2] + Na2SAgS + 4NaCN  ⇌  2Na[Ag(CN)2] + Na2S

 

The solution of sodium Argento cyanide combines with zinc dust and forms sodium tetra cyanozicate and precipitated silver. This precipitated silver is called spongy silver.

 

Zn+2Na[Ag(CN)2] →  Na2[Zn(CN)4] + 2AgZn + 2Na[Ag(CN)2] → Na2[Zn(CN)4] + 2Ag

 

The spongy silver is fused with potassium nitrate to obtain pure silver. Then the silver obtained is purified by an electrolytic process.

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