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ISC Class 12 Chemistry Solved Question Paper 2004

Short Answer Type

21.

Arrange the following in increasing order of acidity and name the property which decides this order :

(i) HCOOH ,CH₃ COOH, CH₂Cl COOH.

(ii) CH₃COOH, CH₃OH, C₆H₅OH.

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22. Name one ore each of tin and lead. What is the main constituent of each ?

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23. Sodium cyanide is used in the extraction of silver from its ore. Explain, why it is used and write the relevant equation.

Sodium cyanide (NaCN) is used for extracting silver from its ore due to the metal displacement property.

In this process, silver ores (Ag₂S and AgCl) are leached for many hours with an aqueous solution of NaCN. This forms soluble sodium dicyanoargentite.

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24. Write the chemical equation for the reactions involved in the extraction of copper from copper pyrites. [

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25. Discuss the structure of thiosulphate ion.

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26.

Write balanced equations for the following reactions :

(i) Tin with aqueous sodium hydroxide.

(ii) Copper with dilute nitric acid.

(iii) Bromine with sodium sulphite.

(iv) Preparation of bleaching powder.

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27.

Write the equation and name the following reactions :

(i) Acetic acid with red phosphorus and chlorine.

(ii) Acetaldehyde with aluminium ethoxide.

(iii) Phenol with acetyl chloride in the presence of AlCl₃.

(iv) Benzaldehyde with concentrated sodium hydroxide.

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28. An organic compound A on treatment with ethyl alcohol gives a carboxylic acid B and a compound C. Hydrolysis of C under acidic conditions gives B and D. Oxidation of D with KMnO₄ gives B. B on heating with Ca(OH)₂ gives E with molecular formula C₃H_sO. E reacts with 2, 4 dinitrophenyl hydrazine but does not answer Tollen’s test or react with Fehlings solution. Identify A,B, C,D and E.

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