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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 ?

The cassiterite also called tinstone is the ore of tin. It contains 5 to 10% SnO₂, the rest being the impurities of sulphides of Fe and Cu.

Galena is the ore of lead. It is found associated with zinc blend, iron pyrites and traces of silver.

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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.

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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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