Subject

Chemistry

Class

ICSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

31.

Write balanced equations for each of the following reactions :    

(i) Dilute hydrochloric acid is added to sodium thiosulphate solution.

(ii) Sodium hydroxide solution is added to silver nitrate solution

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32.

 Explain the following with at least one example :    

(i) Keto-enol tautomerism.

(ii) Carbylamine reaction.

(iii) Rosenmund’s reduction.

(iv) Haloform reaction.


(i) In keto-enol tautomerism, a compound exists in two interconvertible form one having keto group and other having alcoholic group and a double bond. The two forms are in dynamic equilibrium with each other via proton and π electrons, for example, acetone.


(ii) Carbylamine reaction. Whan a 1° amine is heated with chloroform and ale. KOH, it forms isocyanide which has an offensive smell. The reaction is used as test for 1° amines For example3


(iii) Rosenmund’s reduction. It is a method for preparation of aldehyde by catalytic hydrogenation of acid chlorides. During reaction, H2 is passed over acid chloride in presence of Pd-BaS04 partially poisoned by sulphur or quinoline. For example,



(iv) Haloform reaction. Aldehydes and ketones having CH3-C=O group are oxidised by NaOX to give haloform and the salt of carboxylic acid. This reaction is called haloform reaction.





(iv) 
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33.

 Give one reason each for the following :  

(i) Acetone reacts with hydroxylamine to form only one product which has no geometrical isomer, but acetaldehyde reacts with hydroxylamine to form a product which has two geometrical isomers.

(ii) Direct nitration of aniline is not possible.

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34.

Write balanced equations for the preparation of:  

(i) DDT

(ii) Urotropine

(iii) Biuret

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35.

Give balanced equations for the reactions given below:    

(i) Urea is warmed with a dilute solution of sodium hydroxide.

(ii) Methyl isocyanide is warmed with dilute hydrochloric acid.

(iii) Sucrose is warmed with concentrated nitric acid.

(iv) Aniline is treated with a mixture of NaNO2 and excess ofHCl at low temperature.

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36.

 How would you convert the following :

(i) Methyl amine to ethyl amine

(ii) Benzoic acid to benzene

(iii) Glucose to fructose

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37.

Give a chemical test to distinguish between : 

(i) Urea and oxalic acid

(iiAcetaldehyde and acetone.

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38.

i) What is a specific rotation ?   

(ii) 1. What is optical activity ?

2. Name the apparatus used to measure optical activity.

3. State the two necessary conditions for a compound to show optical activity. Give one example of a compound which shows optical activity.

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39. Give the name and formula of each A, B,C, D, E and F in the following conversion reactions :  

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40. What are polyolefins ? Give the reaction for the preparation of polythene a polyolefin. 
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