Tag: chemistry

Questions Related to chemistry

Bayer's reagent is

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. $Br _{2}/CCl _{4}$

  2. Cold, dilute alkaline $KMnO _{4}$

  3. Acidified $KMnO _{4}$

  4. $O _{3}/Zn/H _{2}O$

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Correct Option: B

Acidity of fluoroform (I), bromoform (II), iodoform (III) and chloroform (IV) in decreasing order is as follows:

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. I> II> III> IV

  2. IV> III> II> I

  3. IV> I> II> III

  4. IV> I> III> II

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Correct Option: C

Which of the following is used in paint removing ?

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. $CHCl _{3}$

  2. $CH _{2}Cl _{2}$

  3. $CCl _{4}$

  4. $CH _{3}Cl$

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Correct Option: B
Explanation:

$CHCl _3$ is used as solvent and as an anaesthetic.

$CCl _4$ is used as a fire extinguisher.
$CH _2Cl _2$ is used as paint removing.
$CH _3Cl$ is used as a refrigerant.

Hence, the correct option is B.

Carbon tetrachloride is inflammable. 

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. True

  2. False

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Correct Option: B

Chocolates and fatty foods containing butter or oil sometimes leave stains on clothes that are difficult to remove. They can be removed by:

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. a solution of salt in water

  2. tetrachloroethylene

  3. water

  4. alcohol

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Correct Option: B
Explanation:

Chocolates and food strains can be removed by tetrachloroethylene. It is a colourless liquid widely used for cleaning of fabrics and therefore called 'Dry-Cleaning fluid'.

Dehydrohalogenation of alkyl halides is a common preparation method of:

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. alkenes

  2. alkanes

  3. haloalkenes

  4. both A and B

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Correct Option: A
Explanation:

Dehydrohalogenation is an organic reaction in which alkyl halide when boiled with alcoholic alkali gives corresponding alkene. It is known as elimination reaction.

Alkaline hydrolysis of 1,1,1-trichloro derivative (A) of an alkane gives a molecule (B) which produces red coloration with aqueous ${ FeCl } _{ 3 }$. The compound (A) is ?

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. ${ CH } _{ 3 }{ CH } _{ 2 }{ CCl } _{ 3 }$

  2. ${ CH } _{ 3 }{ CCl } _{ 3 }$

  3. ${ CH }{ Cl } _{ 3 }$

  4. None of these

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Correct Option: B
Explanation:
Alkaline hydrolysis of a trichloro derivative will give a carboxylic acid. The carboxylic acid that gives red colouration with aqueous $FeCl _{3}$ is acetic acid $CH _{3}COOH$. Hence, the compound  A is $CH _{3}CCl _{3}$.

Heating rubber with sulphur is known as:

chemistry manmade materials synthetic rubber rubber polymer

  1. galvanization

  2. bessemerisation

  3. vulcanization

  4. sulphonation

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Correct Option: C
Explanation:

The formation of vulcanised rubber-

To improve these physical properties,
  • water repelent
  • Less water absorption
  • Resist for oxidising agents
  • Strength
 a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415 K.On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened, The correct option is [C].

In vulcanization of rubber :

chemistry manmade materials synthetic rubber rubber polymer

  1. sulphur reacts to form a new compound

  2. sulphur cross-links are introduced

  3. sulphur forms a very thin protective layer over rubber

  4. all statements are correct

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Correct Option: B
Explanation:

Vulcanisation of rubber-

To improve these physical properties,
  • Strength
  • Resistance for oxidation
  • Repulsion from water
 a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between $373 K to 415 K.$ On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened.

The correct option is [B].

Sulphur is used in  the vulcanization of rubber.

chemistry polymer synthetic rubber rubber manmade materials

  1. True

  2. False

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Correct Option: A