Tag: organic chemistry : some basic principles and techniques

Questions Related to organic chemistry : some basic principles and techniques

Styrene can be purified by:

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. Simple distillation

  2. Fractional distillation

  3. Vacuum distillation

  4. Steam distillation

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Correct Option: C

The standard reduction potentials of $Pt|Cr {2}O _{7}^{2-}, Cr^{+3}; Pt|MnO _{4}^{-}, Mn^{+2}; Pt|Ce^{+4}, Ce^{+3}$ in the presence of acid are 1.33 V, 1.51 V and 1.61 V, respectively, at $25^{\circ}C$. The decreasing order of oxidizing power is _________________.

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. $Cr _{2}O _{7}^{2-} > MnO _{4}^{-} > Ce^{+4}$

  2. $MnO _{4}^{-}> Cr _{2}O _{7}^{2-} > Ce^{+4}$

  3. $Ce^{+4} > MnO _{4}^{-}> Cr _{2}O _{7}^{2-}$

  4. $MnO _{4}^{-} > Ce^{+4} > Cr _{2}O _{7}^{2-}$

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Correct Option: C

Which of the following compounds can be purified by vacuum distillaiton?

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. Glycerine

  2. Glycerol

  3. Propane-$1, 2, 3$-triol

  4. Ethanol

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Correct Option: A,B,C
Explanation:

Vacuum distillation is used when the boiling point of the compound or the solvent is too high in order to distill the compound or the solvent off without significant decomposition. It is based on the fact that under vacuum the boiling point of the materials is lower than at normal atmospheric pressure. Glycerine, glycerol and propone 1,2,3-triol are the three names of the same compound. It has a boiling point of 290$^oC$ while ethanol has BP 79$^oC$ .

Option A, B and C are correct.

p-nitrophenol and o-nitrophenol are separated by?

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. Crystallisation

  2. Fractional distillation

  3. Distillation

  4. Steam distillation

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Correct Option: D

$ H _{2}O _{2}$ can be prepared by successive reactions:
$ 2NH _{4}HSO _{4}\rightarrow H _{2}+(NH _{4})^{2}S _{2}O _{8}$
$ (NH _{4}) _{2}S _{2}O _{8}+2H _{2}O \rightarrow  2NH _{4}HSO _{4}+ H _{2}O _{2}$
The first reaction is an electrolytic reaction and second is steam distillation. What amount of current would have to be used in first reaction to produce enough intermediate to yield 102 g pure $ H _{2}O _{2}$ per hour. Assume current efficiency 50 %.

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. 643.33 A

  2. 321.67 A

  3. 160.83 A

  4. 1286.67 a

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Correct Option: B

Which of the following compounds can be purified by steam distillation?

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. Salicylaldehyde

  2. Bromobenzene

  3. p-Hydroxy benzaldehyde

  4. Nitrobenzene

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Correct Option: A,B,D

Turpentine oil can be purified by:

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. steam distillation

  2. vaccum distillation

  3. fractional distillation

  4. sublimation

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Correct Option: A
Explanation:

Steam distillation of a liquid in a current of steam used especially to purify liquids that are not very volatile and are immiscible with water. The boiling point of turpentine oil is between 90 and 115 °C or 195 and 240 °F and is immiscible with water. Thus, it is purified by steam distillation.

Absolute alcohol can be prepared from rectified spirit by:

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. Azeotropic distillation with benzene

  2. Fractional distillation

  3. Keeping over fresh CaO for few hours and then distilling

  4. Distillation under reduced pressure

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Correct Option: A,C

Which of the following is not an exact differential?

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. $dq$

  2. $dG$

  3. $d(\bar { V } )$

  4. $dS$

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Correct Option: A
Explanation:
Exact differential are those function if 
$\cfrac { \delta  }{ \delta T } (\cfrac { \delta f }{ \delta P } )=\cfrac { \delta  }{ \delta P } (\cfrac { \delta f }{ \delta T } )$ where f is the function of P and T. increase of q, it will not be equal , so it will be not exact function.

A substance which decomposes at or below its boiling point cannot be purified by?

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. Steam distillation

  2. Simple distillation

  3. Fractional distillation

  4. Distillation under reduced pressure

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Correct Option: A,B,C
Explanation:

Steam distillation is used for natural aromatic compounds which are immiscible in water.
Simple and fractional distillation uses the property of difference in the boiling point. These techniques can not be used for the substance which decomposes at or below its boiling point.
Distillation under reduced pressure is basically Vaccum distillation. This method is used to boil such substances without their decomposition

Option A, B and C are the answer.