Tag: methods of purification - organic compounds

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

Styrene can be purified by:

  1. Simple distillation

  2. Fractional distillation

  3. Vacuum distillation

  4. Steam distillation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Styrene is heat-sensitive and tends to polymerize at its normal boiling point. Therefore, it must be purified by vacuum distillation to lower its boiling point.

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

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 _________________.

  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. $MnO _{4}^{-} > Ce^{+4} > Cr _{2}O _{7}^{2-}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Oxidizing power is directly proportional to the standard reduction potential. The values are Ce4+ (1.61 V) > MnO4- (1.51 V) > Cr2O7 2- (1.33 V).

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

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

  1. Glycerine

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

  4. Ethanol
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
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.

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

p-nitrophenol and o-nitrophenol are separated by?

  1. Crystallisation

  2. Fractional distillation

  3. Distillation

  4. Steam distillation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

o-Nitrophenol exhibits intramolecular hydrogen bonding, making it more volatile than p-nitrophenol, which exhibits intermolecular hydrogen bonding. Steam distillation exploits this difference in volatility.

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

$ 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 %.

  1. 643.33 A

  2. 321.67 A

  3. 160.83 A

  4. 1286.67 a
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

102 g H2O2 is 3 moles. The reaction produces 1 mole H2O2 per mole of (NH4)2S2O8. Electrolysis requires 2 moles of electrons per mole of persulfate. Total electrons = 6 moles. Faraday = 96500 C. Q = 6 * 96500 = 579,000 C. Current = Q/t = 579,000 / 3600 = 160.83 A. With 50% efficiency, I = 160.83 / 0.5 = 321.67 A.

Multiple choice bio-chemistry biochemical techniques methods of purification of organic compounds methods of purification - organic compounds chromatography

Osazone formation is used to separate and identify.

  1. Alcohols

  2. Carboxylic acids

  3. Carbohydrates

  4. Starch
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Osazones are characteristic crystalline derivatives formed by the reaction of reducing sugars (carbohydrates) with phenylhydrazine. They are used to identify specific sugars.

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

Turpentine oil can be purified by:

  1. steam distillation

  2. vaccum distillation

  3. fractional distillation

  4. sublimation
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice bio-chemistry biochemical techniques methods of purification of organic compounds methods of purification - organic compounds chromatography

A mixture of camphor and benzoic acid can be easily separated by?

  1. Sublimation

  2. Fractional distillation

  3. Chemical method

  4. Extraction with solvents
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aqueous solution of $NaHCO _3$ can be used to separate benzoic acid from its mixture with camphor. Benzoic acid forms water soluble sodium benzoate with $NaHCO _3$. So, A mixture of camphor and benzoic acid can be easily separated by Chemical method.

Option C is correct.