Tag: biochemical techniques

Quizzes (6) Questions (139)

Questions Related to biochemical techniques

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

Which is/are the correct method for separating a mixture of benzoic acid, p-methylaniline & phenol.

  1. $\xrightarrow {aq.NaHCO _3}$ $ \xrightarrow {aq.NaOH}$
  2. $\xrightarrow {aq.HCl}$ $ \xrightarrow {aq.NaHCO _3}$
  3. $\xrightarrow {aq.NaOH}$ $\xrightarrow {aq.NaHCO _3}$
  4. $\xrightarrow {aq.NaOH}$ $ \xrightarrow {aq.HCl}$
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Multiple choice chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

Assertion: 

A mixture of acetone and methanol can be separated by fractional distillation 

Reason: 
The difference between their boiling point is very less

  1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

  2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

  3. Assertion is correct but Reason is incorrect

  4. Both Assertion and Reason are incorrect
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
A mixture of acetone and methanol both are polar therefore they are miscible and can interact with each other by H-bonding. 
The boiling point of Methanol is 64.7 $^o$C and boiling point of Acetone is 56 $^o$C.
So, it is very easy to separate them by fractional distillation.

Thus, Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
Hence, the correct option is $\text{A}$
Multiple choice chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques
By reducing the pressure in the container, the boiling point of liquids in the mixture can be reduced and the mixture can be distilled at a lower temperature. This technique is called:

  1. vacuum distillation

  2. steam distillation

  3. fractional distillation

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Vacuum distillation is a method of distillation whereby the pressure above the liquid mixture to be distilled is reduced to less than its vapour pressure causing evaporation of the most volatile liquids.

Steam distillation is a special type of distillation for temperature sensitive materials like natural aromatic compounds. Many organic compounds tend to decompose at high sustained temperatures. Separation by distillation at the normal (1 atmosphere) boiling points is not an option, so water or steam is introduced into the distillation apparatus. 

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 is not a product of tar distillation?

  1. Phenol & naphthalene

  2. Benzol & pitch

  3. Anthracene & creosote

  4. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The distillation of tar do not give Phenol & naphthalene, or Benzol & pitch or Anthracene & creosote.

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.