Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

51.

Assertion : Trans-2-butene on reaction with Br2 gives meso-2,3-dibromobutane.

Reason : The reaction involves syn -addition of bromine.

  • If both assertion and reason are true and the reason is the correct explanation of the assertion.

  • If both assertion and reason are true and the reason is not the correct explanation of the assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


C.

If assertion is true but reason is false.

With trans-2-butene, the product of Br2 addition is optically inactive due to the formation of symmetric mesa compounds.


52.

Assertion : Benzyl bromide when kept in acetone water it produces benzyl alcohol.

Reason : The reaction follows SN2 mechanism.

  • If both assertion and reason are true and the reason is the correct explanation of the assertion.

  • If both assertion and reason are true and the reason is not the correct explanation of the assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


A.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

When benzyl bromide is kept in acetone, it produces benzyl alcohol.


53.

Subunits present in haemoglobin are

  • 2

  • 3

  • 4

  • 5


C.

4

Haemoglobin is made up of four polypeptide subunits, two alpha (α) and two beta (β) subunits. Each of the four subunits consists of a heme molecule and each of them is capable of taking up one molecule of O2. Therefore, oxyhaemoglobin can be represented as Hb(O2)4.


54.

Which one of the following is not a surfactant?

  • CH3 - (CH2)15 - (CH3)2N+ - CH3Br-

  • CH3 - (CH2)14 - CH2 - NH2

  • CH3 - (CH2)16 - CH2OSO2-Na+

  • OHC - (CH2)14 - CH2 - COO-Na+


B.

CH3 - (CH2)14 - CH2 - NH2

In order to act as a surfectant, molecule should have both polar and non-polar ends. 


55.

Assertion : Glycosides are hydrolysed in acidic conditions.

Reason : Glycosides are acetals.

  • If both assertion and reason are true and the reason is the correct explanation of the assertion.

  • If both assertion and reason are true and the reason is not the correct explanation of the assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


D.

If both assertion and reason are false.

Glycosides are formed by treating glucose with CH3OH in the presence of dry HCl gas and can be hydrolysed by strong reagents like HCN, NH2OH and C6H5NHNH2. Also, glycosides are known as hemi-acetals.


56.

Assertion : Hydroxyketones are not directly used in Grignard reaction.

Reason : Grignard reagents react with hydroxyl group.

  • If both assertion and reason are true and the reason is the correct explanation of the assertion.

  • If both assertion and reason are true and the reason is not the correct explanation of the assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


A.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

Hydroxyketones are not directly used in Grignard reaction as these are very reactive and will react with hydroxyl group.


57.

Propan-1-ol can be prepared from propene by

  • H2O/H2SO4

  • Hg(OAc)2/H2O followed by NaBH4

  • B2H6 followed by H2O2

  • CH3CO2H/H2SO4


C.

B2H6 followed by H2O2

Hydroboration yields 1° alcohol from alkenes.

3CH3CH=CH2 THFBH3 in  (CH3CH2CH2)33H2O2 3CH3CH2CH2OH1-propanol + H3BO3


58.

Time required to deposit one millimole of aluminium metal by the passage of 9.65 amperes through aqueous solution of aluminium ion is

  • 30 s

  • 10 s

  • 30,000 s

  • 10,000 s


B.

10 s

Al3+ + 3e- → Al

For deposition of 1 gm of equivalent = 96500 C

For deposition of 1 millimole = 96.500 C

As QIt ⇒ t = QI = 96.59.65 = 10 s


59.

Which one of the following is not a buffer solution?

  • 0.8M H2S + 0.8M KHS

  • 2M C6H5NH2 + 2M C6H5NH3-Br-

  • 3M H2CO3 + 3M KHCO3

  • 0.05M KClO4 + 0.05M HClO4


D.

0.05M KClO4 + 0.05M HClO4

Buffer solutions can be obtained by mixing a weak acid with its salt formed with a strong base or by mixing a weak base with its salt formed with a strong acid.

Among all the options given, option d is correct. As HClO4 is a strong acid, therefore equimolar mixture of HClO4 and its salt KClO4 is not a buffer solution.


60.

Assertion : Activity of an enzyme is pH dependent.

Reason : Change in pH affects the solubility of the enzyme in water.

  • If both assertion and reason are true and the reason is the correct explanation of the assertion.

  • If both assertion and reason are true and the reason is not the correct explanation of the assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


B.

If both assertion and reason are true and the reason is not the correct explanation of the assertion.

Enzymes are proteins which act as catalyst for bio-chemical reactions. pH affect their activity as protonation-deprotonation may cause denaturation of the protein structure. Solubility is also affected.