NEETprep Bank NEET Chemistry Hydrogen Questions Solved


In the preparation of hydrogenated oil the chemical reaction involving hydrogen is called:

(a) hydrogenation

(b) reduction

(c) dehydration

(d) oxidation

(a)

  1. Necessity for Hydrogenation • Hydrogenated fat is basically a substitute to butter fats. • High costs of butter fat and its poor storage stability were detrimental factors that led to the investigation of alternative sources of hard fats. • This investigation led to the invention of catalyzed H2 addition across unsaturated sites of oils and fats and was quickly commercialized. • Conversion of liquid oils to solid and semi-solid fats having wide spectrum of physical & chemical characteristics of products were thus obtained.
  2.  What is Hydrogenation? • Hydrogenation is a process that reduces unsaturated fatty acid content of triglycerides by attaching hydrogen atoms at the point of unsaturation in the presence of catalyst, usually Nickel. • Hydrogenation accomplishes two things-: • 1.It increases the melting point of the oil or fat. • 2.Resistance to oxidation and flavor deterioration. • Hydrogenation process depends on several parameters: • Pressure, Temperature, Type of catalyst, Speed of agitation etc.
  3.  MECHANISM • The mechanism involved in fat hydrogenation is believed to be the reaction between unsaturated liquid oil and atomic hydrogen adsorbed on a metal catalyst. • It is similar to hydrogenation of alkenes.

Difficulty Level:

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The most abundant isotope of hydrogen is:

(a) tritium

(b) deuterium

(c) protium

(d) para-hydrogen

(c) Protium is 1H1.

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Hydrogen is evolved by the action of cold dilute HNO3 on:

(a) Fe

(b) Mg or Mn

(c) Cu

(d) Al

(b) Only Mg and Mn react with cold dil. HNO3 to give H2.

Difficulty Level:

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A molten ionic hydride on electrolysis gives:

(a) H+ ion moving towards the cathode

(b) H+ ion moving towards the anode

(c) H2 is liberated at anode

(d) H2 is liberated at cathode

(c) Ionic hydride has H- ion.

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Which statement is not correct for hydrogen peroxide ?

(a) Pure H2O2 is fairly stable

(b) It sometimes acts as a reducing agent

(c) It acts as an oxidising agent

(d) Aqueous solution of H2O2 is weakly basic

(d) H2O2 is weak di-basic acid

Difficulty Level:

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In solid hydrogen, the intermolecular bonding is:

(a) ionic

(b) van der Waals'

(c) metallic

(d) covalent

(b) Covalent molecules occupy solid structure due to increasing van der Waals' forces.

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The lightest gas is :

(a) nitrogen

(b) helium

(c) oxygen

(d) hydrogen

(d) H2 has lowest molecular weight.

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The critical temperature of water is higher than that of O2 because H2O molecule has:

(a) fewer electrons than oxygen

(b) two covalent bonds

(c) V-shape

(d) dipole moment

(d) Dipole-dipole attraction give rise to more tendency for aggregation.

Difficulty Level:

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Benzene is oxidized by H2O2 in presence of FeSO4 to:

(a) phenol

(b) cyclohexane

(c) benzaldehyde

(d) benzoic acid

(a)

 

Difficulty Level:

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The oxidizing property of H2O2 is best explained by assuming that two oxygen atoms in its molecule are:

(a) bonded differently

(b) bonded similarly

(c) bonded covalently

(d) bonded by hydrogen bonds

(a) It is a fact

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