NEET Questions Solved


The lightest gas is :

(a) nitrogen

(b) helium

(c) oxygen

(d) hydrogen

(d) H2 has lowest molecular weight.

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Atomic hydrogen is obtained by:

(a) electrolysis of heavy water

(b) reaction of water with heavy metals

(c) thermal decomposition of water

(d) passing silent electric discharge through hydrogen at low pressure

(d) Atomic hydrogen is obtained by passing ordinary hydrogen through an electric arc.

              H2arc, 200°CElectric2H; H=104.5 kcal mol-1

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Para hydrogen is:

(a) less stable than ortho hydrogen

(b) more stable than ortho hydrogen

(c) as stable as ortho hydrogen

(d) none of the above

(a) Ortho-hydrogen is more stable and para form always try to convert in ortho form.

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What is formed when calcium carbide reacts with heavy water?

(a) C2D2

(b) CaD2

(c) Ca2D2O

(d) CD2

(a) CaC2 + 2D2O         Ca(OD)2 + C2D2

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Under what condition of temperature and pressure the formation of atomic hydrogen from molecular hydrogen will be favoured most?

(a) High temperature and high pressure

(b) Low temperature and low pressure

(c) High temperature and low pressure

(d) Low temperature and high pressure

(c) H2           H + H;            H=+ve

The forward reaction is favoured by low pressure and high temperature. Follow Le-Chatelier's principle.

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The ortho and para hydrogen possess:

(a) same physical properties but different chemical properties

(b) different physical properties but same chemical properties

(c) same chemical and physical properties

(d) different physical and chemical properties

(b) Ortho and para-hydrogen possess same electronic arrangement but different spin of nuclei.

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Hydrogen absorbed on palladium is known as:

(a) atomic H

(b) nascent H

(c) occluded H

(d) heavy H

(c) Some transition metals such as Pt, Ni, Pd, Os, Cr, Mn, Fe, etc., absorb relatively large amount of hydrogen gas, which is called occluded hydrogen.

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Poorest reducing agent among following is

(1) atomic hydrogen

(2) nascent hydrogen

(3) dihydrogen

(4) all have same reducing strength

(3) Fact

 

nascent hydrogen - newly born hydrogen is  not stable form of hydrogen, it is very reactive and immediately reduce the metal or convert into molecular hydrogen.

hydrogen molecule  is most stable form of hydrogen in free state. This is because the energy of hydrogen molecule is very high, 104 Kcal/mole.

 

A hydrogen atom is electrically neutral but the presence of  unpaired electron makes it highly reactive. The hydrogen atom can either lose the electron and convert into a proton or accpet a second electron and acquire stable duplet configuration like that of Helium. Either way, the atomic hydrogen never stays stable with its unpaired electron which can act like a free radical.

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NEET - 2016

Which of the following statements about hydrogen is incorrect?

(a) Hydrogen never acts as cation in Ionic salts

(b) Hydronium ion ,H3O+ exists freely in solution

(c) Dihydrogen does not act as a reducing agent

(d) Hydrogen has three isotopes of which tritium is the most common

(c,d) 

For ionic salts, hydrogen never behaves as cation, but behaves as anion (H-).

H3O+ exists freely in solution.

Dihydrogen acts as a reducing agent.

Hydrogen has three isotopes.

Protium(11H)

Deuterium (21 H)

Tritium (31 H)

Protium is the most common isotopes of hydrogen with an abundance of 99.98%.

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Nascent hydrogen consists of -

(A) Hydrogen atoms with excess energy

(B) Hydrogen molecules with excess energy

(C) Hydrogen ions in the excited state

(D) Solvated protons

(A).  Hydrogen atoms with excess energy

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