Chemistry NEET Questions — Free MCQ Practice

Chemistry MCQs for NEET — Practice Questions with Answers

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$H_{2} O_{2} r e d u c e s K_{3} [F e {(C N)}_{6}] i n :$

neutral solution

acidic solution

alkaline solution

non-polar medium

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Decomposition of $H_{2} O_{2}$ is accompanied by:

decrease in free energy

increase in free energy

no change in free energy

evolution of heat

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Explanation

Decomposition of H2O2 is a spontaneous process hence Delta G value is negatively hence decrease in Free energy will occur....

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Tellurium hydride on dissolution in water gives:

$H_{2} T e + H_{2} O ⇌ H_{3} O^{+} + H T e^{-}$

$H_{2} T e + H_{2} O ⇌ H_{3} T e^{+} + O H^{-}$

$H_{2} T e + H_{2} O \to T e O + 2 H_{2}$

None of these

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Explanation

The element is insoluble in water, but dissolves in concentrated sulphuric acid forming a deep red solution. Like sulphur and selenium, tellurium combines directly with hydrogen to form telluretted hydrogen, TeH2, an extremely objectionable smelling and highly poisonous gas, which was first prepared by ELEMENTAL H

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Among $C a H_{2}, N H_{3}, N a H a n d B_{2} H_{6}$ , which are covalent hydride?

$N H_{3} a n d B_{2} H_{6}$

$C a H_{2} a n d B_{2} H_{6}$

$N a H a n d C a H_{2}$

$N a H a n d N H_{3}$

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The acidified solution of $F e C l_{3}$ is reduced by passing:

ordinary $H_{2}$

$O_{2}$

nascent H

$H_{2}$

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Atomic hydrogen produces formaldehyde when it reacts with:

$C O_{2}$

$O_{2}$

$C_{2} H_{2}$

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The percentage of a para-hydrogen in ordinary hydrogen increases when:

temperature is lowered

temperature is increased

pressure is increased and temperature decreased

none of these

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Explanation

temperature is lowered

molecular hydrogen in which the two hydrogen nuclei are spinning in opposite directions so that their contribution to the total angular momentum is zero.

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Para- hydrogen at room temp is:

less stable than ortho- hydrogen

more stable than ortho- hydrogen

as stable as ortho- hydrogen

none of these

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Explanation

Ortho-hydrogen molecules are those in which the spins of both the nuclei are in the same direction. Para-hydrogen is when the spins of both the nuclei are in the opposite directions.

Ordinary hydrogen gas is an equilibrium mixture of ortho and para hydrogen. The amount of ortho- and para-hydrogen varies with temperature.

At 0°K, hydrogen contains mainly para-hydrogen which is more stable. At the temperature of liquid of air, the ratio of ortho- and para-hydrogen is 1 : 1.

At the room temperature, the ratio of ortho- to para-hydrogen is at its maximum of 3 : 1. Even at very high temperatures, the ratio of ortho- to para-hydrogen can never be more than 3 : 1. So, it is possible to get pure para hydrogen by cooling ordinary hydrogen gas to a very low temperature (close to 20 K) but it is never possible to get a sample of hydrogen containing more than 75% of ortho hydrogen.

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Sodium forms Na⁺ and not Na²⁺ because:

sodium contains only one electron in outermost shell

first ionisation potential is small and the difference in first and second ionisation potential is very large

radius of Na⁺ is much smaller than of Na⁺

none of the above

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Explanation

(b) It is a reason for given fact

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When sulphur is heated with NaOH(aq) the compounds formed are:

Na₂S + H₂O

Na₂SO₃ + H₂O

Na₂S + Na₂S₂O₃ + H₂O

Na₂S₂O₃ + H₂O

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Explanation

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