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Oxygen is smaller in size and thus due to its small size complete its octet by forming pπ = p<span id=MathJax-Element-2-Frame class=mjx-chtml MathJax_CHTML style=padding: 1px 0px; margin: 0px; box-sizing: border-box; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 16.66px; letter-spacing: normal; word-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative; tabindex=0 role=presentation data-mathml='<math xmlns=http://www.w3.org/1998/Math/MathML><mi mathvariant=normal>π</mi></math>'> π bond. Therefore, O 2 is a discrte molecule and the intermolecular forces of attraction are weak vander waals forces. Hence, O 2 is a gas. While sulphur is large in size, cannot form p<span id=MathJax-Element-3-Frame class=mjx-chtml MathJax_CHTML style=padding: 1px 0px; margin: 0px; box-sizing: border-box; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 16.66px; letter-spacing: normal; word-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative; tabindex=0 role=presentation data-mathml='<math xmlns=http://www.w3.org/1998/Math/MathML><mi mathvariant=normal>π</mi></math>'> π = p<span id=MathJax-Element-4-Frame class=mjx-chtml MathJax_CHTML style=padding: 1px 0px; margin: 0px; box-sizing: border-box; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 16.66px; letter-spacing: normal; word-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative; tabindex=0 role=presentation data-mathml='<math xmlns=http://www.w3.org/1998/Math/MathML><mi mathvariant=normal>π</mi></math>'> π bonds. Therefore, in order to gain stability, it exists as S 8 which is a solid.

Subject

Chemistry

Class

CBSE Class 12

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CBSE Class 12 Chemistry Solved Question Paper 2018

Short Answer Type

21.

A first-order reaction is 50% completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction.

(Given: log 2 = 0.3010, log 4 = 0.6021, R = 8.314 JK^–1 mol^–1)

22.

What happens when

A freshly prepared precipitate of Fe(OH)₃ is shaken with a small amount of FeCl₃ solution?

23.

What happens when

Persistent dialysis of a colloidal solution is carried out?

24.

What happens when

An emulsion is centrifuged?

25.

For the reaction

$2 A g C l (s) + H_{2} (g) (1 a t m) \overset{}{\to} 2 A g (s) + 2 H^{+} (0.1 M) + 2 C l^{-} (0.1 M), ∆ G^{o} = - 43600 J a t 25^{o} C$

Calculate the e.m.f. of the cell.
[log 10^–n = – n]

26.

Define fuel cell and write its two advantages.

27.

Give reasons:

H₃PO₃undergoes disproportionation reaction but H₃PO₄ does not.

28.

Give reason:

When Cl₂ reacts with an excess of F₂. ClF₃ is formed and not FCl₃

29.
Give Reason:
Dioxygen is a gas while Sulphur is a solid at room temperature.

Oxygen is smaller in size and thus due to its small size complete its octet by forming pπ = p $π$ bond. Therefore, O₂ is a discrte molecule and the intermolecular forces of attraction are weak vander waals forces. Hence, O₂ is a gas. While sulphur is large in size, cannot form p $π$ = p $π$ bonds. Therefore, in order to gain stability, it exists as S₈ which is a solid.