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Equilibrium

Short Answer Type

51. Can equilibrium be achieved between water and its vapour in an open vessel? Explain your answer and say what happens eventually.

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Long Answer Type

52. A vessel has two compartments connected at the top. In one compartment (B), radioactive methyl iodide (CH₃I) is placed and in the other (A) normal methyl iodide (CH₃I) is placed. Will the vaporus over (A) and (B) become radioactive?
Will the radioactivity spread to the liquid in the compartment A? Discuss in terms of dynamic nature of the equilibrium between vapours and its liquid.

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53. A liquid is in equilibrium with its vapours in a sealed container at a fixed temperature. The volume of the container is suddenly increased.

(i) What is the initial effect of the change on the vapour pressure?

(ii) How do the rates of evaporation and condensation change pressure?

(iii) What happens when equilibrium is restored finally and what will be the Final vapour pressure?

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54. What are reversible and irreversible reactions? Give examples.

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55. Write a short note on the concept of chemical equilibrium.

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56. How will you recognise the equilibrium state?

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Short Answer Type

57. A reversible reaction attains equilibrium of dynamic nature. Explain.

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58. How will you demonstrate the dynamic nature of equilibrium state?

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Long Answer Type

59. Comment on the statement: Equilibrium can be approached from either direction.

This can be proved experimentally by considering the equilibrium between nitrogen tetraoxide N₂O₄ ( a colourless gas) and nitrogen dioxide NO₂ (a reddish brown gas).

It is observed that:
(i) At 298K, the two gases exist as an equilibrium having a pale brown colour.
(ii) At 273K, N₂O₄ is stable and only exists as a colourless gas.
(iii) At 373K, N₂O₄ decomposes completely into NO₂ which is reddish brown in colour.

Take two identical bulbs A and B with equal amounts of NO₂ gas and seal them. Place bulb A in an ice bath and bulb B in boiling water. After some time, the gas in bulb A (placed in an ice bath) becomes colourless showing complete conversion of NO₂ into N₂O₄. The gas in bulb B (placed in boiling water) has reddish brown colour showing completely NO₂ gas.

Now take out the bulbs A and B and transfer them to a water bath at 298K (at room temperature). The colour of the gas in bulb A starts changing into brown colour indicating the gradual conversion of N₂O₄ into NO₂.

On the other hand, the colour of the gas in bulb B beings to fade and becomes pale indicating the gradual change of NO₂ to N₂O₄.

After some time when both the bulbs attain the temperature of the water bath (i.e. 298K), the colour in the two bulbs become identical and no further change in colour takes place.

This consistency of colour shows that the equilibrium has been attained in both the cases and both the bulbs contain a mixture of NO₂ and N₂O₄ having the same composition. Thus, equilibrium can be approached from either direction.

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60. Describe in brief the characteristics of chemical equilibrium.

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