Sublimation is the change of a substance directly from a solid-state to a gaseous state without getting converted into a liquid form. It is an endothermic phenomenon occurring at pressure and temperature below the triple point. Naphthalene balls, iodine, ammonium chloride, camphor and carbon dioxide undergo sublimation.
The reverse of sublimation is referred to as deposition or desublimation. In desublimation, a gaseous state substance changes directly to a solid-state without getting converted into a liquid state.
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Definition: Sublimation is the conversion of a compound directly from a solid to a gaseous state without getting converted into liquid. Naphthalene balls, iodine, ammonium chloride, camphor and carbon dioxide undergo sublimation. |
Sublimation Chemistry Questions with Solutions
Q1. Which of the following is known as the reverse of sublimation?
(a) Desublimation
(b) Solidification
(c ) Both (a) and (b)
(d) None of the above
Answer: (a) Desublimation is known as the reverse of sublimation.
Q2. Dry ice is an example of a solid that undergoes
(a) Solidification
(b) Sublimation
(c ) Both (a) and (b)
(d) None of the above
Answer: (b) Dry ice is an example of a solid that undergoes sublimation.
Q3. Which of the following state is not formed during sublimation?
(a) Solid
(b) Liquid
(c ) Gas
(d) None of the above
Answer: (b) Liquid state is not formed during sublimation.
Q4. Which of the following mixture can be separated by sublimation?
(a) Iodine and Ammonium chloride
(b) Iodine and sodium chloride
(c ) Magnesium chloride and sodium chloride
(d) Lead chloride and sodium chloride
Answer: (a) Iodine and ammonium chloride can be separated by using sublimation.
Q5. Which of the following undergo sublimation?
(a) Naphthalene balls
(b) Ammonium chloride
(c ) Carbon dioxide
(d) All of the above
(e) None of the above
Answer: (d) Naphthalene balls, ammonium chloride and carbon dioxide undergo sublimation.
Q6. What do you understand by the term sublimation?
Answer: The conversion of a compound directly from solid to gaseous state without getting converted into liquid is known as sublimation. Naphthalene balls, iodine, ammonium chloride, camphor and carbon dioxide undergo sublimation.
Q7. Why do naphthalene balls vanish with time without leaving any solid?
Answer: Naphthalene balls disappear with time without leaving any solid because they undergo sublimation, i.e. they convert directly into vapours and disappear into the air without leaving any solid.
Q8. Why does the smell of the perfume spread all around the room?
Answer: The smell of the perfume spreads all around the room because perfume particles diffuse quickly into the air, and we can sense its fragrance several miles away.
Q9. What will happen if the dry ice is at room temperature and one atmospheric pressure? Name the phenomenon involved.
Answer: Dry ice sublimes at room temperature and one atmospheric pressure without leaving any residue. Sublimation is involved.
Q10. What is dry ice? Explain its significance.
Answer: Solid carbon dioxide is known as dry ice. It does not change into the liquid state on heating but directly into the gaseous state.
Q11. Why does a substance sublime?
Answer: A substance sublimes due to heat absorption that supplies sufficient energy for molecules to overwhelm the neighbour’s attractive forces and flee into the gaseous state.
Q12. Does sublimation require heat?
Answer: Yes, sublimation requires some heat. It is an endothermic process.
Q13. Match the following.
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Column A |
Column B |
|---|---|
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Solid |
Can flow in all directions. |
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Sublimation |
The temperature at which liquid changes into the gaseous state. |
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Boiling point |
Any number of free surfaces. |
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Gases |
Gaps between particles. |
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Intermolecular space |
Change of state from solid to gas. |
Answer:
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Column A |
Column B |
|---|---|
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Solid |
Any number of free surfaces. |
|
Sublimation |
Change of state from solid to gas. |
|
Boiling point |
The temperature at which liquid changes into the gaseous state. |
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Gases |
Can flow in all directions. |
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Intermolecular space |
Gaps between particles. |
Q14. Match the following.
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Column A |
Column B |
|---|---|
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Sublimation |
Change the liquid state into vapours without reaching its boiling point. |
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Evaporation |
Heat required to change the state of 1 Kg of solid into a liquid. |
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Latent heat of vaporisation |
Heat required to change the state of 1 Kg liquid into vapours. |
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Latent heat of fusion |
Change of solid directly into vapours. |
Answer:
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Column A |
Column B |
|---|---|
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Sublimation |
Change of solid directly into vapours. |
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Evaporation |
Change the liquid state into vapours without reaching its boiling point. |
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Latent heat of vaporisation |
Heat required to change the state of 1 Kg of solid into a liquid. |
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Latent heat of fusion |
Heat required to change the state of 1 Kg liquid into vapours. |
Q15. How will you differentiate between sublimation and evaporation?
Answer: We can differentiate between sublimation and evaporation in the following ways.
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S. No. |
Sublimation |
Evaporation |
|---|---|---|
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1. |
Sublimation refers to the change of the solid form into the gaseous state. |
Evaporation refers to the change of the liquid state into the gaseous state. |
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2. |
The initial state of sublimation is solid. |
The initial state of evaporation is liquid. |
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3. |
The enthalpy of sublimation tells us about the energy required for sublimation to occur. |
The enthalpy of evaporation tells us about the energy required for evaporation to occur. |
Practise Questions on Sublimation
Q1. How will you separate a mixture of naphthalene and ammonium chloride? Instruct an activity to isolate them with a well-labelled diagram.
Q2. How will you separate a mixture of sand, iron filings, ammonium chloride and sodium chloride? Instruct an activity to isolate them.
Q3. Which substance undergoes sublimation?
Q4. Explain a good example of sublimation in everyday life?
Q5. What do you understand by the term sublimation molar heat?
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