Why is CN stable in low pressure but unstable otherwise?

In summary, CN is a free radical with 1 unpaired valence electron. This makes it highly reactive and unstable under normal terrestrial conditions due to increased collision frequencies and shorter mean free paths. However, in comets where pressure is extremely low, CN can persist due to the lack of collisions and longer mean free paths.
  • #1
zachem62
37
3
Here's the question:
The CN molecule has been observed spectroscopically in comets where pressure has been estimated to be as low as 10–10 mm Hg. Draw a Lewis structure for CN. Suggest an explanation as to why this species can persist in a comet but is unstable under normal terrestrial conditions.

The only progress I could make was to realize that CN is a free radical since it has 1 unpaired valence electron. And if I understand the question correctly, CN is stable under conditions of extremely low pressure but unstable at normal conditions of higher pressure, and its asking why this is, and I'm kind of clueless. Please help! Thanks.
 
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  • #2
zachem62 said:
CN is a free radical since it has 1 unpaired valence electron
... and, what happens to free radicals at higher pressures? Think about collision frequencies, kinetic theory of gases, mean free path ...
 
  • #3
Bystander said:
... and, what happens to free radicals at higher pressures? Think about collision frequencies, kinetic theory of gases, mean free path ...

They're unstable at higher pressures?
 
  • #4
zachem62 said:
it has 1 unpaired valence electron
What do unpaired electrons do?
 
  • #5
Bystander said:
What do unpaired electrons do?
well, the atom with an unpaired electron would be highly reactive
 
  • #6
zachem62 said:
well, the atom with an unpaired electron would be highly reactive

Why do you stop here? Try to draw conclusions from what you just wrote and from what Bystander wrote in the post #2.
 

Related to Why is CN stable in low pressure but unstable otherwise?

1. Why is CN stable in low pressure but unstable otherwise?

The stability of CN (cyanide) in different pressure conditions is determined by its molecular structure. In low pressure, CN is stable because the bond between the carbon and nitrogen atoms is relatively weak, making it easier for the molecule to break apart. However, in high pressure, the bond becomes stronger, resulting in a more stable molecule that is difficult to break apart.

2. What is the role of pressure on the stability of CN?

Pressure affects the stability of CN by altering the strength of the bond between carbon and nitrogen atoms. In low pressure, the bond is weaker, making CN more likely to dissociate into its individual atoms. On the other hand, high pressure strengthens the bond, making the molecule more stable and less likely to dissociate.

3. How does the stability of CN change with increasing pressure?

As pressure increases, the stability of CN also increases. This is because the bond between the carbon and nitrogen atoms becomes stronger, making it more difficult for the molecule to break apart. Therefore, CN is more stable in high pressure environments compared to low pressure ones.

4. Why is CN considered an unstable molecule?

CN is considered an unstable molecule because it has a relatively weak bond between the carbon and nitrogen atoms. This means that under certain conditions, such as high pressure, the molecule can easily break apart into its individual atoms. Additionally, CN is reactive and can readily react with other molecules, further contributing to its instability.

5. Can CN be stable under all pressure conditions?

No, CN cannot be stable under all pressure conditions. It is only stable in low pressure environments where the bond between carbon and nitrogen atoms is relatively weak. In high pressure environments, the bond becomes stronger, making CN more unstable and prone to dissociation. Therefore, the stability of CN is highly dependent on the pressure conditions it is exposed to.

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