Chem questions

[Fighter127]

1. Would the freezing point depression be different for a volatile than for a non-volatile solute? Explain how it would be different.

2. Explain why benzophenone is a solid at room temperature and why cyclohexanone is a liquid at room temperature.

tried looking everywhere to find the answers to these and had no luck.

---

Members don't see this ad.

 

[labqi]

I'll hazard to take a guess.
1. Volatile means more likely to become a gas. A non-volatile more like to stay in it's current configuration. If placed in solution I think both would decrease freezing point regardless of their volatility. Perhaps, the more volatile one would have a higher fp/mp as it has a higher likely hood to evaporate or leave the substance.

2. Resonance? More double bonds, more likely to stay a solid state.

I'm not sure. Tough questions.

 

[benjaminl1nus]

2) benzophenone is an aromatic compound, with a higher MW than cyclohexanone. higher MW --> more electrons --> Stronger IMFs. It has more opportunities to interact in an intermolecular fashion (via dispersion forces) than cyclohexanone. this is most likely why it's solid at room temp.

 

[DrknoSDN]

Ben is right about 2. Benzophenone is aromatic with higher MW causing greater IMFs.

In addition to the IMFs, cyclohexane is not flat while Benzophenone is. The aromatic properties force the flat structure letting the molecules pack together well and raise the MP/BP. The space filling models help more easily visualize the packing difference.

Cyclohexane:

Benzophenone:

 

[chenzt]

In addition to the IMFs, cyclohexane is not flat while Benzophenone is. The aromatic properties force the flat structure letting the molecules pack together well and raise the MP/BP. The space filling models help more easily visualize the packing difference.

If you compare the BP/MP of benzene and cyclohexane, there's barely a difference. I don't think this packing have much of an effect. In fact, cyclohexane has the higher BP/MP.

Benzene is denser, however.