Destroyer #197 Gen Chem

[Pearl E. White]

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It asks for the correct order of NaCl concentration from lowest to highest in water, acetone, and hexane. I thought that the lowest amount would be water since it is an ionic compound; however, the solutions state that it would be lowest in hexane. Am I simply misunderstanding the question? Help please! Thanks in advance.

 

[DAT Destroyer]

It asks for the correct order of NaCl concentration from lowest to highest in water, acetone, and hexane. I thought that the lowest amount would be water since it is an ionic compound; however, the solutions state that it would be lowest in hexane. Am I simply misunderstanding the question? Help please! Thanks in advance.

You are indeed missing a very basic understanding. In hexane, NaCl would just sit at the bottom and do nothing. You would essentially have hexane and a blob of salt at the bottom undissociated . Since hexane is nonpolar, it would not be able to break the hydrogen bonds AND then compensate the new bonds with similar energy balance. In water, we see the opposite . The polar water breaks the NaCl lattice nicely, and distributes NaCl as Na+ and Cl- throughout the entire solution. In acetone, it is only fairly soluble since we have a solvent with far less polarity than water.

I hope this helps. Keep hammering away !

Dr. Romano

 

[Pearl E. White]

You are indeed missing a very basic understanding. In hexane, NaCl would just sit at the bottom and do nothing. You would essentially have hexane and a blob of salt at the bottom undissociated . Since hexane is nonpolar, it would not be able to break the hydrogen bonds AND then compensate the new bonds with similar energy balance. In water, we see the opposite . The polar water breaks the NaCl lattice nicely, and distributes NaCl as Na+ and Cl- throughout the entire solution. In acetone, it is only fairly soluble since we have a solvent with far less polarity than water.

I hope this helps. Keep hammering away !

Dr. Romano

So, wouldn't the highest concentration of NaCl be in hexane? The answer says it should go hexane<acetone<water. That's where my confusion is.

 

[yoh95]

So, wouldn't the highest concentration of NaCl be in hexane? The answer says it should go hexane<acetone<water. That's where my confusion is.

No, NaCl is NOT dissociating in hexane

 

[spdental]

So, wouldn't the highest concentration of NaCl be in hexane? The answer says it should go hexane<acetone<water. That's where my confusion is.

The highest concentration would not be in hexane, as it didn't react with the hexane. To be in something it would need to dissociate into it's ions (such as in the water).

 

[drobgyn32]

NaCl - ionic and polar, so would dissociate.
Water = polar
Hexane =nonpolar

NaCl in water - dissociates
NaCl in hexane - does not dissociate

So IN SOLUTION, water has the most NaCl, whereas in hexane, since it did not dissociate, most just sits at the bottom, with very little in the actual solution.

 

[Pearl E. White]

Thanks everyone. I understood when it dissolves/when it doesn't. I just wasn't familiar with the IN SOLUTION part lol. I was thinking well in hexane it doesn't dissociate into ions so that has the most solid NaCl. Thanks for clearing that up. I promise I'm not crazy 😉

 

[DAT Destroyer]

Thanks everyone. I understood when it dissolves/when it doesn't. I just wasn't familiar with the IN SOLUTION part lol. I was thinking well in hexane it doesn't dissociate into ions so that has the most solid NaCl. Thanks for clearing that up. I promise I'm not crazy 😉

Hooray, you got it! Glad you could help and never hesitate to post questions, we do our best to answer asap.

nancy