Improve Your Chemistry Skills with this Free Quiz - Check it Out Now!

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Discussion Overview

The discussion revolves around a chemistry quiz, specifically addressing the accuracy of answers related to solubility and boiling points of various compounds. Participants explore concepts of ionic compounds, intermolecular forces, and the behavior of substances in water.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants note that there are errors in the quiz answers, but specifics are not always provided.
  • There is a discussion about whether CaO dissolves in water, with some arguing that it does due to its ionic nature and the polarity of water.
  • Others suggest that the behavior of compounds in water can involve reactions rather than simple dissolution.
  • The boiling point is discussed in terms of vapor pressure, with participants explaining that it increases when a substance is dissolved due to lowered vapor pressure.
  • One participant challenges the assumption that all inorganic compounds are purely ionic and highlights exceptions, such as calcium silicate.

Areas of Agreement / Disagreement

Participants express differing views on the solubility of CaO and the interpretation of the quiz answers. There is no consensus on the correctness of specific answers or the underlying chemistry principles.

Contextual Notes

Some participants reference specific compounds and their behaviors, but there is a lack of clarity on certain assumptions and definitions, particularly regarding ionic versus covalent characteristics in solubility contexts.

Shackleford
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See link.

http://ls1tech.com/forums/attachment.php?attachmentid=138166&d=1214890282
 
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Just skimmed - mostly OK, but at least one obvious error.
 
Borek said:
Just skimmed - mostly OK, but at least one obvious error.

Hmm. I finished this late last night. What's the obvious error?
 
Sorry, you will not get it from me, unless you are ready to split your grade :wink:
 
Borek said:
Sorry, you will not get it from me, unless you are ready to split your grade :wink:

I can get it from you. This is an open-notes, open-book, open-person, take-home quiz. Just tell me the numbers, and I'll take a look at them.
 
Well, for starters, one of your answers in 1) is wrong...
 
Huh, missed that one.

Which means there is still another mistake on the other end :wink:
 
chemisttree said:
Well, for starters, one of your answers in 1) is wrong...

I don't see that one is wrong. Molecules with similar intermolecular forces will dissolve each other. Ionic compounds require polar molecules to dissolve. As far as I can tell, my answers reflect that. I also looked over the rest and didn't catch any error. I'll need a little more than there's just one wrong.
 
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Does CaO dissolve in water?

What is boiling? When does the liquid boil and why?
 
  • #10
Borek said:
Does CaO dissolve in water?

What is boiling? When does the liquid boil and why?

I don't see CaO and water in number one.

The boiling point is when the vapor pressure equals or exceeds the atmospheric pressure.
 
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  • #11
I never told there is CaO in number one, I just asked whether CaO dissolves in water. If CaO doesn't suit you, you may answer question about Na2O solubility :wink:

The boiling point is when the vapor pressure equals or exceeds the atmospheric pressure.

That's correct. Now, why does the boiling point go up when you dissolve some substance?
 
  • #12
Borek said:
I never told there is CaO in number one, I just asked whether CaO dissolves in water. If CaO doesn't suit you, you may answer question about Na2 solubility.
That's correct. Now, why does the boiling point go up when you dissolve some substance?

I would say CaO does dissolve in water. It's an ionic compound, and they require a polar molecule in which to dissolve. A water molecule is polar.

The boiling point goes up because the vapor pressure is lowered. It requires more energy input to extract the molecules from the solution.
 
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  • #13
Shackleford said:
I would say CaO does dissolve in water. It's an ionic compound, and they require a polar molecule in which to dissolve. A water molecule is polar.

No, this is chemistry, sometimes instead of dissolving things react or don't react.

The boiling point goes up because the vapor pressure is lowered. It requires more energy input to extract the molecules from the solution.

Correct. What will happen to the vapor pressure when you dissolve more substance?
 
  • #14
Borek said:
No, this is chemistry, sometimes instead of dissolving things react or don't react.



Correct. What will happen to the vapor pressure when you dissolve more substance?

It'll lower more until it becomes saturated.
 
  • #15
Anyone else?
 
  • #16
You were given many hints. Have you checked what happens to CaO in water? Have you checked what is the chemistry of the only oxide present on the question sheet? Have you checked answers that deal with the changes in boiling point or vapor pressure?
 
  • #17
Borek said:
You were given many hints. Have you checked what happens to CaO in water? Have you checked what is the chemistry of the only oxide present on the question sheet? Have you checked answers that deal with the changes in boiling point or vapor pressure?

At the risk of sounding redundant, I already said I looked over the problems and didn't catch any mistakes. I took the first CHEM course over two years ago.
 
  • #18
Shackleford said:
I don't see that one is wrong. Molecules with similar intermolecular forces will dissolve each other. Ionic compounds require polar molecules to dissolve. As far as I can tell, my answers reflect that. I also looked over the rest and didn't catch any error. I'll need a little more than there's just one wrong.

You are making the (wrong) assumption that all inorganic compounds are purely ionic compounds and that they ionize completely (or mostly) in water. Calcium silicate (a major component in hydrated portland cement) is an example of an inorganic compound that has largely but not entirely ionic bonds. It does not dissolve appreciably in water. Calcium silicate is not on your list but I'll bet you can quickly find the compound that I was referring to.

Hint: Bayer process
 

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