Question

Which of the following solutions will boil at the highest temperature?

A 1.0 M HNO3
B 1.0 M NaCl
C. 2.0 M CH3CH2OH
D 1.0 M CaCl2

Answer 1

Easy way is to look up the boiling points of each of these.

In general, remember that ionic bonds tend to be stronger than covalent bonds due to the coulombic attraction between ions of opposite charges (remember from grade school as they said: opposites attract).
Another thing to keep in mind is size. For instance, you have:

Answer 2

@abb0t when they say M solution, for w/e reason i'm always thinking that it's aqueous.

so it depends on the magnitude of the charges as well as the distance between them.

\[\frac{ Q _{1}q _{2} }{ r ^{2} } = F _{c}\]

I guess each molecule of CaCl2 has 1 mol of Ca, mol of 2Cl- I guess it was that I thought if it's an aqueous solution CaCl2 would produce the most moles of ions i = 3 and boil at the highest temp out of the three.

\[CaCl _{2} ---> Ca ^{2+} + 2Cl ^{-} (aq) \]

@Woodward do you also know how the columbs law applies here?

Answer 3

@Photon336 I agree with you and I think that we have to think this problem based in the colligative properties of solution assuming all of them are in the same solvent. I think that @abb0t is referring at the boiling point of the pure compounds from the list rather that the boiling point of the solutions of these compounds

Answer 4

@cuanchi the answer was D.
because whenever I see something like solution (i automatically) think that it's dissolved in water, then I thought about colliagative properties. that's how i was thinking about the question.

Answer 5

my question was about the columb's law though, when ranking the strength of ionic compounds relative to each other, do you just take into account the magnitude of the charges or the size of the atoms

Answer 6

You wouldn't be using columbs law for solution.

Answer 7

ok so that doesn't apply for solutions

Answer 8

what other cases could you use that law though? can it be used to rank the strength of ionic compounds?

Answer 9

columbs law is refers to positive and negative charges; protons and electrons. Hence, the variable, \(q\), which represents charge.

Answer 10

You can use columbs law to get a general idea between two molecules but for this type of problem, I wouldn't use it. I'd use ionic strengths and molarity.

Answer 11

ok, so like that formula is mainly used at the atomic level.

Answer 12

hmm.. C looked like an attractive answer at first for two reasons

Answer 13

the ability for the molecules to hydrogen bond

Answer 14

@abb0t reason why i get confused that formula a lot b/c ppl say you can use that to see what ionic compound is stronger by looking at the charges of the ions.

One more thing, if the explanation is molarity, and colligative properties, then i'm assuming that a molecule that produces a greater Van hoff factor i, would raise the boiling point of something higher than a molecule that had a lesser van hoff factor. i guess it's b/c the ch3chOH isn't an electrolyte,

Answer 15

Do you know what an electrolyte is? The meaning of an electrolyte?

Answer 16

if mixed with water, ethanol is not an electrolyte. It doesn't form an ion.

Answer 17

EtOH, NH\(_3\), and HAc are some of the non-aqueous solvents that are able to dissolve electrolytes.

Answer 18

I did not know the last part. thanks abb0t