Which has the higher boiling point, NaCl or CaCl2 ? |...

Name: Problem 16, Chapter 11: Chemistry The Science in Context
Uploaded: 2020-05-09T00:13:22-08:00
Duration: 6 min 24 s
Channel: Allea Cauilan
Description: Which has the higher boiling point, NaCl or CaCl2 ?

Key Concepts

Lattice Energy

Lattice energy is the energy that holds an ionic solid together, defined as the energy needed to break the ionic lattice into isolated ions. It depends on the magnitude of the ionic charges and the distance between the ions, with higher charges and smaller interionic distances leading to a higher lattice energy, which in turn elevates the boiling point.

Boiling Point

The boiling point is the temperature at which a substance changes from a liquid to a gas when the vapor pressure equals the external pressure. For ionic compounds, the strong ionic bonds require significant energy to break, meaning substances with higher lattice energies typically have higher boiling points.

Ionic Compounds

Ionic compounds are substances composed of positive and negative ions held together by strong electrostatic forces. This arrangement forms a crystal lattice structure that requires significant energy to disrupt, directly affecting properties such as melting and boiling points.

Transcript

00:01 Okay, this is question 16 at the end of chapter 11 in the chemistry, the science and context textbook, and it asks which has a higher highest, higher boiling point, sodium chloride or calcium chloride.

00:15 Okay.

00:15 And so in this chapter, we're talking about ion attraction, the attraction between ions, okay? and so the higher the ion attraction, the higher the boiling point.

00:26 You think about it if two ions are very attracted to each other in a compound, it would require more energy to break that ionic attraction.

00:34 So the higher the ionic attraction, the higher the boiling.

00:38 High ion attraction equals high boiling point.

00:47 Okay? and so how do we calculate ion attraction? it's e equals q1, q2 over d, where q1, q2 is your ion charge, the charge of the two ions you're looking at.

01:01 And then d is the sum of the ion radii.

01:07 Okay, the radii of the ions.

01:10 Okay, and so if we were comparing nacl and calcium chloride, right, we can calculate out e or just look at the e equation and use periodic trends to determine which one has a higher ion attraction.

01:30 Okay.

01:31 And so if we were to look at it, the ion charge for nacl, the two ions that are made are na plus and cl minus.

01:42 So you're going to plug in a plus one for q1 and a minus one for q2.

01:48 Okay.

01:50 If we were to calculate it out for calcium chloride, we make calcium 2 plus and chloride.

01:57 Okay, and the two doesn't change anything.

02:01 You don't square or put anything to the power of two or, you know, change your calculations.

02:07 But we're only looking at two of the ions that are made in the compound.

02:11 Okay, and so for calcium chloride, you would plug in q2 plus or positive 2 for q1.

02:19 And for q2, you would put a negative, a negative 1.

02:24 And so just looking at that, the numerator for our equation, the numerator for sodium chloride would end up being a negative 1.

02:35 And the numerator for calcium chloride would end up being a negative 2.

02:40 And since this is calculating out potential energy, the more negative, the more energy.

02:47 Because it's the energy that would be released if we were to break that ion attraction.

02:55 Okay.

02:56 And remember releasing energy usually ends up with a negative number.

03:00 Okay.

03:01 And so a higher value, a higher negative value would mean more energy.

03:07 Okay.

03:07 So from just analyzing the numerator, we can already see that calcium chloride has pretty much double the ion attraction...

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