1. Which figure below best represents an aqueous solution of CaCl2?
QUESTION:
Which figure below best represents an aqueous solution of CaCl2?
Which figure below best represents an aqueous solution of CaCl2?
PAUSE
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Calcium chloride is an ionic compound. When ionic compounds are dissolved in water, the ions are dispersed throughout
the water and each one is surrounded by water molecules. In other words, the ions are individually hydrated.
In the case of calcium chloride, we expect to get kinds of ions in solution: sodium ions and chloride ions. Therefore, we can eliminate choice A since it shows only one type of particle dispersed in the solution. All the dispersed particles shown in choice A are pairs of one filled circle and one unfilled circle.
CROSS OUT choice A
Choices B, C, and D all show two kinds of dispersed particles.
In choices B and C, we see filled circles
HIGHLIGHT
and unfilled circles.
In choice D, we see unfilled circles
and pairs of filled circles.
So which one is best representation for calcium chloride in water?
Based on the formula, we expect calcium chloride to produce two chloride ions for every calcium ion.
Therefore, the best answer would be the figure where there are twice as many of one particle type compared to the other.
Therefore, the correct is choice C. There are twice as many unfilled circles shown compared to filled circles.
In choice B, there are equal numbers of filled and unfilled circles.
In choice D, there are equal numbers of unfilled circles and PAIRS of filled circles.
PAUSE END RECORDING
When ionic compounds dissolve in water, ions are dispersed and individually hydrated:
CaCl2(s)  Ca2+(aq) + 2 Cl-(aq)

2. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08