WebQuest: Take it to the Limit Use this Salts and Solubility Simulation to explore what dissolution looks like on the particle level and compare unsaturated and saturated solutions. •
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In these simulations, control the “salt” shaker to add different salts to different volumes of water. To move the shaker, drag your mouse up and down on the shaker. Select the salt from the menu at the top right of the screen. Adjust the solution volume by using the sliders on the top and bottom faucets to the left of the container. Part 1: Strontium Phosphate 1. Click the “Slightly Soluble Salts” tab to bring up a screen that looks similar to the one above. Select “strontium phosphate” and shake some of the salt into the water. a. What is the formula for strontium phosphate? Sr is in group 2A so it has a 2+ charge
PO4 is phosphate and has a 3- charge
The LCM of 2 and 3 is 6.
Multiply Sr by 3 to get 6+
Multiply PO4 by 2 to get 6Sr3(PO4)2
© KC Distance Learning b. What is the total number of strontium and phosphate ions you have added to your solution after two or three shakes? Why are there not equal numbers of cations and anions? There are 18 strontium ions and 12 phosphate. An ion is an atom or group of atoms in
which the number of electrons is not equal to the number of protons, giving it a net
positive or negative electrical charge. Due to this, an ion which is negatively charged is
attracted to the anode, which is a positive electrode in electrolysis, and is considered as
a proton. However, cations are positively charged and are attracted to cation (negative
electrode). It is know as an electron.
c. Which solution particles are not shown in the simulation? Why might this be? d. Is this solution saturated or unsaturated? How can you tell? The solution is unsaturated because more particles could still be absorbed in the
solution.
2. Add some more salt to the water until the total number of strontium ions is around 60. a. How do the particle motions begin to change? The particles started to clump together at the bottom of the container.
b. What would you expect to see on the observable level (how would this solution appear to you if you mixed this up on the kitchen counter)? I would expect to see the salt collecting at the bottom of the solution.
© KC Distance Learning 3. Add a few more shakes of the salt container or use the controls to create a solution with between 100 and 150 total strontium ions. a. Is this solution saturated or unsaturated? How can you tell? The solution is saturated because no more solvent can be dissolved in the solution.
b. What kind of interaction exists between clumped particles and particles moving freely through the solution? Some of the moving particles stick onto the clump, as if they are attracted to it.
Part2: Copper Iodide 4. Hit “reset” and select copper(II) iodide salt. Add a few shakes of salt and observe. Continue to add salt to the solution to determine the total number of particles at the saturation point for copper iodide. What is the approximate number of copper and iodide ions present at the saturation point? The approximate number of copper and iodide ions present at the saturation point is 79 copper
and 79 iodide.
5. How does the solubility of copper(II) iodide compare to the solubility of strontium phosphate? (Support your answer with a description of the particle level images) The solubility of copper(I) iodide is higher compared to the solubility level of strontium phosphate.
The strontium starts clumping at around 52 - 35 where the copper salt doesn't clump till around 70
- 70.
© KC Distance Learning