CHEM 102 L General Chemistry II

Learning Goals: Students will be able to:

· Calculate Q.

· Predict what would be observed on a macroscopic level to a solution by comparing Q to Ksp.

· Use microscopic illustrations, to help explain the predictions.

· Use LeChatelier’s Principle to predict how changing the amount of water will affect the solution.

· Relate thermodynamic properties to LeChatelier’s principle and the solubility of salts.

1. Review your results for how many Strontium and Phosphate ions can be dissolved in 1x10-16liters of water. Predict what would happen if you started with 1x10-16liters of water and shook in 150 Strontium and 100 Phosphate.

a. Write down your prediction. Test it and explain your results. In your explanations, be sure to discuss which components of the solution represent reactants and which represent products. For this example, which direction does this equilibrium shift when you add these many ions (towards the products or reactants)?

b. Calculate the value of Q for 150 Strontium and 100 Phosphate; show your work. (See http://www.chem.purdue.edu/gchelp/howtosolveit/Equilibrium/Reaction_Quotient.htm for sample calculations)

c. Write the Ksp for 150 Strontium and 100 Phosphate (See Solubility Equilibrium for examples)

d. Summarize how comparing the values for Q and Ksp can help predict what will happen when you put salts in water. Illustrate your summary with “test tube” size drawings and “close-up” views to show the ions and crystals.

2. Write LeChatelier’s Principle in your own words. (Review LeChatelier Principle for examples and definitions)

a. If you had a saturated solution, what should happen if you add water? Explain your reasoning using LeChatelier’s Principle and then test your ideas using the simulation.

b. Predict how your answer would change for an unsaturated solution and then test your ideas.

c. Test to see how letting out water affect saturated and unsaturated solutions.

d. Explain using LeChatelier’s Principle what happens to saturated and unsaturated solutions when the amount of water is varied. How does temperature affect equilibrium of a solution? In your discussion, explain the directional shifts that result when a reaction is endothermic versus exothermic and relate these shifts in equilibrium to the salts in your simulations.