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Chemistry Content

Describe solution formation using conventional terminology

Perform calculations for preparing solutions

Molarity


Dilute stock solution XXX
Determining mass solute
Determine mass hydrated solute XXX
Dilution, multiple solutes


Mole fraction
Percent by mass

Calculate stoichiometric quantities for reactions in solution

Integration with Other Sciences

Limestone caves

Integration with Mathematics

Proportionality

Existing Resources

Laboratory activities XXX

Calculator Probes Lesson

Phase changes with CBL

Calculator Lesson

Determine the relationship between vapor pressure and boiling

Laboratory Simulation

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At-Home Laboratory

Swimming pool kits
Environment kits
Soil test kits

Industrial Connection

Water treatment plants

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Diluting Stock Solutions

Dilute solutions often are prepared from more concentrated 'stock' solutions. A volume of the concentrated solution is measured, added to some solvent, and the resulting mixture diluted to a final volume by adding more solvent.

Weighing Hydrated (Solvated) Solids

Sometimes solutions are prepared by weighing solutes that contain some weakly bonded solvent. Copper sulfate pentahydrate, CuSO₄•5H₂O, ais a good example. The 'trick' when using these solutes is to remember that the mass measured includes some solvent. Therefore, when weighing, the mass of the hydrate is used -- and not just the formula mass of the anhydrous (dry, not solvated) solute.

Example:

Find the mass in grams of CuSO₄•5H₂O required to make 1500 mL of 0.20 M solution.

Mass CuSO₄•5H₂O = 1500 mL x 1 L/1000 mL x 0.20 mol/L x 249.686 g/mol = 74.9058 g CuSO₄•5H₂O. To the correct number of significant figures, 75 g.

Laboratory Activities

The following laboratory activities are available when teaching about water and solutions. DoChem 021, Stoichiometric Double Check, uses reaction in which it is possible to determine the masses of several reactants and products is conducted. A gaseous product is determined by mass lost from solution. One reactant mass and one product mass are determined directly. DoChem 60, Molar Concentration, allows measured volumes of acid solution to react with insoluble substances (CaCO₃, Zn). By measuring the mass of insoluble material dissolved as the result of reaction, the number of moles of acid is determined. From the moles and volume of acid, the molar concentration is determined. DoChem 071 involves a SmallScale experiment in which the combining ratios of solutions are used to determine formulas of compounds.

Demonstrations

DoChem 041, uses models containing magnets constructed from ordinary materials. The magnetic interactions cause different models to become "sticky," and thereby permit the illustration of hydrogen bonding and dipoles forces.