Solution Basics
What term describes a uniform mixture of substances that doesn’t separate over time?
Homogeneous
Which saying describes which solutes dissolve in which solvents?
"Like dissolves like"
What do you call liquids that completely mix in any proportion?
Miscible
Do colligative properties depend on solute identity or number of particles?
Number of particles (not identity)
If a solution contains 2 moles of solute and 8 moles of solvent, what is the solute’s mole fraction?
0.2 (2 ÷ (2+8))
Which type of mixture can appear clear even though it has multiple components?
Solution (homogeneous mixture)
A polar solute is added to a nonpolar solvent. Will it dissolve? Why or why not?
No; nonpolar solvent cannot dissolve polar solute
Liquids that do not mix form what?
Name a colligative property.
Freezing point depression, boiling point elevation, vapor pressure lowering, or osmotic pressure
Calculate the molality if 10 g of solute is dissolved in 100 g of water (assume molar mass = 100 g/mol).
1.0 m (0.1 mol ÷ 0.1 kg water)
BONUS! Before teaching, Mrs. Shepherd considered a career in this field.
What is geology?
Name one factor that can increase the solubility of a solid in a liquid.
Temperature (higher temp usually increases solubility for solids)
How can you determine if two liquids are miscible without mixing large amounts?
Mix a small drop of one in the other and observe if it spreads evenly
How does adding a solute affect the freezing point of a solvent?
It lowers the freezing point (freezing point depression)
You dissolve 15 g NaCl in 250 g water. Calculate molality.
1.03 m (15 g ÷ 58.44 g/mol ÷ 0.250 kg H₂O)
What are the two parts of a solution, and how can you differentiate them?
Solute (what is dissolved) and solvent (what does the dissolving); the solute is usually present in smaller quantity (or is the one that changes state)
How does pressure affect the solubility of gases in liquids?
Increasing pressure increases gas solubility
Why do immiscible liquids form separate layers instead of mixing?
Their molecules have very different intermolecular forces
How does adding a solute affect the boiling point of a solvent?
It raises the boiling point (boiling point elevation)
You dissolve 10 g NaOH (40 g/mol) in 500 mL water. Calculate the molarity.
0.5 M (0.25 mol ÷ 0.5 L)
A mixture separates into layers over time. Is this a solution? Why or why not?
No; solutions are homogeneous and do not separate into layers
Why do nonpolar solutes dissolve best in nonpolar solvents?
Because similar intermolecular forces allow solute and solvent particles to mix
If two miscible liquids are mixed, does heating always change the mixture? Explain.
No; miscible liquids mix in all proportions without needing heat
BONUS: What is the breed of Mrs. Shepherd's dog (bonus bonus if you know her name)
Great Pyrenees/German Shepherd mix
Nala
You dissolve 25 g of KBr (molar mass = 119 g/mol) in 200 g of water. What is the molality of the solution?
1.05 m