Solutions More Vocab Soluble Soluble capable of being
Solutions: More Vocab
Soluble: Soluble capable of being dissolved A substance that dissolves in another substance is said to be soluble in that substance
Insoluble A substance that does not dissolve in another substance
• Solubility: maximum amount substance that dissolves in given amount of another substance – LIMIT to amount solute that dissolves in given amount solvent – affected by temperature and pressure
• Rate of dissolving is different from amount that will dissolve! • Rate is how fast • Amount is how much
Factors that affect the rate of dissolving • temperature • stirring or agitation • amount of surface area of solute • amount of solute already dissolved
Dissolving • Dissolving is physical change [Reminder: all physical & chemical changes accompanied by change in energy]
source dissolved covalent substances: produce molecules in solution C 6 H 12 O 6(s) + H 2 O(l) C 6 H 12 O 6(aq)
dissolved ionic substances: produce ions in solution Na. Cl(s)+H 2 O(l) Na+1(aq) + Cl-1(aq)
Solvation • Interaction between solvent molecules & solute particles – solute particles surrounded by solvent particles during dissolving process • Solute particles may be: • ions • polar molecules • non-polar molecules • Solvent molecules may be: • polar • non-polar
Hydration describes solvent-solute interaction when solvent is water
Hydration of chloride ion Also called: molecule-ion interaction
Molecule-ion interaction Solute-solvent interaction must be greater than: interaction between solute particles for dissolving to occur
Solvation in different systems.
Solubility • amount solute dissolved in specific solvent at given TEMPERATURE and PRESSURE • units: grams solute per 100 grams solvent
Solubility Curves of Selected SOLIDS Solubility traces for most solids have (+)’ve slopes; The hotter the solvent, the more solute dissolves
Solubility Curves of Selected GASES Solubility traces for all gases have (–)’ve slopes Do you know why most fish prefer cold water?
Vocabulary Interlude • Miscible: Miscible two liquids that WILL MIX together in any amounts – Water and ethanol are miscible in all proportions • Immiscible: Immiscible liquids that will NOT MIX – Oil and water are immiscible
Oil & H 2 O are immiscible
Types of Solutions Matter Mixtures Pure Substances Elements Compounds Homogeneous Mixtures = Solutions Heterogeneous Mixtures Conduct current Nonconductor
Electricity • What do you need to conduct electricity? Mobile, positively charged particles!!!!
Vocabulary Interlude • Electrolyte: Electrolyte • substance that dissolves in water to form solution that conducts electricity • ions in solution • Nonelectrolyte: Nonelectrolyte • substance that dissolves in water to form solution that does not conduct electricity • neutral molecules in solution
Electrolyte vs. Nonelectrolyte Which solution conducts a current?
Dilute vs. Concentrated • Concentrated –large amounts of solute • Dilute –small amounts of solute
Which solution is most dilute? The most concentrated? How can you tell? The stronger the color, the more concentrated the solution
To dilute a Solution: add MORE solvent
Which solution is more concentrated? More dilute? What can you say about the # of solute particles in pictures b and c? the # is the same!
Unsaturated Solution Less than maximum amount solute that will dissolve at given T and P
Saturated Solution • No more solute will dissolve at given T&P • Solubility = amount solute required to form saturated solution
The solution is saturated when the solute stops dissolving
Dynamic Equilibrium in Saturated Solution Microscopic level: Rate dissolving = Rate recrystallization Macroscopic level: No apparent change
Supersaturated Solution • Contains more solute than saturated solution – VERY unstable – have to be clever to make these (need to use heat)
Testing for saturation: additional crystal of solute into solution and see what happens
3 possible results: • Crystal dissolves: Unsaturated solution • Crystal sinks to bottom of solution: Saturated solution Bam! Suddenly have lots of solid solute in beaker: • Supersaturated solution
What kind of solution was this?
How do terms saturated, unsaturated & supersaturated fit in with the solubility curves?
Saturated solns: • any point on trace line (max solute dissolved) Supersaturated solns: • all points above trace lines (more than max) Unsaturated solutions: • all points below trace lines (less than max)
A B Characterize points A, B, C, D with respect to KNO 3 trace line (dilute, concentrated, saturated, unsaturated, or supersaturated) A, C = concentrated & supersaturated C D B=concentrated & saturated D = dilute & unsaturated
Solubility Graphs • Traces: have positive or negative slopes • Most solids have positive slope – the hotter the water, the more solute dissolves – The colder the water, the less solute dissolves • All gases have negative slope – the hotter the water, the less gas dissolves – The colder the water, the more gas dissolves
Summary of Dissolving • Occurs at surface of solid • Interaction: between solute & solvent – Interaction called “solvation” – Interaction called “hydration” (if solvent is H 2 O) • Involves: change in energy
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