Standard 6: Solutions chapter 16 Chemistry Ms. Siddall

vocabulary 8. Saturated solution Aqueous solution 9. Unsaturated solution 10. Miscible 11. Immiscible 12. Concentration 13. Dilute solution 14. Concentrated solution 15. Molarity Aqueous solution Solvent Solute Solvation Electrolyte Solubility Solution

Standard 6a: solution definitions Solution: a homogeneous mixture of 2 or more substances in the same physical state. Properties: Particles are small Particles are evenly mixed Particles will not separate Examples: air (nitrogen & oxygen) Gatorade (water, sugar, etc) NaCl(aq) (salt & water)

Summary 1 Is muddy water a solution? Why/why not?

Solute: substance that is dissolved e.x. sugar Solvent: does the dissolving e.x. water Concentration: The amount of solute in a given amount of solvent e.x. [HCl] (aq) = aqueous = A solution where water is the solvent

Summary 2 Consider lemonade. What is the solvent? What are the solutes?

Standard 6b: Dissolving Process + + Solvent: H2O molecules with dipole Solute: Ionic crystal lattice -

Water molecules move away (diffusion) so the process is repeated Polar H2O molecules surround positive and negative ions and break apart crystal lattice Water molecules move away (diffusion) so the process is repeated Show animation

Summary 3 Explain how water dissolves ionic compounds

It takes energy to break bonds Energy needed to overcome lattice energy NaCl(s) Energy released during dissolving energy NaCl(aq) Dissolving

Summary 4 Does the energy diagram for dissolving NaCl represent an endothermic or exothermic process? Explain your answer.

Saturated solution: A solvent can not dissolve any more solute A saturated solution is at equilibrium. Particles are dissolving and precipitating at the same rate NaCl(s)  Na+(aq) + Cl-(aq)

Summary 5 Does the dissolving process stop at equilibrium? Explain why/why not.

Standard 6c: Factors that affect the dissolving process Some factors affect solubility (how much solute is dissolved) Some factors affect rate (how fast solute is dissolved) Some factors affect rate and solubility

Standard 6c: Factors that affect the dissolving process Factors affecting how much solute is dissolved 1. Type of solvent / solute Polar solvents dissolve polar & ionic solutes Non-polar solvents dissolve non-polar & covalent solutes e.x oil and water do not mix

Summary 6 Is oil a polar compound or a non polar compound? How do you know?

2. Temperature For solids: Temperature  solubility  Temperature increases kinetic energy of solvent particles therefore more solute can be dissolved For gases: Temperature  solubility  Temperature increases the kinetic energy of solute particles therefore more particles escape from solution

Summary 7 Why does the solubility of gas in solution decrease with increasing temperature?

3. Pressure (Gasses Only!) Increasing pressure forces more gas into solution Pressure  solubility  Pressure  solubility  low pressure High pressure Gas air solution

Summary 8 Does the concentration of carbon dioxide in your soda increase or decrease when you open the bottle? Why?

Factors that affect the rate of solubility (how quickly something dissolves) 1. Temperature: T rate T rate Increasing temperature increases kinetic energy = increased motion = increased diffusion

2. Surface Area (particle size): S.A.  (particle size ) rate  S.A.  (particle size ) rate  Increasing surface area increases opportunity for interaction between solute and solvent

3. Stirring: stirring  rate  stirring rate  Stirring increases particle motion so more particles can be dissolved at the surface of the solid

Summary 9 Name one factor that affects only solubility Name one factor that affects only rate Name one factor that affects rate and solubility

Standard 6d: calculations Molarity (mol/L) Molarity = Moles solute Liters solution Grams per Liter (g/L) = Grams solute Liters solution Percent Composition (%) grams solute x 100% grams solution Parts Per Million (ppm) grams solute x 106 grams solution