Solutions

What is a solution? A homogeneous mixture A homogeneous mixture Composed of a solute dissolved in a solvent Composed of a solute dissolved in a solvent Solute Solvent

How is a solution formed? Through the process of Through the process of Solute particles separate from each other and mix with the solvent Solute particles separate from each other and mix with the solventparticles Solvent particles Solvent particles surround the solute particles and pull them away from other solute particles solvation

Solute and Solvent Solvent Solvent Does the dissolving Does the dissolving Greater quantity (usually) Greater quantity (usually) Solute Solute What is dissolved What is dissolved Lesser quantity (usually) Lesser quantity (usually)

Like dissolves like Baking soda will dissolve in water, but not in oil…..why? Baking soda will dissolve in water, but not in oil…..why? “Like dissolves like” refers to the bonding and polarity of the particles in the solute and solvent “Like dissolves like” refers to the bonding and polarity of the particles in the solute and solvent Polar means a substance Polar means a substance has a positive and a negative end Ionic compounds Ionic compounds

Ionic compounds in solution Cl - Na + Cl - Na + Cl -

Solubility Only a certain amount of solute can dissolve in a solvent under a certain set of conditions Only a certain amount of solute can dissolve in a solvent under a certain set of conditions When too much solute is added to a solution at that temperature, the excess solute will crystallize When too much solute is added to a solution at that temperature, the excess solute will crystallize and fall out of solution Solubility is the maximum Solubility is the maximum amount of a solute that amount of a solute that dissolves in a solvent at a given temperature

Saturation A saturated solution A saturated solution contains the maximum amount of dissolved solute contains the maximum amount of dissolved solute for a given amount of solvent for a given amount of solvent at a specific temperature and pressure at a specific temperature and pressure

Supersaturation A supersaturated solution A supersaturated solution contains more dissolved solute than a saturated solution contains more dissolved solute than a saturated solution at the same temperature. at the same temperature.

Solubility Curves Shows how much solute will dissolve in 100 g of water at a certain temperature The line represents the saturated amount of solute Underneath the line represents an unsaturated amount Above the line represents a supersaturated amount

Which substance is most soluble at 40°C? How many grams of NH 4 Cl will dissolve at 50°C? What two substances have the same solubility at 24°C? If you place 70 grams of KBr into 100g of water at 60°C, what type of solution have you made? How many grams of NaNO 3 will dissolve in 300.0g of water at 10.0°C? NaNO 3 ~ 50 grams Yb 2 (SO 4 ) 3 3 KNO 3 unsaturated ~ 240 grams (80 x 3)

Increasing Solubility - Solids Increase the temperature Increase the temperature Why? Increases the amount of solute-solvent collisions and increases speed and energy of particles Why? Increases the amount of solute-solvent collisions and increases speed and energy of particles Agitate the solution (stir) Agitate the solution (stir) Why? Brings more Why? Brings more solvent particles closer to the solute Decrease the particle size Decrease the particle size Increases the surface area Increases the surface area of the solute, making it easier for solvent particles to surround the solute

Mixtures: 2 types Heterogeneous vs Homogeneous

Homogeneous Mixture A mixture where the components that make up the mixture are uniformly distributed throughout Examples: Solutions are homogeneous mixtures: such as ice tea, sugar dissolved in water; air is a solution of gases.

Colloids Particle size 1-100nm Scatter light (Tyndall Effect) Can be heterogeneous or homogeneous depending on particle size Examples include: milk, fog, gelatin

Heterogeneous Mixture A mixture where the components of the mixture are not uniform or have localized regions with different properties Ex. Salad, concrete, salad dressing, pepto bismol, OJ with pulp

Solutions, colloids, suspensions Solutions: particle size <1 nm; homogeneous mixture; ex: ice tea Colloids: particle size nm; scatter light (Tyndall Effect); can be both homogeneous or heterogeneous; ex; milk, fog, gelatin Suspensions; particle size >100nm; scatter light, heterogeneous: Ex: OJ, salad

Increasing Solubility – Gases Decrease the temperature Decrease the temperature Increase the pressure Increase the pressure If you increase the pressure, If you increase the pressure, think of pressing the gas particles into the liquid. Increasing pressure always Increasing pressure always increases the amount of gas that can be dissolved in a liquid.

Rate of Solvation Greater solubility = Faster solvation The same factors that increase solubility, increase the rate of solvation The same factors that increase solubility, increase the rate of solvation

Concentration The larger the ratio of solute to solvent becomes, the more concentrated the solution is. The larger the ratio of solute to solvent becomes, the more concentrated the solution is. Concentrated – large ratio of solute to solvent Concentrated – large ratio of solute to solvent Dilute – small ratio of solute to solvent Dilute – small ratio of solute to solvent

Rates of Reaction Concentration affects the rate of reaction Concentration affects the rate of reaction Concentrated solutions react faster than dilute solutions Concentrated solutions react faster than dilute solutions

Molarity Most commonly used in chemistry Most commonly used in chemistry Abbreviated as M Abbreviated as M Moles of solute in per liter of solution Moles of solute in per liter of solution moles of solute Liters of solution M =

Electrolytes Electrolyte – ionic compound whose aqueous solution conducts an electric current Electrolyte – ionic compound whose aqueous solution conducts an electric current – electrolyte – electrolyte – non-electrolyte – non-electrolyte NaCl Sugar How many moles of ions are produced by dissolving 1 mole of NaCl in water?

Colligative Properties Colligative - depending on the collection Colligative - depending on the collection Properties dependent on concentration, number of particles present Properties dependent on concentration, number of particles present

Boiling Point Elevation When vapor pressure equals atmospheric pressure, water boils When vapor pressure equals atmospheric pressure, water boils More particles = lower vapor pressure More particles = lower vapor pressure Lower vapor pressure = higher boiling point Lower vapor pressure = higher boiling point More particles = higher boiling point More particles = higher boiling point Which raises boiling point more, 1 mole of NaCl in water, or 1 mole of sugar in water?

Freezing Point Depression Solute particles interfere with attraction between solvent particles Solute particles interfere with attraction between solvent particles More particles = lower freezing point More particles = lower freezing point

Osmosis Osmosis – diffusion of solvent across a semi- permeable barrier Osmosis – diffusion of solvent across a semi- permeable barrier Solvent goes from: Solvent goes from: Area of more solvent → Area of less solvent Area of more solvent → Area of less solvent

Osmosis Semi-permeable barrier Pure Solvent Solution

Osmosis and Concentration Higher concentration = more osmotic pressure Higher concentration = more osmotic pressure

Osmosis and you

Colligative Properties Review Atmosphere Vapor Pressure

Miscible and Immiscible Substances that are miscible will dissolve in each other. Example: alcohol and water Substances that are immiscible will mix but immediately separate. Example: oil and vinegar