Solutions and Colloids Chemistry B11 Chapter 7 Solutions and Colloids

Mixtures Mixture: is a combination of two or more pure substances. Homogeneous: uniform and throughout Air, Salt in water Solution Heterogeneous: nonuniform Soup, Milk, Blood

Solutions Gas in gas (air) solid in solid (alloys) liquid in liquid (alcohol in water) Gas in liquid (cokes) solid in liquid (sugar in water) Solutions Well-mixed (uniform) – single phase homogenous transparent cannot be separated by filtration cannot be separated on standing sugar in water

Solutions (liquid in liquid) Solvent: greater quantity (water) Solute: smaller quantity (sugar) for liquid in liquid Immiscible: two liquids do not mix. miscible: two liquids can mix. alcohol in water (in any quantities)

Solutions Saturated: solvent contains or holds all the solute it can (at a given T). maximum solute that solvent can hold (Equilibrium). Unsaturated: solvent can hold more solute (at a given T). Is not the maximum solute that solvent can hold. Supersaturated: solvent holds more solute that it can normally hold (at a given T). (more than an equilibrium condition)

Temperature and Solutions Solubility: the maximum solute that will dissolve in a given amount of a solvent (at a given T). T  Solubility  T  Crystal is formed

Temperature and Solutions Solubility  Supersaturated solution Seeding A surface on which to begin crystallizing.

gas in liquid: T ↑ Solubility ↓ Global Warming

Pressure and Solutions Henry’s law P  Solubility  (gas in liquid) More pressure more interactions with the liquid

Concentration Concentration: amount of a solute dissolved in a given quantity of solvent. 1. Percent concentration: Weight solute (g) Weight / volume (W / V)% = × 100 Volume of solution (mL) Weight solute (g) Weight / Weight (W / W)% = × 100 Weight of solution(g) Volume solute (mL) Volume / volume (V / V)% = × 100 Volume of solution (mL)

Concentration 2. Molarity (M): number of moles solute dissolved in 1 L of solution. moles solute (n) Molarity (M) = volume of solution (L) Molarity × V = number of moles (n) prepare the solution: M, V → n (mol) → m (g)

prepare the solution: M, V → n (mol) → m (g) Preparing a solution prepare the solution: M, V → n (mol) → m (g) m (g) Volumetric flask

Concentration 3. Parts per Million (ppm): g solute ppm = × 106 g solvent Parts per billion (ppb): g solute ppb = × 109 g solvent

Concentrated solution Dilution Concentrated solution (Stock solution) Dilute solution

Dilution M1V1 = moles(n) before dilution M2V2 = moles(n) after dilution M1V1 = M2V2 M1V1/V2 = M2

# of Equivalents in 1 mole Number of Equivalents (Eq) in 1 mole of each ion is number of charge on that ion. Ion Charge # of Equivalents in 1 mole Na+ 1+ 1 Eq Ca2+ 2+ 2 Eq Fe3+ 3+ 3 Eq Cl- 1- SO42- 2-

Equivalent Ex. 1: How many equivalents of CO32- are in 1 mole of Al2(CO3)3? The charge of CO32- is 2- → 1 mole Al2(CO3)3 has 6 Eq CO32-. Ex. 2: How many equivalents of Fe3+ are in 5 mole of Fe2O3? The charge of Fe3+ is 3+ → 1 mole Fe2O3 has 6 Eq. 5 moles: 5 × 6 = 30 Eq

Water in our body About 60% mass of our body. Most of the reactions occur in aqueous solution. Participates in many biochemical reactions. Transports reactants and products from one place in our body to another. 5. Eliminates the waste materials from cells and our body (urine).

Solvent and Solute polar dissolves polar like dissolves like Nonpolar dissolves nonpolar like dissolves like Ions Hydrated by H2O Hydration

Solvent and Solute All nitrates (NO3-) and acetate (CH3COO-) are soluble in water. Most chlorides (Cl-) and sulfates (SO42-) are soluble in water. (except AgCl, BaSO4, and …) Most carbonates (CO32-), phosphates (PO43-) and hydroxides (OH-) are insoluble in water. (except NaOH, LiOH, KOH, and NH4OH)

Electrolytes + - Electrolyte: conducts an electric current. bulb + - electrolyte Electrolyte: conducts an electric current. Cl- Na+ Ionization (Dissociation) NaCl → Na+ + Cl- strong electrolytes: molecules dissociate completely into ions (NaCl). weak electrolytes: molecules dissociate partially into ions (CH3COOH). nonelectrolytes: molecules do not dissociate into ions (DI water).

non transparent, non uniform, large particles, cloudy (milky) Colloids Solutions: diameter of the solute particles is under 1 nm (10-9) Colloids: diameter of the solute particles is between 1 to 1000 nm. non transparent, non uniform, large particles, cloudy (milky) but a stable system

Colloids Tyndall effect: You can see the pathway of the light passing through a colloid. (particles scatter light.) emulsion: a mixture of immiscible substances (liquid-liquid). (milk and mayonnaise)

suspension: system does not stay stable and settles (> 1000 nm). (sand in water)

Brownian motion Random motion of colloid particles. Dust Why do colloidal particles remain in solution and do not stick together? 1. Surrounding water molecules prevent colloidal molecules from touching and sticking together. 2. A charged colloidal particle encounters another particle of the same charge, they repel each other.

Freezing and boiling point If we dissolve a solute in a solvent: bp  fp  ΔT: change of bp or fp (T2 - T1) i: number of particles K: constant (depend on solute) – Kb Kf M: molarity ΔT = ikM NaCl  Na+ + Cl- i = 2 K2SO4  2K+ + SO42- i = 3 C2H6O (Ethanol) i = 1

Osmotic Pressure Semipermeable membrane osmotic pressure Higher concentration → Higher osmotic pressure

Osmotic Pressure Water flows from low concentration to high concentration.

Osmotic Pressure Osmolarity (osmol) = M × i M: molarity i: number of particles Osmolarity ↑ → Osmotic pressure ↑

Hemolysis Crenation Isotonic solution Hypotonic solution Hypertonic solution Equal Water in Water out Hemolysis Crenation

The most typical isotonic solutions 0.9% (m/v) NaCl 5% (m/v) Glucose 0.9 g NaCl/100 mL of solution 5 g glucose/100 mL of solution Higher than these numbers → Hypertonic solution Lower than these numbers → Hypotonic solution

Dialysis Dilute solution