Solutions and other Mixtures Ch 20.1
Mixture A A combination of more than one pure substances physically combined.
Two Types: Homogeneous Same throughout Heterogeneous Different throughout
Homogeneous Mixtures Solution: a homogeneous mixture of 2 substances uniformly spread throughout a medium. Most consist of a solid dissolved in a liquid Made from two parts
Solution Parts: Solvent: substance that dissolves a solute. Greater quantity (ex. water) Solute: substance that dissolves in a solution. Lesser quantity (ex. Salt, sugar)
Dissolving Process 1.Dissociation: The separation of solute ions away from the salt crystal (only ionic compound solutes) 2. Solvation: The attraction of solvent particles to solute particles. They will then surround the solute particles. (called hydration when water is the solvent)
Dissociation of ions
Solvation/hydration
Polarity Property of a molecule caused by an unsymmetrical charge distribution. Molecule has a (+) and (-)( ) end Water is very polar, and is considered the universal solvent Most solutions use water as the solvent Salts behave like a polar substances because they are electrolytes
Solvent-Solute Solute Combinations Like dissolves in like Polar solutes dissolves in polar solvents Nonpolar solutes dissolves in non polar solvents
Polar solvent will attract a polar solute
Nonpolar solute will not dissolve in polar solvent
Solid, liquid, and Gas Solutions All mixtures of gases are solutions Most metal alloys are solutions (a mixture made from two or more solids) Mixtures between two liquids are classified by their miscibility Miscible liquids dissolve and form solutions immiscible liquids won t t dissolve
Solutions Properties Particles dissolve, they don t t settle out. Light can pass through liquid solutions Homogeneous mixtures (uniform)
Solution Equilibrium Solution Equilibrium rate of dissociating ions equals the rate that the ions resurface on the salt crystal.
Solution Equilibrium Unsaturated- A solution holding less solute than the solution can dissolve. Saturated Solution- A solution dissolving the maximum amount of solute particles. (in equilibrium) Supersaturated- An unstable solution containing more solute than the saturation point. Heat up a solution and dissolve more solute Then slowly bring down to a cooler temperature
When you add more solute particles, the whole solution will precipitate out and solidify.
Solubility Measures the amount of solute that will dissolve in a given amount of solvent at specific temperatures Saturated amount
Solubility Enthalpy (heat) of Solution ( H( sol ) Energy transfer during the dissolving process. Most solids become more soluble with rising temps. Positive H sol (endothermic) Gases become more soluble with colder temperatures. Negative H sol (exothermic)
Negative Hsol (exothermic) Positive Hsol (endothermic)
Dissolving Effects 1. Increase Surface Area- making more solute particles exposed to the solvent. Breaking down into smaller pieces 2. Stirring- Increases surface area 3. Changing Temperature- heating makes solvent molecules move quicker (more kinetic energy) 4. Already dissolved solute particles will slow down other solute from dissolving. 5. Pressure affects how well gases stay dissolved. Gases stay dissolved at higher pressures. (no affect on solid solute)
Carbonation bubbles form when the pressure is decreased when opening a soda bottle.
Precipitation Reactions Reaction between two solutions (double displacement) The ions in solution rearrange and interact with each other. The result will form an insoluble precipitate.
Precipitation Reactions AgNO 3 aq + NaCl aq AgCl (s) + NaNO 3 aq
CONCENTRATION The quantity of solute dissolved in a given quantity of solution. Adding water (solvent) will dilute your concentration. (decreasing the concentration)
CONCENTRATION Molarity (M) is measurement of concentration. (Molar) Molarity is the number of moles of solute dissolved in one liter of solution. M= moles of solute liter of solution Units = M or mol/l
Molarity Example How many moles of solute are present in 1.5 L of 0.20 M NaCl solution? M = moles of NaCl 0.20mol/L = moles liter solution 1.5 L Moles = 0.30 moles of NaCl needed to dissolve
Molarity Example How many grams of Copper II chloride should be used to prepare 25.0 ml of a 0.40 M solution? M = moles of CuCl 2.40 mol/l = moles liter solution.0250 L Moles =.010 moles of CuCl 2 needed to dissolve Now convert moles to grams.010 moles x 134 grams CuCl 2 = 1.3 grams 1 mole CuCl 2
CONCENTRATION Percent Concentration is another measurement of concentration. % = (solute/solution) x 100
Changing Concentration Diluting Concentrations: M 1 V 1 =M 2 V 2 How much water is needed to dilute a 2.0 M solution of HCl with a volume of 120 ml, to a 0.50 molar solution? 2.0 M x 120 ml =.50M x V2 V2= 480 ml So 360 ml of water is needed
Heterogeneous Mixtures Two Types: 1. Suspension 2. Colloids Ch 20.2
Suspensions Heterogeneous mixture a mixture that looks uniform when shaken. Particles Settle out, because the two parts of mixture repel each other. Label says to need to shake or stir Ex. orange juice with pulp, salad dressing
Colloid Intermediate between suspensions and solutions a mixture of very tiny particles that are scattered/dispersed in another substance. Two parts present (you only see one) Particles do not settle out or dissolve 3 major types
1. Aerosols Liquids or solids particles scattered in a gas Ex. Fog, smoke, hair spray, insect spray
2. Foam Mixture where gases are scattered in a solid or liquid Ex. Whipped cream, shaving cream, gels
3. Emulsion (most common) a mixture where a liquid is scattered through out another liquid or solid Usually homogenized (one phase) Contain emulsifying agent Substance with polar and nonpolar end Ex. Soap, detergent, egg Ex. mayonnaise, cheese, glue
LETS COMPARE Solutions Don t t Settle out (dissolve) Homogeneous (parts both polar or both nonpolar) Doesn t t Scatter Light (transparent) Colloids (emulsion) Don t t Settle out Don t t dissolve Intermediate between solutions and suspensions (polar and nonpolar end) Does Scatter Light (opaque) (Tyndall Effect occurs) Suspension Do Settle out and can be filtered Heterogeneous (one part polar and one part nonpolar) Can see two phases (Tyndall Effect occurs when shaken) Affected by colligative properties Not affected by colligative properties Not affected by colligative properties
Colligative Properties Ch 21.1
Colligative Properties The properties of solutions that are affected by the amount of solute added to solution. These properties are different than those of the pure solvent. Four Properties
1. Vapor Pressure The presence of nonvolatile solute at a specific concentration, lowers the vapor pressure of a solution. Solute particles are decreasing the opportunity for solvent particles to evaporate lowering the vapor pressure. This property allows scientist to separate the parts petroleum by distillation.
2. Boiling Point Elevation The presence of nonvolatile solute particles raises the boiling point. Adding salt to boiling water prevents you from over cooking the pasta.
3. Freezing Point Depression The presence of nonvolatile solute particles lowers the freezing point. Calcium chloride is added to streets and sidewalks to deice. Sodium chloride is added to ice to maintain lower temperatures while freezing homemade
Ch21.2 4. Osmosis The diffusion of solvent through a membrane from an area of higher solvent concentration to lower concentration. Semipermeable Membrane- barrier allowing solvent through, but block larger solute particles.
High concentration
4. Osmosis Osmotic Pressure- Pressure developed across a membrane that allows the diffusion of solvent particles to reach equilibrium. Chemistry behind your kidneys and making pickles
Ch23.1 Electrolytes Acids, bases, and salts when dissolved in water, will conduct electricity. Substances will ionize (acids) or dissociate (bases, salts)
Arrhenius Theory Acid aqueous solutions release hydrogen ions (H + ) Base aqueous solutions release hydroxide ions (OH - ) HCl H + + Cl - NaOH Na + + OH - Definition was too narrow
Hydronium Ion An ion formed when a free H + forms with water to form an H 3 O + Hydrated proton Hydrogen ions will not stay free for long and will bond with water molecules in solution
Brønsted nsted-lowry Theory In a chemical reaction, any substance that donates a proton (hydrogen ion) is an acid,, and any substance that accepts a proton (hydrogen ion) is a base. Acid + base conjugate acid + conjugate base Acid forms into CB Base forms into CA
Brønsted nsted-lowry Theory Conjugate acid the particle or substance obtained after a base has gained a proton (hydrogen) Conjugate base the particle or substance obtained after an acid has donated a proton (hydrogen) HCl + H 2 O H 3 O + + Cl - acid base C.A. C.B.
You Practice NH 3 + H 2 O NH 4+ + OH - base acid C.A. C.B. HNO 3 + NaOH H 2 O + NaNO 3 acid base C.A. C.B. NaHCO 3 + HCl NaCl + H 2 CO 3 base acid C.B. C.A.
Acid Properties Sour taste fruits (citric acid) Vinegar (acetic acid) Will burn if not diluted Neutralize bases Nonmetals will form acids with hydrogen ex HCl, H 2 SO 4
OUCH! Don t pick your scabs
Base Properties Bitter taste Slippery feel Household cleaners Also dangerous if not diluted Neutralize acids Also known as alkaline solutions Metals reacting with hydroxide will form bases ex NaOH, KOH, Ba(OH) 2
Naming Acids Binary contain two elements Step 1 add prefix hydro- Step 2 add stem element- Step 3 add -ic ending and the word acid EX. HCl is hydrochloric acid Name the following HF, H 3 P Write the formula of hydrosulfuric Acid
Naming Acids Ternary- contains three elements Step 1 identify polyatomic ion in formula Step 2 add appropriate suffix for ions that end in -ate add ic ending For ions that end in ite add -ous ending EX. H 2 SO 4 is sulfuric acid EX. H 2 SO 3 is sulfurous acid Name HNO 3 and HNO 2 Write the formula of phosphoric Acid
Naming Bases You already know how!!! Ex. NaOH = sodium Hydroxide Ex. Ba(OH) 2 = barium hydroxide
Amphoteric A A substance having the ability to act as an acid or a base Water is an example HCl (proton donor) + H 2 O (base) ---> > H 3 0 + + Cl - NH 3 (proton acceptor) + H 2 O (acid) ---> > NH + 4 + OH -
Acidic Anhydrides Acidic anhydride remove water Acid rain is an example Caused by the burning of fossil fuels. (producing NO x and SO 2 gases) NO x and SO 2 reacts with water vapor in atmosphere to form acids.
Acid Rain Precipitation that has an unusually high concentration of sulfuric and nitric acids resulting from pollution in air. Normal rain fall has ph of 5.3 due to natural carbonic acid forming in the atmosphere US cities average between 4-54
Strong Acids will completely ionize in water
Ch23.2 Neutralization Reactions You can neutralize a base with an acid or an acid with a base. The result will form water molecules and salts. NaOH + HCl NaCl + H 2 0
24.1 Measuring ph Acids the measure of the hydronium ion concentration and acidity range 0 14 00 acidic, 7 neutral, 14 basic
Very low ph
Very high ph Swimming anyone?
Measuring Acids Concentration read by powers of ten. Logarithms used to calculate. ph = -log [H 3 O + ] Concentration = 10 - ph If a substance has a H 3 O + concentration of 10-9 its ph is 9.
Measuring Acids poh the measure of the hydroxide ion concentration and how basic poh = -log [ OH - ] ph + poh = 14
Measuring Acids What is the ph of a sample with a hydronium concentration of 6.59 x 10-10 M? ph = -log [6.59 x 10-10 M] = 9.18 What is the hydronium concentration of a solution with a ph of 2.523? concentration = 10-2.523 = 3.00 x 10-3 M
Measuring Acids What is the ph of a solution with a hydroxide concentration of 2.93 x 10-2 M? poh = -log [2.93 x 10-2 M] = 1.53 ph = 14 1.53 = 12.47
Aquariums Scaled down models of natural ecosystems for different animals or plants. Much more sensitive to changes in temperature, ph, and any other substance that can get into the system. Buffers are used to stabilize the ph of the water system.
Indicator a compound that can reversibly change color depending on the concentration of H 3 O + ions. Used to measure ph Solution being tested must be colorless to see an accurate color change.
Process of finding the concentration of an unknown solution by neutralizing it with a standard solution. When the solution with an indicator changes color the end point of the neutralization reaction occurs. The concentration then can be calculated. Titration
Titration Example Problem What is the molarity of 125. 0 ml of HCl solution if it is neutralized by 160 ml of 5.00 M NaOH? HCl + NaOH NaCl + H 2 O moles = molarity x volume 5.00 M NaOH x 0.160 L NaOH = 0.800 moles NaOH Equal moles of HCl and NaOH are reacting, then 0.800 moles of HCl were also neutralized M = 0.800 moles HCl/ 0.125 L HCl= 6.4 M of HCl