solutions liquids: more ordered that gases due to stronger intermolecular forces more dense than...
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SolutionsLiquids: more ordered that gases due to stronger
intermolecular forces• more dense than gases, but less compressible• Diffuse, just like gases, but slower • Dissociation: separation of ions when ionic
compounds dissolve in water• Surface tension: force that pulls parts of a liquid’s
surface together, to decrease surface area • Solute: substance being dissolved when making a
solution• Solvent: substance that does the dissolving
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• Solution: homogeneous mixture of two or more substance.– Air, alcohol in water, copper/zinc alloy (brass)
• Aqueous solution: when water does the dissolving• Hydrate: A compound that has water in it• Anhydrous: when you take the water out of a compound • Soluble: capable of being dissolved
– increasing temperature, increases KE, so more soluble, this is why you heat something to dissolve it.
• Insoluble: unable to be dissolved• Increasing pressure of a gas can increase solubility, by
pushing the particles into solution (like CO2 in pop)
• Increase temperatures will lower solubility of gases.
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• Saturated solution: contains the maximum amount of dissolved solute
• Unsaturated solution: contains less solute than the max• Supersaturated solution: contains more solute than the
maximum– Must be heated to get the more solute to dissolve, but
then as cooled will crystallized– Borax crystal ornaments
• Immiscible: liquids that are not soluble in each other.• Like dissolves like.
– Nonpolar dissolves nonpolar.
– Polar dissolves polar and ionic
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• Suspensions: when a particle (solute) in a solvent are so big that they settle out unless the mixture is constantly stirred. (medication)– Gravity pulls them to the bottom of the container
• Colloids: when a particle (solute) is intermediate in size.– Between a solution and a suspension– Cannot be separated with a filter– Cause a mixture to look cloudy– Emulsions: mayonnaise (oil in water)– Light will scatter when passed through a colloid, this
is known as Tyndall Effect
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• Ionization: when a solvent is strong enough to break a solute into ions. – Water can break Hydrochloric acid apart into ions
– H2O(l) + HCl(g) HCl(aq) H+(aq) + Cl-(aq) H3O+(aq) + Cl-(aq)
– H3O+ is the hydronium ion
• Concentration: the amount of a solute in a given amount of a solvent or solution.
• ppm : parts per million = mg solute/ L of solution• ppb: parts per billion = g solute/ L of solution
Concentration of Solutions
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Concentration of Solutions• Molarity: number of moles of solute in one liter of solution
– Symbol is “M”– If you have 1 mole of NaOH (40g) dissolved in enough
solvent (water) to make 1 liter, you will have 1 M NaOH or one molar NaOH
– Molarity (M) = amount of solute (moles) volume of solution (L)
• Molality: number of moles of solute per kilogram of solvent– Symbol is “m”– If you have one-half a mole of NaOH (20g) dissolved in 1
Kg of water gives 0.5 m NaOH or one-half molal of NaOH– Molality (m) = moles solute
mass of solvent (Kg) – Used in freezing point depression
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Colligative Properties• Properties that depend on the concentration of solute,
i.e. the number of particles (NaCl vs. C6H12O6)
• Adding more non-volatile solute will raise the boiling point and lower the freezing point of the solvent.
• Boiling Point Elevation: since there is more solute, there is a lower percent of solvent, so less water (solvent) will move from liquid to gas and thus boil. It will then take longer to boil
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• Particles block the surface of the solution, making it harder for the solvent (g) to escape. More KE is required, so the temperature must increase
• The boiling point elevation of a solvent in a 1 molal solution is 0.51oC/m
• tb = iKbm – Kb is the boiling point elevation constant
• (+.51°C/molal for water)
– m is molality– i is the number of particles
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• EX: What is the boiling point elevation when 150.0 grams of sucrose is added to 850. grams of water?
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• Freezing Point Lowering/Depression: adding more solute will decrease the percent of solvent (water) so it will decrease faster and at lower temperatures.
• When 1 mol of a nonelectrolyte solute is dissolved in 1 kg of water, the freezing point of the solution is –1.86oC, instead of 0oC for pure water.
• Freezing point depression, tf, is the difference between the freezing point of pure solvent and a solution of a nonelectrolyte in that solvent.
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• Solute particles interfere with the organization of the solid. In order to form the solid around the solute particles, the kinetic energy must decrease, so the freezing point is lowered
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Calculation for tf
• tf = iKfm
• Kf = the freezing point constant for a solvent
• i = the moles of ions (the number of particles)
• m = molality
• Kf(H2O) = -1.86oC/molal
• Ex: What is the freezing-point depression of water in a solution of 17.1 grams of Al2(SO4)3 in 200g of water? What would be the boiling-point elevation?
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Dilution:• When you dilute a solution the moles
remain the same, you are just adding water
• The concentration will change when you dilute solutions.
• moles of solution 1 = moles solution 2• So……, since M = mol/L and mol = MV
• For Dilution: – M1V1 = M2V2
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Stoichiometry of Solutions• How many ml of 3.0 M NaOH are needed to
neutralize 5.0 grams of acetic acid found in a vinegar solution? What is the M of the vinegar?
• How many grams of Mg can be dissolved by 15.0 ml of 6.0 M HCl? How much gas will be produced by this reaction at STP?
• 5.0 ml of 6.0 M HCl reacts with 25.0 ml .10 M NaOH. How much water will be produced?
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Electrolyte: A solution or substance in solution consisting of various chemicals that can carry electric charges.
• Strong Electrolyte: Solutions conduct electricity well. – Ionizes completely: contains many ions because of
complete dissociation. (HCl)
– NaCl (s) Na+ (aq) + Cl- (aq)
Na+
Na+
Na+
Cl-
Cl-
Cl-
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• Non-Electrolytes: Solutions do not conduct electricity• Does not ionize: substance exists as dissolved
molecules in solution. Like sugar.
• Weak Electrolytes: Solutions conducts poorly– Partially ionized: solution contains only a few
ions.– Appears that only some of the substance has
dissociated or ionized. Equilibrium!! – CH3COOH (aq) CH3COO- (aq) + H+ (aq)
CH3COO-H+
CH3COOH
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Acids and Bases• H+ or H3O+ usually indicates an acid
– Always add acid to water, not water to acid!
• OH- indicates a base
• Amphoteric: a substance that can act as either an acid or a base. – Solvents, such as water, that can both donate and
accept protons are usually described as amphiprotic
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Properties of Acids• Taste sour• Conducts an electrical current & Form H+ (aq)
• Turns indicators colors (blue litmus red & phenolphthalein colorless)
• Acids lose acidity when combined with bases, to form water and salts
• Corrosive to skin, react with water molecules in tissues. • Either produce a H+ ion or has H+ in it to donate• Basically it has a H in front of the compound • H2SO4(aq) + H2O(l) H+(aq) + HSO4
- (aq) acid base acid base
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Remember Naming of Acids
Binary Acids: HCl, HF, HI, HBr• hydro is the prefix, then the root name + -ic ending,
then the word acid
Oxyacids: hydrogen bonds with a polyatomic ion
• HNO2, H2SO4, HClO, HClO4, H2CO3 , etc.
• polyatomic name first, then replace -ate with -ic and replace -ite with -ous, then the word acid
Protic: hydrogen ions. (mono, di, tri)
monoprotic: an acid containing one ionizable hydrogen atom per molecule.
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Properties of Bases• Tastes bitter (like soap)• Conducts electricity & Forms OH- (aq) • Turns indicators colors (litmus blue & phenolphthalein pink)
• Neutralizes acids H+ (aq) + OH- (aq) --> H2O• Alkalies/ Bases become less alkaline when they are
combined with acids.• Feels slippery, turns oil in skin to soap• Corrosive to skin• Either has a OH- ion in it or produces a OH- ion
• NH3(g) + H2O(l) NH4+(aq) + OH-(aq)
base acid conj. acid conj. Base• Sodium Bicarbonate
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Acids and Bases• Arrhenius Acid: produces H+ ions, in aqueous solution
– H+ and H3O+ are the same thing, H can’t really lose its only e-– HCl(g) + H2O(l) H3O+ (aq) + Cl- (aq)
• Arrhenius Base: produces OH- ions, in aqueous solution– referred to as alkaline– KOH(s) + H2O(l) K+(aq) + OH-(aq)
• B.L. Acid: molecule or ion that is a proton donor– a proton is H+ – HCl + NH3 NH4
+ + Cl-
• B.L. Base: molecule or ion that is a proton acceptor – H2O + NH3 NH4
+ + OH-
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• Type Acid BaseArrhenius: H+ producer OH- producer|B.L.: H+ donor H+ acceptorLewis: electron-par acceptor electron pair donor
• Conjugate base: stuff left over after a B.L. acid has given up a proton
• Conjugate acid: stuff left over after a B.L. base has accepted a proton
• H2SO4(aq) + H2O(l) H3O+(aq) + HSO4- (aq)
acid base conj. acid conj. base• NH3(g) + H2O(l) NH4
+(aq) + OH-(aq) base acid conj. acid conj. base
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Strength of Acids and Bases• Acids and Bases are considered strong if they completely
ionize to form strong electrolytes
• Strong Acids: HCl, HNO3, H2SO4, HBr, HI, HClO4
– they easily lose their hydrogen ion (ionize completely)
• Weak Acids: HF, HC2H3O2 (CH3COOH)
– They want to keep their hydrogen until someone wants it more than them (partially ionize, so equilibrium)
• Strong Bases: those that are made up of hydroxide and group 1 or 2 metal.
• Weak Bases: substances that do not contain hydroxide, but rather generate hydroxide ions when reacting with water (like ammonia)
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• Strong acids and bases can be present in low concentrations
• To measure concentration of a solution of an acid we use Molarity, looking at the amount of H+ in a given volume.
• To measure strength of an acid we use pH, which measures the amount of H+ ions.
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pH and pOHA neutral solution has a pH of 7. pH scale : ranges from 0 to 14, where 7 is neutral.
The lower the number, the more acidic (0 - 6) The higher the number, the more basic (8-14)
pH: the measure of aciditypOH: the measure of alkalinity or how basic it ispH + pOH = 14
pH = -log[H3O+]pOH = -log[OH-]
In neutral solution [H3O+] = 1.0 x 10-7 In neutral solution [OH-] = 1.0 x 10-7
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pH
• Ex: [H+] = 1.8 x 10-5
pH = -log[1.8 x 10-5]pH = -(-4.74) pH = 4.74
• pH of 4 could be a lowconcentration of a strong acidor a high concentration of a weak acid.
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• Ex# 2: If the pH of Coke is 3.12, what is concentration of Hydrogen ion?
pH = - log [H+]
- pH = log [H+]
(Take antilog (10x) of both sides and get)
10 - pH = 10 log [H+]
10-pH = [H+]
[H+] = 10-3.12 = 7.6 x 10-4 M
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• Acid-base indicators are compounds whose colors are sensitive to pH. (like phenolphthalein)
• Indicators colors change in the presence of and acid or base depending on the indicator
• Some indicators change color at low pH and some at high pH
• Neutralization occurs when [H+] = [OH-]
Indicators
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Phenolphthalein
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Litmus Paper
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Acid-Base Neutralization
HX + MOH H2O + MX acid base water salt
If the moles of H+ = moles of OH- the acid and base have been neutralized. This is called the equivalence point and water and a salt is produced
Molarity = moles/liter
(Molarity) x (liters) = moles
(Molarity acid) x (volume acid) = (Molarity base) x (volume base)
MaVa = MbVb
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• Titration: add just enough of one solution to another (of known volume and concentration), so that they are equal in moles. – Very precise: use a buret to measure specific volume– Used to determine the equivalent volumes of acidic
and basic solution. • Equivalence point: point where two solutions are
present in equal amount. • End point: point where the indicator changes color
– Phenolphthalein turns pink at end point– Methyl red turn from red to yellow at the end point
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Ionization
• Water can auto-ionize– Meaning it will automatically turn into
hydronium (H3O+) and hydroxide ions (OH-)
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Of Water: • In neutral solution [H3O+] = [OH-]
• Kw = [H3O+][OH-] = 1 x 10-14
• At equilibrium of an acid & base the pH = 7 & [H3O+] = 1 x 10-7 and [OH-] = 1 x 10-7
• So Kw = [1 x 10-7][1 x 10-7] = 1 x 10-14
Equilibrium Ionization Constants
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Ex #1: What is the pH of the 0.0010 M Sr(OH)2 soln?
[OH-] = 2 x 0.0010 = 0.0020 (or 2.0 X 10-3 M)
pOH = - log 0.0020
pOH = 5.7
pH = 14 – 5.7 = 8.3
OR since, Kw = [H3O+] [OH-]
1 x 10-14 = [H3O+] (2.0 x 10-3 M)
1 x 10-14 = [H3O+] (2.0 x 10-3 M)
(2.0 x 10-3 M) (2.0 x 10-3 M)
[H3O+] = 0.5 x 10-11 M = 5.0 x 10-12 M
pH = - log (5.0 x 10-12) = 11.3
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Of Acids: • Only for weak acids, because only weak acids
partially ionize and are at equilibrium• Because the molar concentration of water is
constant, you leave it out of expression
• Weak acid has Ka < 1
• HA (aq) + H2O (l) H3O+ (aq) + A- (aq)
– Ka = [H3O+]x[A-]y
[HA]n
• CH3COOH + H2O H3O+ + CH3COO- what is Ka?
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Of Bases: • Only for weak bases, because only weak bases
partially ionize and are at equilibrium• Because the molar concentration of water is
constant, you leave it out of expression
• Weak base has Kb < 1
• B(aq) + H2O (l) BH+ (aq) + OH- (aq)
– Kb = [BH+]x[OH-]y
[B]n
• NH3 + H2O NH4+ + OH- , what is Kb?
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