Solutions Liquids: 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

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 CO 2 in pop) Increase temperatures will lower solubility of gases.

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

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

Ionization: when a solvent is strong enough to break a solute into ions. –Water can break Hydrochloric acid apart into ions –H 2 O(l) + HCl(g)  HCl(aq)  H + (aq) + Cl - (aq)  H 3 O + (aq) + Cl - (aq) –H 3 O + 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

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

Colligative Properties Properties that depend on the concentration of solute, i.e. the number of particles (NaCl vs. C 6 H 12 O 6 ) 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

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 0.51 o C/m  t b = iK b m –K b is the boiling point elevation constant (+.51°C/molal for water) –m is molality –i is the number of particles

EX: What is the boiling point elevation when grams of sucrose is added to 850. grams of water?

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 –1.86 o C, instead of 0 o C for pure water. Freezing point depression,  t f, is the difference between the freezing point of pure solvent and a solution of a nonelectrolyte in that solvent.

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

Calculation for  t f  t f = iK f m K f = the freezing point constant for a solvent i = the moles of ions (the number of particles) m = molality K f(H 2 O) = o C/molal Ex: What is the freezing-point depression of water in a solution of 17.1 grams of Al 2 (SO 4 ) 3 in 200g of water? What would be the boiling- point elevation?

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: –M 1 V 1 = M 2 V 2

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?

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+ Cl-

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!! –CH 3 COOH (aq) CH 3 COO - (aq) + H + (aq) CH 3 COO - H+ CH 3 COOH

Acids and Bases H + or H 3 O + 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

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 H 2 SO 4 (aq) + H 2 O(l) H + (aq) + HSO 4 - (aq) acid base acid base

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 HNO 2, H 2 SO 4, HClO, HClO 4, H 2 CO 3, 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.

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) --> H 2 O 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 NH 3 (g) + H 2 O(l) NH 4 + (aq) + OH - (aq) base acid conj. acid conj. Base Sodium Bicarbonate

Acids and Bases Arrhenius Acid: produces H + ions, in aqueous solution –H + and H 3 O + are the same thing, H can’t really lose its only e- –HCl(g) + H 2 O(l) H 3 O + (aq) + Cl - (aq) Arrhenius Base: produces OH - ions, in aqueous solution –referred to as alkaline –KOH(s) + H 2 O(l) K + (aq) + OH - (aq) B.L. Acid: molecule or ion that is a proton donor –a proton is H + –HCl + NH 3 NH Cl - B.L. Base: molecule or ion that is a proton acceptor –H 2 O + NH 3 NH OH -

Type Acid Base Arrhenius: H+ producer OH- producer| B.L.: H+ donor H+ acceptor Lewis: 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 H 2 SO 4 (aq) + H 2 O(l) H 3 O + (aq) + HSO 4 - (aq) acid base conj. acid conj. base NH 3 (g) + H 2 O(l) NH 4 + (aq) + OH - (aq) base acid conj. acid conj. base

Strength of Acids and Bases Acids and Bases are considered strong if they completely ionize to form strong electrolytes Strong Acids: HCl, HNO 3, H 2 SO 4, HBr, HI, HClO 4 –they easily lose their hydrogen ion (ionize completely) Weak Acids: HF, HC 2 H 3 O 2 (CH 3 COOH) –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)

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.

pH and pOH A 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 acidity pOH: the measure of alkalinity or how basic it is pH + pOH = 14 pH = -log[H 3 O + ] pOH = -log[OH - ] In neutral solution [H 3 O + ] = 1.0 x In neutral solution [OH - ] = 1.0 x 10 -7

pH Ex: [H+] = 1.8 x pH = -log[1.8 x ] pH = -(-4.74) pH = 4.74 pH of 4 could be a low concentration of a strong acid or a high concentration of a weak acid.

Ex# 2: If the pH of Coke is 3.12, what is concentration of Hydrogen ion? pH = - log [H + ] - pH = log [H + ] (Take antilog (10 x ) of both sides and get) 10 - pH = 10 log [H+] 10 -pH = [H + ] [H + ] = = 7.6 x M

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

Phenolphthalein

Litmus Paper

Acid-Base Neutralization HX + MOH H 2 O + 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) M a V a = M b V b

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

Ionization Water can auto-ionize –Meaning it will automatically turn into hydronium ( H 3 O + ) and hydroxide ions ( OH - )

Of Water: In neutral solution [H 3 O + ] = [OH - ] K w = [H 3 O + ][OH - ] = 1 x At equilibrium of an acid & base the pH = 7 & [H 3 O + ] = 1 x and [OH-] = 1 x So K w = [1 x ][1 x ] = 1 x Equilibrium Ionization Constants

Ex #1: What is the pH of the M Sr(OH) 2 soln? [OH-] = 2 x = (or 2.0 X M) pOH = - log pOH = 5.7 pH = 14 – 5.7 = 8.3 OR since, K w = [H 3 O + ] [OH - ] 1 x = [H 3 O + ] (2.0 x M) 1 x = [H 3 O + ] (2.0 x M) (2.0 x M) (2.0 x M) [H 3 O + ] = 0.5 x M = 5.0 x M pH = - log (5.0 x ) = 11.3

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 K a < 1 HA (aq) + H 2 O (l) H 3 O + (aq) + A - (aq) –K a = [H 3 O + ] x [A - ] y [HA] n CH 3 COOH + H 2 O H 3 O + + CH 3 COO - what is K a ?

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 K b < 1 B(aq) + H 2 O (l) BH + (aq) + OH - (aq) –K b = [BH + ] x [OH - ] y [B] n NH 3 + H 2 O NH OH -, what is K b ?