Topic 1 (Review) What does (aq) mean? -- dissolved in water. Solution: a homogeneous mixture; solutes dissolved in solvents

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Osborne Kristopher Hodges
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1 Solutions Unit 6

2 Topic 1 (Review) What does (aq) mean? -- dissolved in water. Solution: a homogeneous mixture; solutes dissolved in solvents Solute: dissolved particles in a solution (i.e. NaCl) Solvent: the dissolving medium in a solution (H 2 O) Saturated: a solution containing the maximum amount of solute for a given amount of solvent at a constant temperature and pressure.

3 Regents Review A compound differs from a mixture in that a compound always has a 1. homogeneous composition 2. maximum of two components 3. minimum of three components 4. heterogeneous composition Which substance cannot be decomposed into simpler substances? 1. ammonia 2. aluminum 3. methane 4. methanol

4 Solubility of Ionic Compounds Topic 2 Water! Cl - the water molecule has a negative and a positive end. H + H Which end of the water molecule do you think will be attracted to a cation in solution? O Which end of the water molecule do you think will be attracted to the anion in solution? - Na +

5 Water Molecules in Solution When certain IONIC COMPOUNDS (compounds made of two or more ions) are added to water, they will break apart, or DISSOCIATE. Examples: NaCl (s) Na + (aq) + Cl - (aq) CaCl 2(s) Ca +2 (aq) + 2Cl - (aq) AgNO 3 Be(NO 3 ) 2

6 Solubility Rules Use TABLE F Soluble: will dissolve in water to form an aqueous solution Insoluble: will NOT dissolve in water to form an aqueous solution. Table F Solubility Guidelines for Aqueous Solutions Ions That Form Soluble Compounds Group 1 ions (Li +, Na +, etc.) ammonium (NH 4 + ) nitrate (NO 3 ) acetate (C 2 H 3 O 2 or CH 3 COO ) hydrogen carbonate (HCO 3 ) chlorate (ClO 3 ) halides (Cl, Br, I ) Exceptions when combined with Ag +, Pb 2+, or Hg 2 2+ sulfates (SO 4 2 ) when combined with Ag +, Ca 2+, Sr 2+, Ba 2+, or Pb 2+ Ions That Form Insoluble Compounds* Exceptions carbonate (CO 3 2 ) when combined with Group 1 ions or ammonium (NH 4 + ) chromate (CrO 4 2 ) when combined with Group 1 ions, Ca 2+, Mg 2+, or ammonium (NH 4 + ) phosphate (PO 4 3 ) when combined with Group 1 ions or ammonium (NH 4 + ) sulfide (S 2 ) when combined with Group 1 ions or ammonium (NH 4 + ) hydroxide (OH ) when combined with Group 1 ions, Ca 2+, Ba 2+, Sr 2+, or ammonium (NH 4 + ) *compounds having very low solubility in H 2 O

7 Practice the Solubility Table / Rules! NaBr Soluble in water Fe(PO 4 ) NOT Soluble in water (NH 4 ) 2 S Soluble in water CaSO 4 NOT Soluble in water

8 Regents Practice A solution in which the crystallizing rate of the solute equals the dissolving rate of the solute must be 1. saturated 2. unsaturated 3. concentrated 4. dilute

9 Solution Concentration Topic 3 Which solution has the higher concentration? Explain how you know, in terms of particles.

Molarity - Concentration Defined Quantitative measurements of solution concentration: Molarity (M) % Composition by Mass Parts Per Million (ppm) Table T molarity = moles of solute

10 Molarity - Concentration Defined Quantitative measurements of solution concentration: Molarity (M) % Composition by Mass Parts Per Million (ppm) Table T molarity = moles of solute liter of solution Make sure volume is in LITERS (convert ml into L) If you are given grams, you will need to convert them to moles. Let s review this g CaCl 2 = moles CaCl 2

11 Molarity Calculations Practice What is the molarity of a solution in which 58 g of NaCl are dissolved in 2.0 L of solution? What is the molarity of a solution in which 2.5 moles of AgNO 3 is dissolved in 500 ml of solution?

12 More Molarity Practice How many grams of KNO 3 should be used to prepare 2.00 L of a M solution? To what volume should 5.0 g of KCl be diluted in order to prepare a 0.25 M solution?

13 Regents Practice A student wishes to prepare approximately 100 milliliters of an aqueous solution of 6M HCl using 12 M HCl. Which procedure is correct? 1. adding 50 ml of 12 M HCl to 50 ml of water while stirring the mixture steadily. 2. adding 50 ml of 12 M HCl to 50 ml of water and then stirring the mixture steadily. 3. adding 50 ml of water to 50 ml of 12 M HCl while stirring the mixture steadily. 4. adding 50 ml of water to 50 ml of 12 M HCl and then stirring the mixture steadily. Let s study this question a bit before we try to answer it... add acid to water or water to acid? Enthalpy of dissociation?

14 Electrolytes Topic 4 The Electric Pickle!! Make observations of the pickle. What is it soaking in? OBSERVATIONS Why do you think this happened?

15 What is an Electrolyte?...more than just Gatorade! electrolytes it must be able to dissolve in water! Forms ions in solution by dissociation (ionic = metal + nonmetal) CONDUCT ELECTRICITY An electrolyte is a substance that breaks into ions when dissolved in water and conducts electricity. Covalent compounds are never electrolytes; they do not dissociate into ions. When they dissolve, they stay together as molecules

16 ***Big Idea*** Conductivity 1. There must be CHARGED PARTICLES (ions are an example of a charged particle) 2. The charged particles must be ABLE TO MOVE FREELY (like in a water solution)

17 Categories of Electrolytes Categories of Electrolytes Electrolytes are classified according to the types of ions formed by the substance dissolves. lectrolytes are classified according to when the typeit of ions formed by the substance hen it dissolves. Svante Arrhenius was a Swedish chemist who first studied this Arrhenius Acid - athe substance that dissolves to form H+1 ranch of1. chemistry, and developed following categories: ion as the ONLY positive ion in solution.+1 (Look at Table 1. Arrhenius Acid a substance that dissolves to form H ion as the ONLY positivek.) ion in solution. (Look on Table K) vinegar contains acetic acid lemons contain vitamin C ascorbic acid 2. Arrhenius Base - a substance that dissolves to form (OH)-1 ion as the ONLY

18 Electrolyte Categories vinegar contains acetic lemons containtovitamin 2. Arrhenius Base -acid a substance that dissolves form C asc (OH)-1 ion as the ONLY negative ion in solution. (Look Arrhenius Base a substance that dissolves to form (OH) ion as on Table L.) negative ion in solution. (Look on Table L) Not that kind of base! Soap is a base 3. Salts a substance that dissolves to form a positive ion other than -1

19 Electrolyte Categories 3. Salts - a substance that dissolves to form a positive ion other than H +1 and a negative ion other than (OH) -1 Not this Salt!!

20 Examples of Electrolytes! Dissolving in water Type of Electrolyte Why? HCl (g) H +1 (aq) + Cl - (aq) NaOH (s) Na +1 (aq) + (OH) -1 (aq) K(NO 3 ) (s) K +1 (aq) + (NO 3 ) -1 (aq) acid base salt H +1 is the only positive ion in solution (OH) -1 is the only negative ion in solution Positive and negative ions other than H +1 and (OH) -1 are present

21 Regents Practice!!! Which formula represents a salt? 1. KOH 2. KCl 3. CH 3 OH 4. CH 3 COOH Which substance can be classified as an Arrhenius acid? 1. HCl 2. NaCl 3. LiOH 4. KOH

22 Properties of Acids & Bases (ph) Topic 5 Which of these common products are acids? Which are bases? How do you know?

23 Acid: Dissociate in water to form H +1 ions (H 3 O +1 or hydronium ion). Base: Dissociate in water to form OH -1 (hydroxide ion) There are different categories of acids and bases depending on how many H +1 or (OH) -1 ions are present in solution.

24 ph shows acidity or alkalinity of a solution; a ph of 7 is neutral, a ph of less than 7 is acidic, and a ph of greater than 7 is basic

If [H + ] is 1 x 10-12 M, ph = 12 1 5 Notice that as the [H + ]

25 IB: ph = -log[h + ] ph is a measure of the concentration of the H + If [H + ] is 1 x 10-1 M, ph = If [H + ] is 1 x 10-5 M, ph = If [H + ] is 1 x M, ph = Notice that as the [H + ] decreases, the ph increases (the solution becomes more basic)

26 Properties of Acids & Bases (ph) Indicators

28 Exponential Increases in Concentration H + OH As ph decreases by 1, the [H + ] concentration increases by 10 As ph decreases by 3, the [H + ] concentration increases by 1000

29 Regents Practice Which ph will turn methyl orange red?

30 Topic 6 - Neutralization and Titration Watch this YouTube video... (from :55 1:37)! It is a scrubber at a power plant talking about the process of removing particulates from the air (pollution).! Why would we want to pull particulate matter from the air?! What must the slurry be made of in order to help this process along?

31 Neutralization A neutralization reaction is a type of double replacement reaction. Salt and water are always formed. For example: Na(OH) + H(NO 3 ) Na(NO 3 ) + H(OH) base acid salt water Label these: H 2 SO NaOH 2 HOH + Na 2 (SO 4 ) acid base water salt

32 Neutralization When an acid reacts with a base, an ionic salt and water are formed. HCl + NaOH H 2 O + NaCl HBr + KOH H 2 O + KBr HNO 3 + NaOH H 2 O + NaNO 3 H 2 SO4 + 2 KOH 2 H 2 O + K 2 SO 4 ( note the equation is balanced) 2 HNO 3 + Mg(OH) 2 2 H 2 O + Mg(NO 3 ) 2 (note the equation is balanced) *A solution is neutral when the # of H 3 O + ions = the # of OH - ions

33 Neutralization Example Example: 2 HBr + 1 Mg(OH) 2 1 MgBr H 2 O Your Turn HNO 3 + KOH

34 Titration Online Tutorial Titration: controlled neutralization (can be seen by a color change) Determine unknown concentration **One unit of H 1+ is required to wipe out (neutralize) one unit of (OH) 1-.

35 Titrations In a neutral solution, the moles of H + = moles of OH # moles = Molarity x Volume (# moles = M V) Therefore, in a neutral solution: M A V A = M B V B Example: If 50.0 milliliters of 3.0 M HNO 3 completely neutralized ml of KOH, what was the molarity of the KOH solution?

36 Regents Practice Given the equation: H + + OH - H 2 O Which type of reaction does the equation represent? 1. esterification 2. decomposition 3. hydrolysis 4. neutralization When HCl(aq) is exactly neutralized by NaOH(aq), the hydrogen ion concentration in the resulting mixture is 1. always less than the concentration of the hydroxide ions 2. always greater than the concentration of the hydroxide ions 3. always equal than the concentration of the hydroxide ions 4. sometimes greater and sometimes less than the concentration of the hydroxide ions

ed. Brad Collins Aqueous Chemistry Chapter 5 Some images copyright The McGraw-Hill Companies, Inc. Sunday, August 18, 13

ed. Brad Collins Aqueous Chemistry Chapter 5 Some images copyright The McGraw-Hill Companies, Inc. A solution is a homogenous mixture of 2 or more substances at the molecular level The solute(s) is(are)