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CHEMISTRY REVIEW. Ionic Bonding Ionic compounds are formed when one or more valence electrons are transferred from a metal atom to a non-metal atom.

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Presentation on theme: "CHEMISTRY REVIEW. Ionic Bonding Ionic compounds are formed when one or more valence electrons are transferred from a metal atom to a non-metal atom."— Presentation transcript:


2 Ionic Bonding Ionic compounds are formed when one or more valence electrons are transferred from a metal atom to a non-metal atom.

3 General properties high Melting Point, Boiling point and hard. It takes a lot of energy to break the bonds between the ions. When ionic compounds are dissolved in water they dissociate into their ions. Conduct electricity when dissolved in water NaCl (s)  Na + (aq) + Cl - (aq)

4 Example – Ca bonds with O Step 1 CaO Step 2 2+2- CaO Step 3 2+2- CaO Step 4 Ca 2 O 2 = CaO The 2’s disappeared because we reduced to lowest terms.

5 IUPAC nomenclature is a system of naming chemical compounds. It is maintained by the International Union of Pure and Applied Chemistry.

6 Ionic Binary compounds A binary compound is one that only contains two elements in the compound. An ionic binary compound is a compound contains one metal and one non-metal.

7 Ionic Binary Compounds: IUPAC Naming Consists of two types of monoatomic ions 1. The metal ion is always written first and retains its whole name 2. The non-metal is written second and has a slight change, the ending (suffix) is changed to –ide Example: Na + Cl - use the cross over method NaCl IUPAC name: sodium chloride The metal name is written in full and the non-metal has the –ide­ suffix added to it. Sodium chloride

8 Binary compounds can be made up of more than two ions, provided that there are only two types of elements. Example: Al 2 O 3

9 Ionic Multivalent Binary Compounds A multivalent compound is one that may have varied numbers of electrons in its valence shell. This means that they can form compounds in various proportions. SnO 2  Sn 4+ O 2-  tin (IV) oxide SnO  Sn 2+ O 2-  tin (II) oxide

10 Polyatomic Ions  Polyatomic Ions are ions that are composed of more than one atom. The entire molecule carries a charge to it. Also Called Radicals (Bottom of Data Sheet) Ammonium, Acetate, Carbonate, Nitrate, hydroxide, Phosphate, Sulphate, Chlorate, Bromate, Iodate.

11 Polyatomic Ions Example- NO 3 - SO 4 2- PO 4 3-

12 Bonding Ionic Bonding with polyatomic ions occurs in the same manner as it does with binary atomic molecules. ( Use the crossover method) Examples.. NaOH = sodium hydroxide Cu(ClO 4 ) 2 = copper (II) perchlorate Tin (IV) chlorate = Sn (ClO 3 ) 4

13 Example Step 1 Na + NO 3 - Step 2 1+ 1- Na NO 3 Step 3 1+ 1- Na NO 3 Step 4 NaNO 3

14 Word Equations A word equation is a way of representing a chemical reaction: It tells you what reacts and what is produced. Examples: Silver nitrate + copper  silver + copper (II) nitrate Reactants Products Hydrogen + Oxygen  water vapour Reactants Products

15 The Conservation of Mass In a chemical reaction, the total mass of the reactants is always equal to the total mass of the products. This tells us a few things. Atoms do not change in a reaction. The molecules that they form can be changed but the atoms themselves are not. Mass cannot be destroyed. If it could we could use E = MC 2 to create energy

16 Skeleton equations + Balancing Equations Example: CH 4 + O 2  H 2 O + CO 2 The above equation does not demonstrate the Law of Conservation of Mass. The law states that the mass of the products will equal the mass of the reactants. This one does (it is balanced) CH 4 + 2 O 2  2 H 2 O + CO 2

17 Balancing We can’t change the formulas of the products or reactants so the only thing we can do is change the number of molecules instead of their formulas. CH 4 + O 2 + O 2  H 2 O +H 2 O + CO 2 = CH 4 + 2O 2  2H 2 O + CO 2 Now the chemical equation is balanced and the mass of the reactants will equal the mass of the products. You must add Molecules to Balance the atoms!!!

18 7 Steps to Balance 1. Check for Diatomic Molecules: (H 2, N 2, O 2, F 2, Cl2, Br2, & I2 1. Balance Metals 2. Balance Non-metals 3. Balance Oxygen 4. Balance Hydrogen 5. Recount All Atoms (Reduce if possible.)

19 Types of chemical reactions 0. Combustion Reaction - The reaction of a substance with oxygen, producing oxides and energy Fuel + oxygen  oxides + energy AB + oxygen  common oxides of A and B (ex AO, BO)

20 1. Synthesis Reaction -A chemical reaction in which two or more substances combine to form a more complex substance. A + B  AB Example: 2CO (g) + O 2(g) pt  2CO 2(g)

21 2. Decomposition reaction -A chemical reaction in which a compound is broken down into two or more simpler substances. AB  A + B Example: The decomposition of water. 2H 2 O (l) + electricity  2 H 2(g) + O 2(g)

22 3. Single Displacement reaction -A reaction of an element with a compound to produce a new element and a new compound. The reaction will only occur if the element is higher on the reactivity series than the metal in the compound. (Reactivity series on the next slide) A + BC  AC + B Example: Cu (s) + 2AgNO 3(aq)  2Ag (s) + Cu(NO 3 ) 2(aq)

23 4. Double displacement reaction - A reaction in which aqueous ionic compounds rearrange cations and anions, resulting in the formation of new compounds. AB + CD  AD + CB Example: Pb(NO 3 ) 2 (aq) + 2KI (aq)  PbI 2 (s) + 2KNO 3 (aq)

24 A reaction will only occur if the element is higher on the reactivity series than the metal in the compound. WHEN DOES A REACTION OCCUR?

25 Chemical reactions in solution A Solution is a homogenous mixture in which a pure substance, called the solute, is dissolved in another pure substance called the solvent. The solution is often an aqueous solution which is a solution where water is the solvent.

26 Review of Particle Theory 1. All Matter is made up of extremely tiny particles 2. Each Pure substance has its own kind of particles, different from the particles of other pure substances 3. Particles are always moving. Particles at a higher temperature are generally moving faster, on average than particles at a lower temperature. 4. Particles attract each other

27 Collision Model (theory) Atoms and molecules are constantly bumping into each other. If they are moving too slowly no reaction will occur. Molecules that are moving quickly enough may break bonds between atoms and the atoms may combine to form new molecules (new products). The exact energy required for a particular old bond to be broken and a new one to be formed is called the 'Activation Energy.

28 Collision Model (theory) Two factors increase the rate of reaction 1) Number of collisions 2) Number of effective/successful collisions

29 4 Factors that affect rates of reactions 1. Temperature When the reactants are heated, they bounce and contact more vigorously with other reactant molecules. This increases the number of successful collision and the rate of reaction. This is the most important factor.

30 4 Factors that affect rates of reactions 2. Concentration Concentration is defined as the number of molecules of reactants per unit volume. The more the concentration of reactant molecules, the higher the probability of collision due to their sheer number. Excess concentration may have no effect if one of the reactants is used up.

31 4 Factors that affect rates of reactions 3. Surface Area By increasing surface area, the number of molecules exposed for collisions is increased. This allows more collisions between molecules to occur and increases the rate of reaction.

32 4 Factors that affect rates of reactions 4. Catalyst Catalysts, are chemicals or substances that catalyze or promote a chemical reaction to occur and remaining unchanged in the end. They are like parts of an assembling mechanism that help making the final product but then detach themselves from it. They lower the activation energy.

33 Acids and Bases Acids are traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion [H + ] activity greater than in pure water, i.e. a pH less than 7.0.

34 When Acids are dissolved in water they release H +. Ex HCl (aq)  H + (aq) + Cl - (aq)

35 They also: Taste sour Are good conductors of electricity (they release H + ions when they are in water) React with compounds that contain carbonate Are generally quite reactive Inflict a sharp burning pain when handled Turn blue litmus red

36 Naming Acids There are two rules for naming acids when the chemical formula of an acid starts with H and has only one other non-metallic element StepExamples HCl (aq) HF (aq) 1.Start with the Prefix “hydro”hydroHydro 2.To the first part of the name of the non-metallic element, add the suffix “ic” and add the word “acid” Hydrochl oric acid Hydroflu oric acid

37 Naming Acids (with polyatomic ions) Some acids contain a polyatomic ion. When the polyatomic ion in an acid contains an oxygen atom (O) and its name ends in “ate”, the acid can be named by the steps shown below. StepExamples H 2 SO 4(aq) H 3 PO 4(aq) 1.Start with the name of the element in the polyatomic ion that is not oxygen sulphurphosphorus 2.Add the suffix “ic” and the word “acid”sulphuric acid phosphorusi c acid

38 Common acids Common nameFormulaSource or use Vinegar (acetic acid)HC 2 H 3 O 2 or HC 2 H 2 OOHSalad dressing Citric acidHC 6 H 7 O 7 Oranges, lemons Ascorbic acidHC 6 H 7 O 6 Vitamin C Lactic acidHC­ 3 H 5 O 3 Sour milk or tired muscles Sulfuric acidH 2 SO 4 Car batteries Table 1 Examples of common acids include

39 Acids are widely used in industry, they are used in many manufacturing processes including; fertilizers, explosives, refining oil, and electroplating materials. Acids that that react with metals and glass are described as being Corrosive. These acids can be dangerous to humans and the environment.

40 Base A base is most commonly thought of as an aqueous substance that can accept hydrogen ions. bases can commonly be thought of as any chemical compound that, when dissolved in water, gives a solution with a pH higher than 7.0.

41 When bases are released in water they release OH - ions Example NaOH (aq)­  Na + (aq) + OH - (aq)

42 They also: Taste bitter Are good conductors of electricity (They release OH - ions when dissolved in water) Break down proteins into smaller molecules May also be called alkaline Feel slippery when handled Turn Red litmus blue

43 Identifying and Naming Bases A base can also be identified from its name or its chemical formula. A substance is a base if its name begins with the name of a metallic ion and ends with the word “hydroxide.” A substance is also a base if: the chemical formula starts with a metallic ion or with the ammonium ion NH4 + AND the chemical formula ends with OH (called a hydroxyl group)

44 Naming Bases The name of a base can be determined from its chemical formula. Notice that all bases (in this class) are followed by the word “hydroxide.”

45 Naming Bases StepExamples KOH (aq) NH 4 OH (aq) 1.Write the name of the positively charged metallic ion that is at the beginning of the chemical formula. This step remains the same if the positively charged ion is a polyatomic ion. PotassiumAmmonium 1.Add the word “hydroxide”Potassium hydroxide Ammonium hydroxide

46 Table 2 Examples of some common bases Common NameFormulaSource or use Sodium hydroxideNaOHDrain cleaner Potassium hydroxideKOHSoap, cosmetics Aluminum hydroxideAl(OH)­ 3 Antacids Ammonium hydroxide NH­­ 4 OHWindow cleaner. Sodium bicarbonateNaHCO 3 Baking soda, used in baking Potassium sulphiteK 2 SO 3 Food preservative

47 Acid - Base Indicators: The most common indicator is found on "litmus" paper. It is red below pH 4.5 and blue above pH 8.2. Color Blue Litmus Red Litmus Acid turns red stays same Base stays sameturns blue

48 Acid - Base Indicators: Other commercial pH papers are able to give colors for every main pH unit. Universal Indicator, which is a solution of a mixture of indicators, is able to also provide a full range of colors for the pH scale.


50 The Strength of Acids and Bases The strength of acids and bases are not all equal. Some acids and bases are safe enough to eat while others can eat through clothing and metal.

51 The Strength of Acids and Bases Some acids and bases are classified as being strong while others are called weak. -Strong acids and bases are extremely reactive and corrosive. -Weak acids and bases are mostly unreactive and corrosive.

52 The pH Scale (power of Hydrogen) pH scale is used to represent how acidic or basic a solution is. The scale ranges from 0-14 with very acidic being 0, neutral being 7, and very basic being 14. Every point on the scale represents a 10 base exponent difference. Ex lemons (pH = 2.0) are 100 times more acidic than tomatoes (pH = 4.0) 7.0 is neutral (neither acidic nor basic (alkaline)). Acids range from 0-6.9 Bases range from 7.1 -14

53 The pH Scale (power of Hydrogen)

54 Neutralization Reactions What happens when an acid and a base are mixed? When an acid and a base are mixed they react to form products that have a pH of near or at 7, this is defined as a neutralization reaction. A Neutralization reaction always produces a salt and water.

55 Neutralization Reactions The products of a neutralization reaction of an acid and a base are salt and water. Acid + Base  Salt + water

56 Neutralization Reactions Example: Hydrochloric acid + sodium hydroxide  sodium chloride + water HCl (aq) + NaOH (aq)  NaCl + H 2 O

57 Applications: Antacids are examples of the use of a weak base to neutralize excess stomach acid. Antacids can be weak hydroxide bases such as magnesium hydroxide which reacts with excess stomach acid to form water and a salt. Antacids can also be bicarbonates such as sodium bicarbonate which reacts with the excess acid to form water, carbon dioxide and a salt

58 Chemistry Review Questions

59 Multiple Choice 1. In all chemical reactions the : a) mas of products is greater than the mass of the reactants b) mass of reactants is greater than the mass of the products c) mass of reactants always equal the mass of the products d) mass of products may be more or less than the mass of the reactants e) none of the above

60 Multiple Choice 2. A solution that tastes sour, turns litmus paper red and reacts with metals must be a(n): a) acidic solution b) basic solution c) neutral solution d) salt solution e) perfect solution

61 3. You are given a basic solution. Which of the following sets of properties will this solution have? a) taste bitter; feel slippery b) turn litmus paper blue; appear colourless in phenolphthalein c) conduct electricity; react with metal d) turn litmus paper pink/red; have no reaction with carbonates e) none of the above

62 Multiple Choice 4. If a substance is a strong base, its pH will be: a) between 1 and 3 b) between 4 and 6 c) 7 d) between 8 and 10 e) between 11 and 13

63 1. Balance the following skeleton (or formula) equations and identify the type of reaction. a) _2_ NaClO 3 → _2_ NaCl + _3_ O 2 Type of Reaction: Decomposition

64 1. Balance the following skeleton (or formula) equations and identify the type of reaction. b) _1_ H 2 SO 4 + _2_ NaOH  __1_ Na 2 SO 4 + __2_ HOH Type of Reaction: Double Displacement (not a neutralization reaction unless in aqueous solution).

65 Balance the following skeleton (or formula) equations and identify the type of reaction. C) _2__ Fe + _3__ Cl 2 → __2_ FeCl 3 Type of Reaction: Synthesis

66 Balance the following skeleton (or formula) equations and identify the type of reaction. D) _1__ Zn + __1_ FeCl 2 → _1___ ZnCl 2 + 1__ Fe Type of Reaction: Single Displacement

67 2. Complete the word equation and write the balanced chemical equation for the following neutralization reaction. Word Equation: Sulphric Acid Calcium Hydroxide Balanced Chemical Equation: Calcium Sulphate Water H 2 SO 4 + Ca(OH) 2  CaSO 4 + 2 HOH ++

68 3. Sodium reacts with hydrogen hydroxide to produce a new compound and a new element. a) Write a word equation for this reaction. Sodium + water  sodium hydroxide + hydrogen gas a) Write a balanced formula equation for this reaction. 2Na + 2HOH  2NaOH + H 2 (hydrogen is diatomic)

69 Part 3: Application 1. Acid rain is a major environmental problem in the world today. As acid rain falls into lakes, it can change the pH of those lakes, which in turn affects how well organisms can live in those lakes. Based on what you have learned about chemical reactions, suggest a procedure for reducing the impact acid rain makes on a lake. Answer will vary; ideas about chemical reactions, life needs a slightly acidic environment, neutralization reactions, other effects including hydrological cycle may also be mentioned in your response. The effects of adding basic compounds to lakes (good or bad).

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