General Chemistry Principles and Modern Applications Petrucci • Harwood • Herring 8th Edition Chapter 3: Chemical Compounds Dr. Burak Esat Fatih University Chem 107Fall 2013 1 Compound: A combination of two or more different elements. A substance composed of two or more elements chemically combined in fixed ratios by mass. Compounds are represented by chemical formulas indicating the fixed ratios of each elements chemically combined Water - H2O Carbon dioxide - CO2 Sodium Chloride - NaCl Iron(II) sulfide - FeS •Molecule Molecule: The smallest entity having the same elemental combination as •the compound. •Compounds are made of individual molecules 2 1 Chemical Formulas Empirical Formula - Shows the relative number of atoms of each element in the compound. It is the simplest formula, and is derived from masses of the elements. Molecular Formula - Shows the actual number of atoms of each element in the molecule of the compound. Structural Formula - Shows the actual number of atoms, and the bonds between them ; that is, the arrangement of atoms in the molecule. 3 Molecular compounds Structural Formula shows the order in which atoms are bonded together 4 2 Standard color scheme 5 Some molecules H2O2 CH3CH(OH)CH3 CH3CH2Cl P4O10 HCO2H 6 3 Chemical Formulas Empirical Formula - Shows the relative number of atoms of each element in the compound. It is the simplest formula, and is derived from masses of the elements. Molecular Formula - Shows the actual number of atoms of each element in the molecule of the compound. Structural Formula - Shows the actual number of atoms, and the bonds between them ; that is, the arrangement of atoms in the molecule. 7 Some Examples of Compounds with the Same Elemental Ratio’s Empirical Formula Molecular Formula CH2(unsaturated Hydrocarbons) C2H4 , C3H6 , C4H8 OH or HO H2 O2 S S8 P P4 Cl Cl2 CH2O (carbohydrates) C6H12O6 8 4 Some Compounds with Empirical Formula CH2O (Composition by Mass 40.0% C, 6.71% H, 53.3%O) Molecular Formula M (g/mol) Name CH2O 30.03 Formaldehyde C2H4O2 60.05 Acetic acid C3H6O3 90.08 Lactic acid C4H8O4 120.10 Erythrose C5H10O5 150.13 Ribose C6H12O6 180.16 Glucose Use or Function Disinfectant; Biological preservative Acetate polymers; vinegar ( 5% solution) Causes milk to sour; forms in muscle during exercise Forms during sugar metabolism Component of many nucleic acids and vitamin B2 Major nutrient for energy 9 in cells Mole • The Mole is based upon the definition: • The amount of substance that contains as many elementary parts (atoms, molecules, or other) as there are atoms in exactly 12 grams of carbon 12. • 1 Mole = 6.022045 x 1023 particles 10 5 One Mole of Common Substances CaCO3 100.09 g Oxygen Gas (O2) 32.00 g Copper (Cu) 63.55 g Water (H2O) 18.02 g 11 Mole - Mass Relationships of Elements Element Atom/Molecule Mass 1 atom of H = 1.008 amu Mole Mass Number of Atoms 1 mole of H = 1.008 g = 6.022 x 1023 atoms 1 atom of Fe = 55.85 amu 1 mole of Fe = 55.85 g = 6.022 x 1023 atoms 1 atom of S = 32.07 amu 1 mole of S = 32.07 g = 6.022 x 1023 atoms 1 atom of O = 16.00 amu 1 mole of O = 16.00 g = 6.022 x 1023 atoms 1 molecule of O2 = 32.00 amu 1 mole of O2 = 32.00 g = 6.022 x 1023 molecule 1 molecule of S8 = 205.952 amu 12 1 mole of S8 = 205.952 g = 6.022 x 1023 molecules 6 Information Contained in the Chemical Formula of Glucose C6H12O6 Carbon (C) Hydrogen (H) Oxygen (O) Atoms/molecule of compound 6 atoms 12 atoms 6 atoms Moles of atoms/ mole of compound 6 moles of atoms 12 moles of atoms 6 moles of atoms Atoms/mole of compound 6(6.022 x 1023) 12(6.022 x 1023) 6(6.022 x 1023) atoms atoms atoms Mass/molecule of compound 6(12.01 amu) =72.06 amu Mass/mole of compound 72.06 g 12(1.008 amu) =12.10 amu 12.10 g 6(16.00 amu) =96.00 amu 96.00 g 13 Calculate the Molecular Mass of Glucose: C6H12O6 • Carbon 6 x 12.011 g/mol = 72.066 g • Hydrogen 12 x 1.008 g/mol = 12.096 g • Oxygen 6 x 15.999 g/mol = 95.994 g 180.156 g 14 7 % Composition H OH Glucose H O HO HO H H H OH OH Molecular formula C6H12O6 Empirical formula CH2O Molecular Mass: Use the naturally occurring mixture of isotopes, 6 x 12.01 + 12 x 1.01 + 6 x 16.00 = 180.18 Exact Mass: Use the most abundant isotopes, 6 x 12.000000 + 12 x 1.007825 + 6 x 15.994915 = 180.06339 15 Chemical Composition Halothane C2HBrClF3 Mole ratio nC/nhalothane Mass ratio mC/mhalothane M(C2HBrClF3) = 2MC + MH + MBr + MCl + 3MF = (2 x 12.01) + 1.01 + 79.90 + 35.45 + (3 x 19.00) = 197.38 g/mol 16 8 Example 3.4 Calculating the Mass Percent Composition of a Compound Calculate the molecular mass M(C2HBrClF3) = 197.38 g/mol For one mole of compound, formulate the mass ratio and convert to percent: %C = (2 ×12.01) g ×100% = 12.17% 197.38 g 17 Example 3-4 (2 ×12.01) g ×100% = 12.17% 197.38 g 1.01g ×100% = 0.51% %H = 197.38 g 79.90 g % Br = ×100% = 40.48% 197.38 g 35.45 g %Cl = ×100% = 17.96% 197.38 g (3 ×19.00) g %F = ×100% = 28.88% 197.38 g %C = 18 9 Mass Percent Composition of Na2SO4 Na2SO4 = 2 atoms of Sodium + 1 atom of Sulfur + 4 atoms of Oxygen Elemental masses Percent of each Element 2 x Na = 2 x 22.99 = 45.98 1 x S = 1 x 32.07 = 32.07 4 x O = 4 x 16.00 = 64.00 142.05 Atomic Masses from Periodic Table % Na = Mass Na / Total mass x 100% % Na = (45.98 / 142.05) x 100% =32.37% % S = Mass S / Total mass x 100% % S = (32.07 / 142.05) x 100% = 22.58% % O = Mass O / Total mass x 100% % O = (64.00 / 142.05) x 100% = 45.05% Check % Na + % S + % O = 100% 32.37% + 22.58% + 45.05% = 100.00% Steps to Determine Empirical Formulas Masses (g) of Individual Elements xA+yB AxBy Molar Mass (g/mol ) Moles of Each Element use no. of moles as subscripts Preliminary Formula change to integer subscripts Empirical Formula 20 10 Determining Empirical Formulas from Masses of Elements - I Problem: The elemental analysis of a sample compound gave the following results: 5.677g Na, 6.420 g Cr, and 7.902 g O. What is the empirical formula and name of the compound? Plan: First we have to convert mass of the elements to moles of the elements using the molar masses. Then we construct a preliminary formula and name of the compound. Solution: Finding the moles of the elements: 1 mol Na Moles of Na = 5.678 g Na x 22.99 g Na = 0.2469 mol Na 1 mol Cr Moles of Cr = 6.420 g Cr x 52.00 g Cr = 0.12347 mol Cr Moles of O = 7.902 g O x 1 mol O = 0.4939 mol O 16.00 g O 21 Determining Empirical Formulas from Masses of Elements - II Constructing the preliminary formula: Na0.2469 Cr0.1235 O0.4939 Converting to integer subscripts (dividing all by smallest subscript): Na1.99 Cr1.00 O4.02 Rounding off to whole numbers: Na2CrO4 Sodium Chromate 22 11 Establishing Formulas from Experimentally Determined Percent Composition 5 Step approach: 1. 2. 3. 4. 5. Choose an arbitrary sample size (100g). Convert masses to amounts in moles. Write a formula. Convert formula to small whole numbers. Multiply all subscripts by a small whole number to make the subscripts integral. 23 Determining the Molecular Formula from Elemental Composition and Molar Mass - I Problem: The sugar burned for energy in cells of the body is Glucose (M = 180.16 g/mol), elemental analysis shows that it contains 40.00 mass % C, 6.719 mass % H, and 53.27 mass % O. (a) Determine the empirical formula of glucose. (b) Determine the molecular formula. Plan: We are only given mass %, and no weight of the compound so we will assume 100g of the compound, and % becomes grams, and we can do as done previously with masses of the elements. Solution: Mass Carbon = 40.00% x 100g/100% = 40.00 g C Mass Hydrogen = 6.719% x 100g/100% = 6.719g H Mass Oxygen = 53.27% x 100g/100% = 53.27 g O 99.989 g Cmpd 24 12 Determining the Molecular Formula from Elemental Composition and Molar Mass - II Converting from Grams of Elements to moles: Moles of C = Mass of C x 1 mole C = 3.3306 moles C 12.01 g C 1 mol H Moles of H = Mass of H x = 6.6657 moles H 1.008 g H Moles of O = Mass of O x 1 mol O = 3.3294 moles O 16.00 g O Constructing the preliminary formula C 3.33 H 6.67 O 3.33 Converting to integer subscripts, divide all subscripts by the smallest: C 3.33/3.33 H 6.667 / 3.33 O3.33 / 3.33 = CH2O 25 Determining the Molecular Formula from Elemental Composition and Molar Mass - III (b) Determining the Molecular Formula: The formula weight of the empirical formula is: 1 x C + 2 x H + 1 x O = 1 x 12.01 + 2 x 1.008 + 1 x 16.00 = 30.03 Whole-number multiple = = M of Glucose empirical formula mass = 180.16 = 6.00 = 6 30.03 Therefore the Molecular Formula is: C1x6H2x6O1x6 = C6H12O6 26 13 Adrenaline Is a Very Important Compound in the Body - I • Analysis gives : • C = 56.8 % • H = 6.50 % • O = 28.4 % • N = 8.28 % • Calculate the Empirical Formula 27 Adrenaline - II • • • • • • • • • • Assume 100g! C = 56.8 g C/(12.01 g C/ mol C) = 4.73 mol C H = 6.50 g H/( 1.008 g H / mol H) = 6.45 mol H O = 28.4 g O/(16.00 g O/ mol O) = 1.78 mol O N = 8.28 g N/(14.01 g N/ mol N) = 0.591 mol N Divide by 0.591 = C = 8.00 mol C = 8.0 mol C or H = 10.9 mol H = 11.0 mol H O = 3.01 mol O = 3.0 mol O C8H11O3N N = 1.00 mol N = 1.0 mol N 28 14 Combustion Train for the Determination of the Chemical Composition of Organic Compounds. CnHm + (n+ m ) O2 = n CO2(g) +m H2O(g) 2 2 29 Fig. 3.4 Combustion Analysis 30 15 Ascorbic Acid ( Vitamin C ) - I Contains C , H , and O • Upon combustion in excess oxygen, a 6.49 mg sample yielded 9.74 mg CO2 and 2.64 mg H2O • Calculate it’s Empirical formula! • C: 9.74 x10-3g CO2 x(12.01 g C/44.01 g CO2) = 2.65 x 10-3 g C • H: 2.64 x10-3g H2O x (2.016 g H2/18.02 gH2O) = 2.92 x 10-4 g H • Mass Oxygen = 6.49 mg - 2.65 mg - 0.30 mg = 3.54 mg O 31 Vitamin C Combustion - II • C = 2.65 x 10-3 g C / ( 12.01 g C / mol C ) = = 2.21 x 10-4 mol C • H = 0.295 x 10-3 g H / ( 1.008 g H / mol H ) = = 2.92 x 10-4 mol H • O = 3.54 x 10-3 g O / ( 16.00 g O / mol O ) = = 2.21 x 10-4 mol O • Divide each by 2.21 x 10-4 • C = 1.00 • H = 1.32 • O = 1.00 Multiply each by 3 C3H4O3 = 3.00 = 3.0 = 3.96 = 4.0 = 3.00 = 3.0 32 16 Determining a Chemical Formula from Combustion Analysis - I Problem: Erythrose (M = 120 g/mol) is an important chemical compound as a starting material in chemical synthesis, and contains Carbon Hydrogen, and Oxygen. Combustion analysis of a 700.0 mg sample yielded 1.027 g CO2 and 0.4194 g H2O. Plan: 1) We find the masses of Hydrogen and Carbon using the mass fractions of H in H2O, and C in CO2. 2) The mass of Carbon and Hydrogen are subtracted from the sample mass to get the mass of Oxygen. 3) We then calculate moles, and 4) Construct the empirical formula, and 5) From the given molar mass we can calculate the molecular33 formula. Determining a Chemical Formula from Combustion Analysis - II Calculating the mass fractions of the elements: Mass fraction of C in CO2 = mol C x M of C = mass of 1 mol CO2 = 1 mol C x 12.01 g C/ 1 mol C = 44.01 g CO2 0.2729 g C / 1 g CO2 mol H x M of H = mass of 1 mol H2O 2 mol H x 1.008 g H / 1 mol H = = 0.1119 g H / 1 g H2O 18.02 g H2O Mass fraction of H in H2O = Calculating masses of C and H Mass of Element = mass of compound x mass fraction of element 34 17 Determining a Chemical Formula from Combustion Analysis - III 0.2729 g C = 0.2803 g C 1 g CO2 0.1119 g H Mass (g) of H = 0.4194 g H2O x = 0.04693 g H 1 g H2O Mass (g) of C = 1.027 g CO2 x Calculating the mass of O: Mass (g) of O = Sample mass -( mass of C + mass of H ) = 0.700 g - 0.2803 g C - 0.04693 g H = 0.37277 g O Calculating moles of each element: C = 0.2803 g C / 12.01 g C/ mol C = 0.02334 mol C H = 0.04693 g H / 1.008 g H / mol H = 0.04656 mol H O = 0.37277 g O / 16.00 g O / mol O = 0.02330 mol O C0.02334H0.04656O0.02330 = CH2O formula weight = 30 g / formula 120 g /mol / 30 g / formula = 4 formula units / cpd = C4H8O4 35 Oxidation States Metals tend to lose electrons. Non-metals tend to gain electrons. Na -> Na+ + e- Cl + e- -> Cl- Reducing agents Oxidizing agents We use the Oxidation State to keep track of the number of electrons that have been gained or lost by an element. 36 18 Ionic Bonding - An ionic bond is a chemical bond that results from an electrostatic attraction among oppositely charged ions in a compound. They form when electrons are transferred from one atom to another to form ions. Mono-atomic ions form binary ionic compounds Na [Ne] 3s1 Na [Ne]+ Na+ Cl [Ne] 3s2 3p5 + + Cl [Ar]- Cl- “Cations” - Metal atoms lose electrons to form “ + ” ions. 37 “Anions” - Nonmetal atoms gain electrons to form “ - ” ions. Fig. 2.18 38 19 Rules for Oxidation States 1. The oxidation state (OS) of an individual atom in a free element is 0. 2. The total of the OS in all atoms in: i. Neutral species is 0. ii. Ionic species is equal to the charge on the ion. 3. In their compounds, the alkali metals and the alkaline earths have OS of +1 and +2 respectively. 4. In compounds the OS of fluorine is always –1 39 Rules for Oxidation States 5. In compounds, the OS of hydrogen is usually +1 6. In compounds, the OS of oxygen is usually –2. 7. In binary (two-element) compounds with metals: i. Halogens have OS of –1, ii. Group 16 have OS of –2 and iii. Group 15 have OS of –3. 40 20 Example 3-7 Assigning Oxidation States. What is the oxidation state of the underlined element in each of the following? a) P4; b) Al2O3; c) MnO4-; d) NaH a) P4 is an element. P OS = 0 b) Al2O3: O is –2. O3 is –6. Since (+6)/2=(+3), Al OS = +3. c) MnO4-: net OS = -1, O4 is –8. Mn OS = +7. d) NaH: net OS = 0, rule 3 beats rule 5, Na OS = +1 and H OS = -1. 41 Fig. 2.23 42 21 Fig. 2.20 43 Predicting the Ion an Element Will Form in Chemical Reactions Problem: What mono-atomic ions will each of the elements form? (a) Barium(z=56) (b) Sulfur(z=16) (c) Titanium(z =22) (d) Fluorine(z=9) Plan: We use the “z” value to find the element in the periodic table and the nearest noble gas. Elements that lie after a noble gas will loose electrons, and those before a noble gas will gain electrons. Solution: (a) Ba+2, Barium is an alkaline earth element, Group 2A, and is expected to loose two electrons to attain the same number of electrons as the noble gas Xenon! (b) S -2, Sulfur is in the Oxygen family, Group 6A, and is expected to gain two electrons to attain the same number of electrons as the noble gas Argon! (c) Ti+4, Titanium is in Group 4B, and is expected to loose 4 electrons to attain the same number of electrons as the noble gas Argon! (d) F -, Fluorine is in a halogen, Group 7A, and is expected to gain one electron, to attain the same number of electrons as the noble gas Neon! 44 22 3-5 Naming Compounds: Organic and Inorganic Compounds Trivial names are used for common compounds. A systematic method of naming compounds is known as a system of nomenclature. Organic compounds Inorganic compounds Lead (IV) oxide Lead (II) oxide 45 3-6 Names and Formulas of Inorganic Compounds Binary Compounds of Metals and Nonmetals 46 23 Table 2.3 (p. 67) Common Mono-atomic Ions Cations Charge Formula 1+ 2+ 3+ H+ Li+ Na+ K+ Cs+ Ag+ Mg2+ Ca2+ Sr2+ Ba2+ Zn2+ Cd2+ Al3+ Name hydrogen lithium sodium potassium cesium silver magnesium calcium strontium barium zinc cadmium aluminum Anions Charge Formula HFCl Br I- 1- Name hydride fluoride chloride bromide iodide 2- O2S2 - oxide sulfide 3- N 3- nitride 47 Listed by charge; those in boldface are most common Give the Name and Chemical Formulas of the Compounds Formed from the Following Pairs of Elements a) Sodium and Oxygen Na2O Sodium Oxide b) Zinc and Chlorine ZnCl2 Zinc Chloride c) Calcium and Fluorine CaF2 Calcium Fluoride d) Strontium and Nitrogen Sr3N2 Strontium Nitride e) Hydrogen and Iodine HI Hydrogen Iodide f) Scandium and Sulfur Sc2S3 Scandium Sulfide 48 24 Some Metals That Form More than One Oxidation State Element Chromium Cobalt Copper Iron Lead Manganese Mercury Tin Ion Formula Cr+2 Cr+3 Co+2 Co+3 Cu+1 Cu+2 Fe+2 Fe+3 Pb+2 Pb+4 Mn+2 Mn+3 Hg2+2 Hg+2 Sn+2 Sn+4 Table 2.4 (p. 69) Systematic Name Chromium (II) Chromium (III) Cobalt (II) Cobalt (III) Copper (I) Copper (II) Iron (II) Iron (III) Lead (II) Lead (IV) Manganese (II) Manganese (III) Mercury (I) Mercury (II) Tin (II) Tin (IV) Common Name Chromous Chromic Cuprous Cupric Ferrous Ferric Mercurous Mercuric Stannous Stannic 49 Determining Names and Formulas of Ionic Compounds of Elements That Form More than One Ion Give the systematic names for the formulas or the formulas for the names of the following compounds. a) Iron III Sulfide - Fe is +3, and S is -2 therefore the compound is: Fe2S3 -1 b) CoF2 - the anion is Fluoride (F ) and there are two F -1, the cation is Cobalt and it must be Co+2 therefore the compound is: Cobalt (II) Fluoride c) Stannic Oxide - Stannic is the common name for Tin (IV), Sn+4, the Oxide ion is O-2, therefore the formula of the compound is: SnO2 d) NiCl3 - The anion is chloride (Cl-1), there are three anions, so the Nickel cation is Ni+3, therefore the name of the compound is: 50 Nickel (III) Chloride 25 51 Rules for Families of Oxoanions Families with Two Oxoanions The ion with more O atoms takes the nonmetal root and the suffix “-ate”. The ion with fewer O atoms takes the nonmetal root and the suffix “-ite”. Families with Four Oxoanions (usually a Halogen) The ion with most O atoms has the prefix “per-”, the nonmetal root and the suffix “-ate”. The ion with one less O atom has just the suffix “-ate”. The ion with two less O atoms has the just the suffix “-ite”. The ion with three less O atoms has the prefix “hypo-” and52the suffix “-ite”. 26 Examples of Names and Formulas of Oxoanions and Their Compounds - I • • • • • • • • • • • • KNO2 Potassium Nitrite BaSO3 Barium Sulfite Mg(NO3)2 Magnesium Nitrate Na2SO4 Sodium Sulfate LiClO4 Lithium Perchlorate Ca(BrO)2 Calcium Hypobromite NaClO3 Sodium Chlorate Al(IO2)3 Aluminum Iodite RbClO2 Rubidium Chlorite KBrO3 Potassium Bromate CsClO Cesium Hypochlorite LiIO4 Lithium Periodate 53 Examples of Names and Formulas of Oxoanions and Their Compounds - II • • • • • • • • • • • • Calcium Nitrate Ca(NO3)2 Ammonium Sulfite (NH4)2SO3 Strontium Sulfate SrSO4 Lithium Nitrite LiNO2 Potassium Hypochlorite KClO Lithium Perbromate LiBrO4 Rubidium Chlorate RbClO3 Calcium Iodite Ca(IO2)2 Ammonium Chlorite NH4ClO2 Boron Bromate B(BrO3)3 Sodium Perchlorate NaClO4 Magnesium Hypoiodite Mg(IO)2 54 27 55 Naming Oxoanions - Examples per hypo Root Suffixes “ ” ate “ ” ate “ ” ite “ ” ite Chlorine Bromine perchlorate perbromate [ ClO4-] [ BrO4-] No. of O atoms Prefixes Iodine periodate [ IO4-] chlorate [ ClO3-] bromate [BrO3-] iodate [ IO3-] chlorite [ ClO2-] bromite [ BrO2-] iodite [ IO2-] hypochlorite hypobromite hypoiodite [ ClO -] [ BrO -] [ IO -] 56 28 Naming Acids 1) Binary acids solutions form when certain gaseous compounds dissolve in water. For example, when gaseous hydrogen chloride (HCl) dissolves in water, it forms a solution called hydrochloric acid. Prefix hydro- + anion nonmetal root + suffix -ic + the word acid hydrochloric acid 2) Oxoacid names are similar to those of the oxoanions, except for two suffix changes: Anion “-ate” suffix becomes an “-ic” suffix in the acid. Anion “-ite” suffix becomes an “-ous” suffix in the acid. The oxoanion prefixes “hypo-” and “per-” are retained. Thus, BrO4is perbromate, and HBrO4 is perbromic acid; IO2- is iodite, and HIO2 is iodous acid. 57 Binary Acids Acids produce H+ when dissolved in water. They are compounds that ionize in water. Emphasize the fact that a molecule is an acid by altering the name. HCl hydrogen chloride hydrochloric acid HF hydrogen fluoride hydrofluoric acid 58 29 Determining Names and Formulas of Anions and Acids Problem: Name the following anions and give the names and formulas of the acid solutions derived from them: a) I b) BrOc) SO3-2 d) NO3e) CN Solution: a) The anion is Iodide; and the acid is Hydroiodic acid, HI b) The anion is hypobromite; and the acid is hypobromous acid, HBrO c) The anion is Sulfite; and the acid is Sulfurous acid, H2SO3 d) The anion is Nitrate; and the acid is Nitric acid, HNO3 e) The anion is Cyanide; and the acid is Hydrocyanic acid, HCN 59 Some Compounds of Greater Complexity • Effect of Moisture – Blue anhydrous • CoCl2 – Pink hexahydrate • CoCl2• 6 H2O 6 mol H2O × %H2O = 18.02 g H2O 1 mol H2O 237.9 g CoCl2• 6 H2O × 100% = 45.45% H2O 60 30 Hydrates Compounds Containing Water Molecules MgSO4 7H2O Magnesium Sulfate heptahydrate CaSO4 2H2O Calcium Sulfate dihydrate Ba(OH)2 Barium Hydroxide octahydrate 8H2O CuSO4 5H2O Copper II Sulfate pentahydrate Na2CO3 10H2O Sodium Carbonate decahydrate 61 Determining Names and Formulas of Ionic Compounds Containing Polyatomic Ions a) BaCl2 5 H2O Ba+2 is the cation Barium, Cl- is the Chloride anion. There are five water molecules therefore the name is: Barium Chloride Pentahydrate b) Magnesium Perchlorate Magnesium is the Mg+2 cation, and perchlorate is the ClO4- anion, therefore we need two perchlorate anions for each Mg cation therefore the formula is: Mg( ClO4)2 c) (NH4)2SO3 NH4+ is the ammonium ion, and SO3-2 is the sulfite anion, therefore the name is: Ammonium Sulfite d) Calcium Nitrate Calcium is the Ca+2 cation, and nitrate is the NO3- anion, therefore the formula is: 62 Ca(NO3)2 31 Binary Compounds of Two Non-Metals Molecular compounds usually write the positive OS element first. HCl hydrogen chloride Some pairs form more than one compound mono 1 penta 5 di 2 hexa 6 tri 3 hepta 7 tetra 4 octa 8 63 Names and Formulas of Binary Molecular (Covalent) Compounds 1) The element with the lower group number in the periodic table is the first word in the name; the element with the higher group number is the second word. (Important exception: When the compound contains oxygen and a halogen, the halogen is named first.) 2) If both elements are in the same group, the one with the higher period number is named first. 3) The second element is named with its root and the suffix “-ide.” 4) Covalent compounds have Greek numerical prefixes to indicate the number of atoms of each element in the compound. The first word has a prefix only when more than one atom of the element 64 is present; the second word always has a numerical prefix. 32 65 66 33 67 68 34 Naming Alkanes Alkanes are hydrocarbons that are called “saturated” hydrocarbons, they contain only single bonds, no multiple bonds ! Alkanes have the general formula --- C n H 2n+2 Each carbon atom has four bonds to others atoms ! The names for alkanes all end in -ane Alkanes are found in three distinct groups: a) Straight chain hydrocarbons b) Branched chain hydrocarbons c) Cyclic hydrocarbons 69 70 35 Structural Isomers Isomers have the same molecular formula but have different arrangements of atoms in space. Are the following pairs isomers? (c) H 71 The First 10 Straight-Chain Alkanes Name Formula Structural Formulas Methane Ethane CH4 C2H6 Propane Butane C3H8 C4H10 CH3-CH2-CH3 Pentane Hexane C5H12 C6H14 CH3-(CH2)3-CH3 Heptane Octane C7H16 C8H18 Nonane Decane C9H20 C10H22 H H C H H H H H C C H H H CH3-(CH2)2-CH3 CH3-(CH2)4-CH3 CH3-(CH2)5-CH3 CH3-(CH2)6-CH3 CH3-(CH2)7-CH3 Table 2.7 CH3-(CH2)8-CH72 3 36 Functional Groups – Alcohols 73 Functional Groups – Carboxylic Acid 74 37 Two Compounds with Molecular Formula C2H6O Property Ethanol Dimethyl Ether M (g/mol) 46.07 Color Colorless Melting point - 117oC Boiling point 78.5oC Density (at 20oC) 0.789 g/mL Use Intoxicant in H H alcoholic beverages H C C H H O H H 46.07 Colorless - 138.5oC - 25oC 0.00195 g/mL In refrigeration H H C O C H 75 Table 3.4 H H 76 38 77 78 39