Chemical, Structural Formula, and Models Compe.ppt
- 1. Compounds & Molecules Compounds & Molecules NaCl, salt NaCl, salt Buckyball, C Buckyball, C60 60 Ethanol, C Ethanol, C2 2H H6 6O O Molecule: The smallest identifiable unit that retains the physical and chemical properties of the pure substances.
- 2. Compounds & Molecules Compounds & Molecules • COMPOUND COMPOUND is a combination of 2 or is a combination of 2 or more elements in definite ratios by mass. more elements in definite ratios by mass. • The character of each element is lost when The character of each element is lost when forming a compound (e.g., think of NaCl). forming a compound (e.g., think of NaCl). • MOLECULES MOLECULES are the smallest units of a are the smallest units of a compound that retains the characteristics of compound that retains the characteristics of the compound. the compound.
- 3. MOLECULAR FORMULAS MOLECULAR FORMULAS • Formula for glycine is Formula for glycine is C C2 2H H5 5NO NO2 2 (description of the composition) (description of the composition) • In one molecule there are In one molecule there are – 2 C atoms 2 C atoms – 5 H atoms 5 H atoms – 1 N atom 1 N atom – 2 O atoms 2 O atoms
- 4. CONDENSED FORMULAS CONDENSED FORMULAS • Formula for glycine is Formula for glycine is NH NH2 2CH CH2 2CO CO2 2H H (composition and functional groups) (composition and functional groups) • In one molecule there are In one molecule there are – 1 NH 1 NH2 2 (amine group) (amine group) – 1 CH 1 CH2 2 group group – 1 CO 1 CO2 2H group H group
- 5. STRUCTURAL FORMULAS STRUCTURAL FORMULAS • Show how the atoms are attached within a Show how the atoms are attached within a molecule molecule • The lines between atoms represent chemical The lines between atoms represent chemical bonds that hold the atoms together. bonds that hold the atoms together.
- 6. WRITING FORMULAS WRITING FORMULAS • Can also write glycine as the condensed formula condensed formula H2NCH2COOH showing functional groups (atom ordering and connectivity) • or in the form of a structural structural formula formula showing how atoms are attached to each other (bond orders) C H H C H H O O H N
- 7. MOLECULAR MODELING MOLECULAR MODELING C H H C H H O O H N Ball & stick Ball & stick Space-filling Space-filling Drawing of glycine Drawing of glycine An even higher level of structural detail
- 8. Resources for Resources for Molecular Modeling Molecular Modeling • Modeling software Modeling software –CAChe CAChe ( (General Chemistry Interactive General Chemistry Interactive CD-ROM) CD-ROM) –Rasmol Rasmol –Molden Molden –Gaussview Gaussview –Maestro Maestro
- 9. MOLECULAR WEIGHT MOLECULAR WEIGHT AND MOLAR MASS AND MOLAR MASS Molecular weight Molecular weight = sum of the = sum of the atomic weights of all atoms in the atomic weights of all atoms in the molecule. molecule. Molar mass Molar mass = molecular weight in = molecular weight in grams per mol. grams per mol.
- 10. What is the molar What is the molar mass of ethanol, mass of ethanol, C C2 2H H6 6O? O? 1 mol contains 1 mol contains 2 moles of C (12.01 g C/1 mol) = 24.02 g C 2 moles of C (12.01 g C/1 mol) = 24.02 g C 6 moles of H (1.01 g H/1 mol) = 6.06 g H 6 moles of H (1.01 g H/1 mol) = 6.06 g H 1 mol of O (16.00 g O/1 mol) = 16.00 g O 1 mol of O (16.00 g O/1 mol) = 16.00 g O TOTAL = TOTAL = molar mass = 46.08 g/mol molar mass = 46.08 g/mol
- 11. • Formula = • Molar mass = Tylenol Tylenol C C8 8H H9 9NO NO2 2 151.2 g/mol 151.2 g/mol
- 13. How many How many moles moles of alcohol (C of alcohol (C2 2H H6 6O) O) are there in a “standard” can of beer are there in a “standard” can of beer if there are 21.3 g of C if there are 21.3 g of C2 2H H6 6O? O? (a) Molar mass of C2H6O = 46.08 g/mol (b) Calc. moles of alcohol 21.3 g • 1 mol 46.08 g = 0.462 mol
- 14. How many How many molecules molecules of alcohol are of alcohol are there in a “standard” can of beer if there in a “standard” can of beer if there are 21.3 g of C there are 21.3 g of C2 2H H6 6O? O? = 2.78 x 1023 molecules We know there are 0.462 mol of C2H6O. 0.462 mol • 6.022 x 1023 molecules 1 mol
- 15. How many How many atoms of C atoms of C are there in are there in a “standard” can of beer if there are a “standard” can of beer if there are 21.3 g of C 21.3 g of C2 2H H6 6O? O? = 5.57 x 1023 C atoms There are 2.78 x 1023 molecules. Each molecule contains 2 C atoms. Therefore, the number of C atoms is 2.78 x 1023 molecules • 2 C atoms 1 molecule
- 16. Molecular & Ionic Compounds Molecular & Ionic Compounds Heme Heme NaCl NaCl Molecular compounds consist of discrete molecules Molecular compounds consist of discrete molecules Ionic compounds consist of discrete ions Ionic compounds consist of discrete ions
- 17. IONS AND IONIC COMPOUNDS IONS AND IONIC COMPOUNDS • IONS IONS are atoms or groups of atoms with a positive are atoms or groups of atoms with a positive or negative charge. or negative charge. • Taking away Taking away an electron from an atom gives a an electron from an atom gives a CATION CATION with a with a positive charge positive charge • Adding Adding an electron to an atom gives an an electron to an atom gives an ANION ANION with a with a negative charge negative charge. .
- 18. Forming Cations & Anions Forming Cations & Anions A A CATION CATION forms forms when an when an atom atom loses loses one or one or more electrons. more electrons. An An ANION ANION forms forms when an when an atom atom gains gains one or one or more electrons more electrons Mg --> Mg2+ + 2 e- F + e- --> F- oxidation reduction
- 20. PREDICTING ION CHARGES PREDICTING ION CHARGES In general In general • metals metals (Mg) (Mg) lose electrons lose electrons ---> ---> cations cations • nonmetals nonmetals (F) (F) gain electrons gain electrons ---> ---> anions anions
- 21. Charges on Common Ions Charges on Common Ions +3 -4 -1 -2 -3 +1 +2 By losing or gaining e-, atom has same number of By losing or gaining e-, atom has same number of electrons as electrons as nearest Group 8A atom nearest Group 8A atom. . Cation charge=group # Cation charge=group # Anion charge=group #-8 Anion charge=group #-8
- 22. Predicting Charges on Monatomic Ions Predicting Charges on Monatomic Ions
- 23. METALS METALS M ---> n e- + M M ---> n e- + Mn+ n+ where n = periodic group where n = periodic group Na Na+ + sodium ion sodium ion Mg Mg2+ 2+ magnesium ion magnesium ion Al Al3+ 3+ aluminum ion aluminum ion Transition metals --> M Transition metals --> M2+ 2+ or M or M3+ 3+ are common are common Fe Fe2+ 2+ iron(II) ion iron(II) ion Fe Fe3+ 3+ iron(III) ion iron(III) ion
- 24. NONMETALS NONMETALS NONMETAL + n e- ------> X NONMETAL + n e- ------> Xn- n- where n = 8 - Group no. where n = 8 - Group no. C C4- 4- ,carbide ,carbide N N3- 3- , nitride , nitride O O2- 2- , oxide , oxide S S2- 2- , sulfide , sulfide F F- - , fluoride , fluoride Cl Cl- - , chloride , chloride Group 7A Group 6A Group 4A Group 5A Br Br- - , bromide , bromide I I- - , iodide , iodide
- 25. Ion Formation Ion Formation Reaction of aluminum and bromine
- 26. POLYATOMIC IONS POLYATOMIC IONS CD Screen 3.6 CD Screen 3.6 Groups of atoms with a charge. Groups of atoms with a charge. MEMORIZE MEMORIZE the names and formulas of common the names and formulas of common polyatomic ions listed in Table 3.1, page 107 (next slide) polyatomic ions listed in Table 3.1, page 107 (next slide)
- 28. Polyatomic Ions Polyatomic Ions NH NH4 4 + + ammonium ion ammonium ion One of the few common One of the few common polyatomic cations polyatomic cations
- 29. Polyatomic Ions Polyatomic Ions (oxoanions) (oxoanions) HNO HNO3 3 nitric acid nitric acid NO NO3 3 - - nitrate ion nitrate ion Prefix per- and suffix –ate: largest # Prefix per- and suffix –ate: largest # Suffix -ate : greater # of oxygen atoms Suffix -ate : greater # of oxygen atoms Suffix -ite : smaller # of oxygen atoms Suffix -ite : smaller # of oxygen atoms Prefix hypo- and suffix –ite: smallest # Prefix hypo- and suffix –ite: smallest #
- 30. SO SO4 4 2- 2- sulfate ion sulfate ion SO SO3 3 2- 2- sulfite ion sulfite ion Polyatomic Ions Polyatomic Ions
- 31. NO NO3 3 - - nitrate ion nitrate ion NO NO2 2 - - nitrite ion nitrite ion Polyatomic Ions Polyatomic Ions
- 32. Polyatomic Ions Polyatomic Ions CO CO3 3 2- 2- carbonate ion carbonate ion HCO HCO3 3 - - bicarbonate ion bicarbonate ion hydrogen carbonate hydrogen carbonate
- 33. PO PO4 4 3- 3- phosphate ion phosphate ion CH CH3 3CO CO2 2 - - acetate ion acetate ion Polyatomic Ions Polyatomic Ions
- 34. CATION CATION + + ANION ANION ---> ---> COMPOUND COMPOUND A neutral compd. A neutral compd. requires requires equal number of + equal number of + and - charges. and - charges. COMPOUNDS COMPOUNDS FORMED FORMED FROM IONS FROM IONS Na Na+ + + Cl + Cl- - --> NaCl --> NaCl
- 35. IONIC COMPOUNDS IONIC COMPOUNDS NH4 + Cl- ammonium chlor ammonium chloride ide, NH , NH4 4Cl Cl
- 36. Some Ionic Compounds Some Ionic Compounds Mg Mg2+ 2+ + NO + NO3 3 - - ----> Mg(NO ----> Mg(NO3 3) )2 2 magnesium magnesium nitr nitrate ate Fe Fe2+ 2+ + PO + PO4 4 3- 3- ----> Fe ----> Fe3 3(PO (PO4 4) )2 2 iron(II) phosph iron(II) phosphate ate calcium fluor calcium fluoride ide Ca Ca2+ 2+ + 2 F + 2 F- - ---> ---> CaF CaF2 2
- 37. Properties of Ionic Compounds Properties of Ionic Compounds Forming NaCl from Na and Cl Forming NaCl from Na and Cl2 2 • A metal atom can A metal atom can transfer an transfer an electron to a electron to a nonmetal. nonmetal. • The resulting The resulting cation and anion cation and anion are attracted to are attracted to each other by each other by electrostatic electrostatic forces forces. .
- 38. Electrostatic Forces Electrostatic Forces The oppositely charged ions in ionic compounds are The oppositely charged ions in ionic compounds are attracted to one another by attracted to one another by ELECTROSTATIC ELECTROSTATIC FORCES FORCES. . These forces are governed by These forces are governed by COULOMB’S LAW COULOMB’S LAW. .
- 39. Electrostatic Forces Electrostatic Forces COULOMB’S LAW COULOMB’S LAW Force of attraction = (charge on +)(charge on -) (distance between ions)2 As ion charge increases, the attractive force As ion charge increases, the attractive force _______________. _______________. As the distance between ions increases, the As the distance between ions increases, the attractive force ________________. attractive force ________________. This idea is important and will come up This idea is important and will come up many times in future discussions! many times in future discussions!
- 40. Importance of Coulomb’s Law Importance of Coulomb’s Law NaCl, Na NaCl, Na+ + and Cl and Cl- - , , m.p. 804 m.p. 804 o o C C MgO, Mg MgO, Mg2+ 2+ and O and O2- 2- m.p. 2800 m.p. 2800 o o C C
- 41. ELEMENTS THAT EXIST AS ELEMENTS THAT EXIST AS MOLECULES MOLECULES See SCREEN 3.2 See SCREEN 3.2 on the CD-ROM on the CD-ROM Allotropes of C Allotropes of C
- 43. ELEMENTS THAT EXIST AS ELEMENTS THAT EXIST AS DIATOMIC DIATOMIC MOLECULES (gases) MOLECULES (gases)
- 44. ELEMENTS THAT EXIST AS ELEMENTS THAT EXIST AS POLYATOMIC POLYATOMIC MOLECULES MOLECULES White P4 and polymeric red phosphorus S8 sulfur molecules
- 45. Molecular Compounds Molecular Compounds Compounds without Ions Compounds without Ions CH4 methane CO2 Carbon dioxide BCl3 boron trichloride
- 46. Naming Molecular Naming Molecular Compounds Compounds CH4 methane BCl3 boron trichloride CO2 Carbon dioxide All are formed from two or more nonmetals. Ionic compounds generally involve a metal and nonmetal (NaCl)
- 47. Empirical & Molecular Empirical & Molecular Formulas Formulas A pure compound always consists of the A pure compound always consists of the same elements combined in the same same elements combined in the same proportions by weight. proportions by weight. Therefore, we can express molecular Therefore, we can express molecular composition as composition as PERCENT BY PERCENT BY WEIGHT WEIGHT Ethanol, C Ethanol, C2 2H H6 6O O 52.13% C 52.13% C 13.15% H 13.15% H 34.72% O 34.72% O
- 48. Percent Composition Percent Composition Consider some of the family of nitrogen- Consider some of the family of nitrogen- oxygen compounds: oxygen compounds: NO NO2 2, nitrogen dioxide and closely , nitrogen dioxide and closely related, NO, nitrogen monoxide (or related, NO, nitrogen monoxide (or nitric oxide) nitric oxide) Structure of NO Structure of NO2 2 Chemistry of NO, Chemistry of NO, nitrogen monoxide nitrogen monoxide
- 49. Percent Composition Percent Composition Consider NO Consider NO2 2, Molar mass = ? , Molar mass = ? What is the weight percent of N and of What is the weight percent of N and of O? O? Wt. % O 2 (16 .0 g O per mole ) 46 .0 g x 100 % 69 .6% Wt. % N = 14.0 g N 46.0 g NO2 • 100% = 30.4 % What are the weight percentages of What are the weight percentages of N and O in NO? N and O in NO?
- 50. How to Determine a Formula? How to Determine a Formula? Mass spectrometer Mass spectrometer
- 51. Mass Spectrum of Ethanol Mass Spectrum of Ethanol Mass Spectrum of Ethanol Mass Spectrum of Ethanol (from the NIST site) (from the NIST site) 46 45 CH3CH2OH+ CH3CH2O+ 31 CH2O+
- 52. Determining Formulas Determining Formulas In In chemical analysis chemical analysis we determine we determine the % by weight of each element in a given the % by weight of each element in a given amount of pure compound and derive the amount of pure compound and derive the EMPIRICAL EMPIRICAL or or SIMPLEST SIMPLEST formula. formula. PROBLEM PROBLEM: A compound of B and H : A compound of B and H is 81.10% B. What is its empirical is 81.10% B. What is its empirical formula? formula?
- 53. • Because it contains only B and H, it Because it contains only B and H, it must contain 18.90% H. must contain 18.90% H. • In 100.0 g of the compound there are In 100.0 g of the compound there are 81.10 g of B and 18.90 g of H. 81.10 g of B and 18.90 g of H. • Calculate the Calculate the number of moles number of moles of each of each constitutent. constitutent. A compound of B and H is 81.10% B. What is A compound of B and H is 81.10% B. What is its empirical formula? its empirical formula?
- 54. Calculate the Calculate the number of moles number of moles of each of each element in 100.0 g of sample. element in 100.0 g of sample. 81.10 g B • 1 mol 10.81 g = 7.502 mol B 18.90 g H • 1 mol 1.008 g = 18.75 mol H A compound of B and H is 81.10% B. What is A compound of B and H is 81.10% B. What is its empirical formula? its empirical formula?
- 55. Now, recognize that Now, recognize that atoms combine in the atoms combine in the ratio of small whole numbers. ratio of small whole numbers. 1 atom B + 3 atoms H --> 1 molecule BH 1 atom B + 3 atoms H --> 1 molecule BH3 3 or or 1 mol B atoms + 3 mol H atoms ---> 1 mol B atoms + 3 mol H atoms ---> 1 mol BH 1 mol BH3 3 molecules molecules Find the Find the ratio of moles ratio of moles of elements in of elements in the compound. the compound. A compound of B and H is 81.10% B. What is A compound of B and H is 81.10% B. What is its empirical formula? its empirical formula?
- 56. But we need a But we need a whole number ratio whole number ratio. . 2.5 mol H/1.0 mol B = 5 mol H to 2 mol B 2.5 mol H/1.0 mol B = 5 mol H to 2 mol B EMPIRICAL FORMULA = B EMPIRICAL FORMULA = B2 2H H5 5 Take the ratio of moles of B and H. Take the ratio of moles of B and H. Always Always divide by the smaller number. divide by the smaller number. 18.75 mol H 7.502 mol B = 2.499 mol H 1.000 mol B = 2.5 mol H 1.0 mol B A compound of B and H is 81.10% B. What is A compound of B and H is 81.10% B. What is its empirical formula? its empirical formula?
- 57. A compound of B and H is 81.10% B. A compound of B and H is 81.10% B. Its Its empirical formula empirical formula is B is B2 2H H5 5. What is . What is its its molecular formula molecular formula? ? Is the molecular formula B Is the molecular formula B2 2H H5 5, B , B4 4H H10 10, , B B6 6H H15 15, B , B8 8H H20 20, etc.? , etc.? B B2 2H H6 6 is one example of this class of compounds. is one example of this class of compounds. B2H6
- 58. A compound of B and H is 81.10% B. Its empirical A compound of B and H is 81.10% B. Its empirical formula is B formula is B2 2H H5 5. What is its molecular formula . What is its molecular formula? ? We need to do an We need to do an EXPERIMENT EXPERIMENT to find to find the MOLAR MASS. the MOLAR MASS. Here experiment gives Here experiment gives 53.3 g/mol 53.3 g/mol Compare with the mass of B Compare with the mass of B2 2H H5 5 = = 26.66 g/unit 26.66 g/unit Find the ratio of these masses. Find the ratio of these masses. 53.3 g/mol 26.66 g/unit of B2H5 = 2 units of B2H5 1 mol Molecular formula = B Molecular formula = B4 4H H10 10
- 59. Determine the formula of a Determine the formula of a compound of Sn and I using the compound of Sn and I using the following data. following data. • Reaction of Sn and I Reaction of Sn and I2 2 is done using excess Sn. is done using excess Sn. • Mass of Sn in the beginning = 1.056 g Mass of Sn in the beginning = 1.056 g • Mass of iodine (I Mass of iodine (I2 2) used = 1.947 g ) used = 1.947 g • Mass of Sn remaining Mass of Sn remaining = 0.601 g = 0.601 g
- 60. Find the Find the mass of Sn that combined mass of Sn that combined with with 1.947 g I 1.947 g I2 2. . Mass of Sn initially = 1.056 g Mass of Sn initially = 1.056 g Mass of Sn recovered = 0.601 g Mass of Sn recovered = 0.601 g Mass of Sn used = 0.455 g Mass of Sn used = 0.455 g Find Find moles of Sn used moles of Sn used: : 0.455 g Sn • 1 mol 118.7 g = 3.83 x 10-3 mol Sn Tin and Iodine Compound Tin and Iodine Compound
- 61. Tin and Iodine Compound Tin and Iodine Compound Now find the Now find the number of moles of I number of moles of I2 2 that that combined with 3.83 x 10 combined with 3.83 x 10-3 -3 mol Sn. Mass mol Sn. Mass of I of I2 2 used was 1.947 g. used was 1.947 g. 1.947 g I2 • 1 mol 253.81 g = 7.671 x 10-3 mol I2 How many mol of How many mol of iodine atoms iodine atoms? ? = 1.534 x 10-2 mol I atoms 7.671 x 10-3 mol I2 2 mol I atoms 1 mol I2
- 62. Tin and Iodine Compound Tin and Iodine Compound Now find the ratio of number of moles of moles Now find the ratio of number of moles of moles of I and Sn that combined. of I and Sn that combined. 1.534 x 10-2 mol I 3.83 x 10-3 mol Sn = 4.01 mol I 1.00 mol Sn Empirical formula is Empirical formula is SnI SnI4 4
Editor's Notes
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