CHEM-UP! D A Y 3-2013 The Academic Support Center @ Daytona State College (Chem-Up 3, Page 1 of 101)
Chapter 4 Lecture Basic Chemistry Chem Up! An Introduction to Basic Chemistry Concepts Day 3 Fourth Edition As you come in: 1. Sign in. 2. Write your name on a raffle ticket to leave at the front desk. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 2 of 101)
Welcome! Please introduce yourself to your neighbors. Some activities will require working in groups of two to three. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 3 of 101)
AGENDA FOR DAY 3 Bonds & Intermolecular Forces Study Skills Molecular Bonding Electronegativity & Polarity Intermolecular Bonding Solvency Attractive Forces The Academic Support Center @ Daytona State College (Chem-Up 3, Page 4 of 101)
SKILLS TO HELP YOU SUCCEED Before Class Course Expectations Using your Textbook Wisely During Class After Class Note taking Skills for Science Courses Active Class Participation Study Techniques Creating Study Aids Resources The Academic Support Center @ Daytona State College (Chem-Up 3, Page 5 of 101)
Course Structure How is my grade calculated? (How much are my labs, assignments, quizzes, and exams worth?) Example 1: Microbiology Lecture Portion (430 points) Exams (4) 100 pts each Final Exam 100 pts Written Assignment 30 pts Lab Portion (282 points) Lab Homework 52 pts Lab Quizzes 100 pts Unknown Lab 30 pts Lab Exam 100 pts Total: 712 pts The Academic Support Center @ Daytona State College (Chem-Up 3, Page 6 of 101)
Course Structure How is my grade calculated? (How much are my labs, assignments, quizzes, and exams worth?) Example 2: Biological Themes in Film Quizzes (best 8 of 11) 160 pts Tests (best 8 of 11) 360 pts Online Discussions 220 pts Using Correct Grammar 60 pts Total: 800 pts The Academic Support Center @ Daytona State College (Chem-Up 3, Page 7 of 101)
Course Structure How is my grade calculated? (How much are my labs, assignments, quizzes, and exams worth?) Example 3: Intro to Chemistry Quizzes 100 pts Tests 300 pts Lab 100 pts Homework 50 pts Final Exam 200 pts Total: 750 pts The Academic Support Center @ Daytona State College (Chem-Up 3, Page 8 of 101)
Course Structure Does it matter if I come to class? Many courses have attendance requirements. Some instructors may take off points for tardiness or absence. Will I be allowed to make up my labs, my homework, or my tests? Every instructor is different! This is an important thing to consider if you have unexpected conflicts come up during the semester. Am I expected to use proper grammar? Introductory science courses are college credit! It is expected that all communications (not just papers!) are written using proper grammar, punctuation, and spelling. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 9 of 101)
Course Structure What grade do I need to achieve? 90-100% A 70-76% C 87-89% B+ 67-69% D+ 80-86% B 60-66% D 77-79% C+ 59% and below F What textbook(s) do I need? When and where do I complete my homework or assignments? Where can I find the answers to these questions? Your course syllabus! The Academic Support Center @ Daytona State College (Chem-Up 3, Page 10 of 101)
Before Class.Using your Textbook Wisely I have to read every word. If I skim, my comprehension will drop. Some Myths about Reading Science Textbooks It is sinful to skip paragraphs or sections. Reading a chapter once is enough. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 11 of 101)
BEFORE CLASS. Preview the textbook Scan the introductory paragraph to determine any concepts you should have previously mastered. Review concepts from previous days that you were unclear about. Scan the chapter and look for main ideas and terminology that will be introduced in class. Pay special attention to headings, bolded words, diagrams, and figures. Mark concepts that look particularly difficult or any questions you may have. Make sure that you gain comprehension of these during class. Lecture Notes If your instructor posts PowerPoint lectures or notes before class preview these too! If you have previewed the text/lecture notes before class, then the material is familiar! The Academic Support Center @ Daytona State College (Chem-Up 3, Page 12 of 101)
DURING CLASS TAKING EFFECTIVE NOTES Read assigned material before class and bring a pen/pencil and highlighter. Always use the same notebook for your notes. Date each entry at the top of the page. If the instructor emphasizes a concept s importance or repeats it more than once, highlight that portion of your notes with your highlighter. Leave one to two blank lines after each topic. You can use this space to write additional examples from the textbook (including page numbers) or to summarize the notes in your own words. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 13 of 101)
Taking Effective Notes Place a question mark next to anything you don t understand. Ask the instructor or tutor for clarification, or look up the concept in the textbook. Helpful Resource Review your notes after class, within 24 hours if possible. Fill in any gaps. Rework sample problems on a separate paper and then compare your answer to the original. Your instructor is a great resource. They often don t have students utilize their office hours, so feel free to stop by and ask them to clarify any gaps you may have in your notes. Recording the lecture may be helpful! The Academic Support Center @ Daytona State College (Chem-Up 3, Page 14 of 101)
Some Examples The Academic Support Center @ Daytona State College (Chem-Up 3, Page 15 of 101)
Some Examples The Academic Support Center @ Daytona State College (Chem-Up 3, Page 16 of 101)
Some Examples The Academic Support Center @ Daytona State College (Chem-Up 3, Page 17 of 101)
Some Examples The Academic Support Center @ Daytona State College (Chem-Up 3, Page 18 of 101)
Properties of Solids and Liquids 1) Electron-Dot Formulas Learning Goal Draw the electron-dot formulas for molecular compounds or polyatomic ions with multiple bonds and show resonance structures. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 19 of 101)
Electron-Dot Symbols Electron-dot symbols show one to four valence electrons as single dots on the sides of an atomic symbol five to eight valence electrons with one or more pairs of dots on the sides of an atomic symbol The Academic Support Center @ Daytona State College (Chem-Up 3, Page 20 of 101)
Electron-Dot Symbols of Some Representative Elements The Academic Support Center @ Daytona State College (Chem-Up 3, Page 21 of 101)
Electron-Dot Formulas Electron-dot formulas show the sequence of bonded atoms in a molecule or polyatomic ion the bonding pairs of electrons shared between atoms the nonbonding or unshared (lone pairs) of electrons the central atom bonded to other atoms The Academic Support Center @ Daytona State College (Chem-Up 3, Page 22 of 101)
Lone Pairs and Bonding Pairs The electron-dot formula for H 2 O contains: 8 valence electrons (6 from O plus 1 from each hydrogen atom) O as the central atom two bonding pairs (between the H and O atoms) and two lone pairs (on the O atom) H O H The Academic Support Center @ Daytona State College (Chem-Up 3, Page 23 of 101)
Drawing Electron-Dot Formulas The Academic Support Center @ Daytona State College (Chem-Up 3, Page 24 of 101)
Writing Electron-Dot Formulas Draw the electron-dot formula for PCl 3, phosphorus trichloride, used to prepare insecticides and flame retardants. Step 1 Determine the arrangement of atoms. The central atom is P; there is only one P atom. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 25 of 101)
Writing Electron-Dot Formulas Draw the electron-dot formula for PCl 3. Step 2 Determine the total number of valence electrons. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 26 of 101)
Writing Electron-Dot Formulas Draw the electron-dot formula for PCl 3. Step 3 Attach each bonded atom to the central atom with a pair of electrons. Bonding electrons can also be represented by a line. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 27 of 101)
Writing Electron-Dot Formulas Draw the electron-dot formula for PCl 3. Step 4 Place the remaining electrons using single or multiple bonds to complete the octets. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 28 of 101)
Writing Electron-Dot Formulas Draw the electron-dot formula for PCl 3. Step 4 Place the remaining electrons using single or multiple bonds to complete the octets. Use the remaining 20 e as lone pairs on P and Cl atoms to complete octets. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 29 of 101)
Molecular Bonding 2) Ionic, Single, Double, and Triple Bonds Learning Goal Introduction to common bonds found in molecules and the octet rule. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 30 of 101)
Ionic and Molecular Compounds The Academic Support Center @ Daytona State College (Chem-Up 3, Page 31 of 101)
Multiple Bonds Multiple bonds form when there are not enough valence electrons to complete octets. In a single bond, one pair of electrons is shared. In a double bond, two pairs of electrons are shared. In a triple bond, three pairs of electrons are shared. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 32 of 101)
Multiple Bonds, CO 2 In carbon dioxide, CO 2, octets are achieved by sharing two pairs of electrons between atoms; this is called a double bond. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 33 of 101)
Multiple Bonds, N 2 In nitrogen, N 2, octets are achieved by sharing three pairs of electrons between atoms; this is called a triple bond. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 34 of 101)
Exceptions to the Octet Rule Exceptions to the octet rule include: hydrogen, H, only gets a single bond boron, B, has only 3 electrons around it to form bonds compounds of P, S, Cl, Br, and I can have expanded octets with 10, 12, or even 14 valence electrons around them The Academic Support Center @ Daytona State College (Chem-Up 3, Page 35 of 101)
Using Valence Electrons to Draw Electron- Dot Formulas The Academic Support Center @ Daytona State College (Chem-Up 3, Page 36 of 101)
Time For Lesson 7 Lewis Dot Structures The Academic Support Center @ Daytona State College (Chem-Up 3, Page 37 of 101)
Properties of Solids and Liquids 3) Shapes of Molecules and Ions (VSEPR Theory) Learning Goal Predict the threedimensional structure of a molecule or a polyatomic ion and classify it as polar or nonpolar. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 38 of 101)
VSEPR In the valence shell electron repulsion theory (VSEPR), the three-dimensional shape of a molecule is determined by drawing the electron-dot formula counting the number of electron groups (one or more electron pairs) around the central atom placing the electron groups as far apart as possible around the central atom number of electron groups surrounding the central atom number of atoms bonded to the central atom The Academic Support Center @ Daytona State College (Chem-Up 3, Page 39 of 101)
Molecular Shapes The Academic Support Center @ Daytona State College (Chem-Up 3, Page 40 of 101)
Molecular Shapes The Academic Support Center @ Daytona State College (Chem-Up 3, Page 41 of 101)
Guide to Predicting Molecular Shape (VSEPR Theory) The Academic Support Center @ Daytona State College (Chem-Up 3, Page 42 of 101)
Learning Check Use VSEPR theory to predict the shape of N 2 O. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 43 of 101)
Solution Use VSEPR theory to predict the shape of N 2 O. Step 1 Draw the electron-dot formula. In the electron-dot structure with 16 e, octets are acquired using two double bonds in the central N atom. N N O The Academic Support Center @ Daytona State College (Chem-Up 3, Page 44 of 101)
Solution Use VSEPR theory to predict the shape of N 2 O. Step 2 Arrange the electron groups around the central atom to minimize repulsion. Repulsion is minimized with two electron groups at 180, a linear arrangement. N N O The Academic Support Center @ Daytona State College (Chem-Up 3, Page 45 of 101)
Solution Use VSEPR theory to predict the shape of N 2 O. Step 3 Use the atoms bonded to the central atom to determine the molecular shape. The shape of a N 2 O molecule with two bonded atoms and no lone pairs on the central N is linear. N N O The Academic Support Center @ Daytona State College (Chem-Up 3, Page 46 of 101)
Learning Check State the number of electron groups, lone pairs, and bonded atoms, and use VSEPR theory to determine the shape of the following molecules: (a) tetrahedral (b) trigonal pyramidal (c) bent 1. PF 3 2. H 2 S 3. CCl 4 4. PO 4 3 The Academic Support Center @ Daytona State College (Chem-Up 3, Page 47 of 101)
Solution State the number of electron groups, lone pairs, and bonded atoms, and use VSEPR theory to determine the shape of the following molecules: (a) tetrahedral (b) trigonal pyramidal (c) bent 1. PF 3 4 electron groups, 3 bonded atoms, 1 lone pair, trigonal pyramidal (b) 2. H 2 S 4 electron groups, 2 bonded atoms, 2 lone pairs, bent (c) The Academic Support Center @ Daytona State College (Chem-Up 3, Page 48 of 101)
Solution State the number of electron groups, lone pairs, and bonded atoms, and use VSEPR theory to determine the shape of the following molecules: (a) tetrahedral (b) trigonal pyramidal (c) bent 3. CCl 4 4 electron groups, 4 bonded atoms, 0 lone pairs, tetrahedral (a) 4. PO 4 3 4 electron groups, 4 bonded atoms, 0 lone pairs, tetrahedral (a) The Academic Support Center @ Daytona State College (Chem-Up 3, Page 49 of 101)
Time For Lesson 8 Molecular Shape The Academic Support Center @ Daytona State College (Chem-Up 3, Page 50 of 101)
Properties of Solids and Liquids 4) Electronegativity and Polarity Learning Goal Use electronegativity to determine the polarity of a bond or a molecule. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 51 of 101)
Electronegativity and Polarity We can learn more about the chemistry of compounds by understanding how electrons are shared in bonds. Bonds formed by identical atoms share the bonding electrons equally. Bonds formed between different atoms share the bonding electrons unequally. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 52 of 101)
Electronegativity Electronegativity is the relative ability of atoms to attract shared electrons is higher for nonmetals; fluorine (F) has the highest with a value of 4.0 is lower for metals; cesium (Cs) and francium (Fr) have the lowest value of 0.7 The Academic Support Center @ Daytona State College (Chem-Up 3, Page 53 of 101)
Electronegativity We can use the periodic table to predict the relative electronegativity value for each element. Electronegativity increases from left to right going across a period on the periodic table decreases going down a group on the periodic table The Academic Support Center @ Daytona State College (Chem-Up 3, Page 54 of 101)
Electronegativity Figure 10.1 The electronegativity values of the representative elements in Group 1A (1) to Group 7A (17), which indicate the ability of atoms to attract shared electrons, increase going across a period from left to right and decrease going down a group. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 55 of 101)
Learning Check Using the periodic table, predict the order of increasing electronegativity for the elements O, K, and C. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 56 of 101)
Solution Using the periodic table, predict the order of increasing electronegativity for the elements O, K, and C. Answer: K, C, O K, period 4, group 1A (1), has an electronegativity value of 0.8. C, period 2, group 4A (14), has an electronegativity value of 2.5. O, period 2, group 6A (16), has an electronegativity value of 3.5. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 57 of 101)
Intermolecular Bonding 5) Covalent Bonds, Nonpolar Covalent Bonds, Dipoles, and Bond Polarity Learning Goal Introduction various intermolecular bonds. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 58 of 101)
Covalent Bonding Video The Academic Support Center @ Daytona State College (Chem-Up 3, Page 59 of 101)
Types of Covalent Bonds Bonds can be described by the difference in the electronegativity of the bonding atoms. Two types of covalent bonds occur in molecules: nonpolar covalent bonds; bonding electrons are shared equally polar covalent bonds; bonding electrons are shared unequally The Academic Support Center @ Daytona State College (Chem-Up 3, Page 60 of 101)
Nonpolar Covalent Bonds A nonpolar covalent bond between nonmetal atoms consists of an equal (or almost equal) sharing of electrons has a zero (or close to zero) electronegativity difference (0.0 to 0.4) The Academic Support Center @ Daytona State College (Chem-Up 3, Page 61 of 101)
Polar Covalent Bonds A polar covalent bond between nonmetal atoms consists of an unequal sharing of electrons has an electronegativity difference of 0.5 to 1.7 The Academic Support Center @ Daytona State College (Chem-Up 3, Page 62 of 101)
Polar and Nonpolar Covalent Bonds Figure 10.2 In the nonpolar covalent bond of H 2, electrons are shared equally. In the polar covalent bond of HCl, electrons are shared unequally. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 63 of 101)
Dipoles and Bond Polarity Bonds become more polar as the difference in electronegativity increases. A polar covalent bond that has a separation of charges is called a dipole. The positive and negative ends are represented by the Greek letter delta, with a + or charge. Arrows can also be used to represent dipoles. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 64 of 101)
Electronegativity and Types of Bonds Variations in bonding are continuous. Bonds with an electronegativity difference of 0.0 0.4 are considered nonpolar. Bonds with an electronegativity difference of 0.5 1.7 are considered polar covalent. Bonds with an electronegativity difference greater than 1.8 are considered ionic. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 65 of 101)
Electronegativity Video The Academic Support Center @ Daytona State College (Chem-Up 3, Page 66 of 101)
Predicting Bond Type The Academic Support Center @ Daytona State College (Chem-Up 3, Page 67 of 101)
Learning Check Complete the following table for each of the bonds indicated. Bond Si - S Cs - Cl Cl - Cl Si - P Electronegativity Difference Type of Bond The Academic Support Center @ Daytona State College (Chem-Up 3, Page 68 of 101)
Solution Complete the following table for each of the bonds indicated. Bond Electronegativity Type of Bond Difference Si - S 2.5 1.8 = 0.7 Polar Covalent Cs - Cl 3.0 0.7 = 2.3 Ionic Cl - Cl 0 Nonpolar Covalent Si - P 2.1 1.8 = 0.3 Nonpolar Covalent The Academic Support Center @ Daytona State College (Chem-Up 3, Page 69 of 101)
Polarity of Molecules Nonpolar In a nonpolar molecule, all the bonds are nonpolar, or the polar bonds (dipoles) cancel each other out. Molecules such as H 2, Cl 2 and CH 4 are nonpolar because they contain only nonpolar bonds. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 70 of 101)
Polarity of Molecules Nonpolar A nonpolar molecule also occurs when polar bonds (dipoles) cancel each other because of a symmetrical arrangement. Molecules such as CO 2 and CCl 4 contain polar bonds with dipoles that cancel each other out. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 71 of 101)
Polarity of Molecules Polar A polar molecule occurs when the dipoles from individual bonds do not cancel each other out. For molecules with two or more electron groups, the shape (such as bent or trigonal pyrimidal) determines whether or not the dipoles cancel. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 72 of 101)
Polarity of Molecules Polar Examples of polar molecules include HCl, H 2 O, and NH 3. HCl is linear and contains a polar bond. H 2 O is bent and contains two polar bonds as well as two lone pairs on oxygen. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 73 of 101)
Guide to Determination of Polarity of a Molecule The Academic Support Center @ Daytona State College (Chem-Up 3, Page 74 of 101)
Solvency Solvency - ability to dissolve other chemicals o Hydrophilic (charged, ionic or polar substances) dissolve easily in water salt o Hydrophobic (neutral or non-polar substances) do not easily dissolve in water oil Water = universal solvent The Academic Support Center @ Daytona State College (Chem-Up 3, Page 75 of 101)
Learning Check Determine if the molecule OF 2 is polar or nonpolar. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 76 of 101)
Solution Determine if the molecule OF 2 is polar or nonpolar. Step 1 Determine if the bonds are polar or nonpolar covalent. Oxygen has an electronegativity of 3.5, and fluorine has an electronegativity of 4.0. O F bonds are polar covalent. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 77 of 101)
Solution Determine if the molecule OF 2 is polar or nonpolar. Step 2 If the bonds are polar covalent, draw the electron-dot formula and determine if the dipoles cancel. Dipoles in O F bonds do not cancel; the molecule is polar. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 78 of 101)
Time For Lesson 9 Polarity The Academic Support Center @ Daytona State College (Chem-Up 3, Page 79 of 101)
Properties of Solids and Liquids 6) Attractive Forces in Compounds Learning Goal Describe the attractive forces between ions, polar covalent molecules, and nonpolar covalent molecules. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 80 of 101)
Attractive Forces in Compounds Attractive forces between molecules and ions hold them close together in liquids and solids. Solids melt, and liquids boil when the attractive forces between molecules are broken. Attractive forces between molecules can be dipole dipole attractions hydrogen bonding dispersion forces The Academic Support Center @ Daytona State College (Chem-Up 3, Page 81 of 101)
Dipole-Dipole Attractions Polar molecules are attracted to each other by dipole-dipole attractions when the positive end of one dipole is attracted to the negative end of a second dipole such as the attractive forces between two molecules of H Cl The Academic Support Center @ Daytona State College (Chem-Up 3, Page 82 of 101)
Hydrogen Bonds Hydrogen bonds, especially strong dipoledipole attractions, occur between polar molecules containing hydrogen atoms bonded to very electronegative atoms such as fluorine (F), nitrogen (N), and oxygen (O) a hydrogen atom with a partial positive charge attached to N, O, or F and a partial negative charge on N, O, or F The Academic Support Center @ Daytona State College (Chem-Up 3, Page 83 of 101)
Chemistry Link to Health In a higher level structure of proteins, hydrogen bonds are formed to fold the proteins into different shapes, such as an alpha helix. -more on proteins on day 4 The Academic Support Center @ Daytona State College (Chem-Up 3, Page 84 of 101)
Dispersion Forces Dispersion forces, very weak attractive forces that occur between nonpolar molecules, occur when movement induces a temporary distortion of the electrons in a molecule, creating a temporary dipole make it possible for nonpolar molecules to exist as liquids and solids The Academic Support Center @ Daytona State College (Chem-Up 3, Page 85 of 101)
Bonding and Attractive Forces The Academic Support Center @ Daytona State College (Chem-Up 3, Page 86 of 101)
Learning Check Indicate the major type of molecular interaction such as dipole-dipole attractions, hydrogen bonds, or dispersion forces expected between each of the following: 1. NF 3 2. Cl 2 3. HF The Academic Support Center @ Daytona State College (Chem-Up 3, Page 87 of 101)
Solution Indicate the major type of molecular interaction such as dipole-dipole attractions, hydrogen bonds, or dispersion forces expected between molecules of: 1. NF 3 dipole-dipole attractions 2. Cl 2 dispersion forces 3. HF hydrogen bonds The Academic Support Center @ Daytona State College (Chem-Up 3, Page 88 of 101)
Size, Mass, and Boiling Points As the size and mass of similar types of molecules increase, the attractive forces between the molecules also increase there are more electrons available to produce stronger temporary dipoles These increased attractive forces increase the boiling points of these molecules. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 89 of 101)
Molar Mass and Boiling Points The Academic Support Center @ Daytona State College (Chem-Up 3, Page 90 of 101)
Attractive Forces and Melting Points The melting point of a substance is related to the strength of the attractive forces between its particles. Molecules with weaker dispersion forces have lower melting points; it takes less energy to break the dispersion forces stronger dipole-dipole forces, or hydrogen bonds, require more energy to break the forces between them The Academic Support Center @ Daytona State College (Chem-Up 3, Page 91 of 101)
Highest Melting Points The highest melting points occur in ionic compounds that have very strong attractive forces between positive and negative ions. Ionic compounds require large amounts of energy to break these forces and melt the substance. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 92 of 101)
Melting Points of Selected Substances The Academic Support Center @ Daytona State College (Chem-Up 3, Page 93 of 101)
Learning Check Identify the compound in each pair that has the higher melting point. Explain. A. NCl 3 or NH 3 B. HBr or Br 2 C. KCl or HCl The Academic Support Center @ Daytona State College (Chem-Up 3, Page 94 of 101)
Solution Identify the compound in each pair that has the higher melting point. Explain. A. NCl 3 or NH 3 NH 3 has a higher melting point than NCl 3 because the hydrogen bonds in NH 3 are stronger than the dipole-dipole attractions in NCl 3. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 95 of 101)
Solution Identify the compound in each pair that has the higher melting point. Explain. B. HBr or Br 2 HBr would have a higher melting point than Br 2 because the dipole-dipole attractions in HBr are stronger than the dispersion forces in Br 2. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 96 of 101)
Solution Identify the compound in each pair that has the higher melting point. Explain. C. KCl or HCl KCl would have a higher melting point than HCl because the ionic bonds in KCl are stronger than the dipole-dipole attractions in HCl. The Academic Support Center @ Daytona State College (Chem-Up 3, Page 97 of 101)
Concept Check The Academic Support Center @ Daytona State College (Chem-Up 3, Page 98 of 101)
Time For Lesson 10 Intermolecular Forces The Academic Support Center @ Daytona State College (Chem-Up 3, Page 99 of 101)
SNEAK PEEK AGENDA FOR DAY 4 Reactions & Molecules More Study Skills Chemical Reactions & Equations Acids & Bases Organic Compounds Molecules of Life The Academic Support Center @ Daytona State College (Chem-Up 3, Page 100 of 101)
Questions Compiled by J. Picione (Chemistry Faculty) D. Leonard, R. Wendt, J. Brown, E. Scott, and A. Kandefer (Learning Specialists) The Academic Support Center @ Daytona State College http://www.daytonastate.edu/asc/ascsciencehandouts.html The Academic Support Center @ Daytona State College (Chem-Up 3, Page 101 of 101)