General Chemistry I

General Chemistry II

Physical Chemistry II

9.15 A pair of electrons that is shared between two atoms is called a bonding pair, while a pair of electrons that is associated with only one atom—and therefore, not involved in bonding—is called a lone pair. 9.17 Generally, combinations of atoms that can satisfy the octet rule on each atom are stable, while those combinations that do not satisfy the octet rule are not stable. 9.19 Electronegativity is the ability of an atom to attract electrons to itself in a chemical bond. This results in a polar bond. Electronegativity generally increases across a period in the periodic table. And electronegativity gen- erally decreases down a column (group) in the periodic table. The most electronegative element is fluorine. 9.21 Percent ionic character is defined as the ratio of a bond’s actual dipole moment to the dipole moment it would have if the electron were completely transferred from one atom to the other, multiplied by 100. A bond in which an electron is completely transferred from one atom to another would have 100% ionic char- acter. However, no bond is 100% ionic. Percent ionic character generally increases as the electronegativity dif- ference increases. In general, bonds with greater than 50% ionic character are referred to as ionic bonds. 9.23 To calculate the dipole moment we use μ = qr : For 100 pm: For 200 pm: 9.25 The total number of electrons for a Lewis structure of a molecule is the sum of the valence electrons of each atom in the molecule. The total number of electrons for the Lewis structure of an ion is found by summing the number of valence electrons for each atom and then subtracting one electron for each positive charge or adding one electron for each negative charge. 9.27 In some cases we can write resonance structures that are not equivalent. One possible resonance structure may be somewhat better than another. In such cases the true structure may still be represented as an aver- age of the resonance structures, but with the better resonance structure contributing more to the true struc- ture. Multiple nonequivalent resonance structures may be weighted differently in their contributions to the true overall structure of a molecule. 9.29 The octet rule has some exceptions because not all atoms always have eight electrons surrounding them. The two major categories are 1) odd octets—electron species, molecules, or ions with an odd number of elec- trons, for example, NO, and 2) incomplete octets—molecules or ions with fewer than eight electrons around an atom, for example, BF 3 . 9.31 The bond energy of a chemical bond is the energy required to break 1 mol of the bond in the gas phase. Since breaking bonds is endothermic and forming bonds is exothermic we can calculate the overall enthalpy change as a sum of the enthalpy changes associated with breaking the required bonds in the reactants and forming the required bonds in the products. 9.33 When metal atoms bond together to form a solid, each metal atom donates one or more electrons to an electron sea. Problems by Topic Valence Electrons and Dot Structures 9.35 N : 1 s 2 2 s 2 2 p 3 The electrons included in the Lewis structure are 2 s 2 2 p 3 . 9.37 (a) Al: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 1 m = 1 .6 x 10 - 19 C x 200 pm x m 10 12 pm x D 3 .34 x 10 - 30 C # m = 9 .6 D m = 1 .6 x 10 - 19 C x 100 pm x m 10 12 pm x D 3 .34 x 10 - 30 C # m = 4 .8 D 158 Chapter 9 Chemical Bonding I: Lewis Theory

CHY | 113 | General Chemistry II | study guides | 9.15 A pair of electrons that 

amount of energy would be given oﬀ in the reverse reacon (Si + + e -  Si, ΔH° < 0). The electron aﬃnity of Si + should be the largest because it is a caon and will aract the electron the greatest. Note: According to eﬀecve nuclear charge, you would expect Si + to have the largest electron aﬃnity because it has the largest eﬀecve nuclear charge. According to electron conﬁguraons, you would expect Si to have the greatest electron aﬃnity because it has two unpaired electrons in its 3p subshell, and adding one more electron would create a half-ﬁlled subshell which is thermodynamically favourable. (Award 1 mark for either of these answers. They do not provide a complete explanaon.) Problem 3 (6 marks) Consider the reacon: A(aq)  B(aq) Δ r G° = -42.5 kJ mol -1 Under certain non-standard condions , the Gibbs energy change (Δ r G) for this reacon is found to be 0 kJ mol -1 . For each of the following statements, decide whether the statement is true or false, and jusfy your answer. (a) (2 marks) Under these non-standard condions, the reacon is at equilibrium. True. If the Gibbs energy (Δ r G) is zero, then the reacon is at equilibrium. (b) (2 marks) Under these non-standard condions, [A] = [B] = 1 mol L -1 . False. If the concentraon of reactants and products is 1 mol L -1 , then this is standard condions, and the Gibbs energy change under standard condions is -42.5 kJ mol -1 , not 0. (c) (2 marks) Under these non-standard standard condions, [B] > [A]. True. Method A: Jusﬁcaon using math Δ r G = Δ r G° + RTlnQ 0 = -42.5 + RTln([B]/[A]) ln([B]/[A]) = 42.5/(RT) > 0 (since R and T are both posive) Then [B]/[A] > e 0 = 1 And [B] > [A] Method B: Jusﬁcaon using math & words Δ r G° = -RTlnK Since Δ r G° is negave, K must be a large number, greater than 1. (For example, at 298 K, K = 2.8 x 10 7 . We did not specify a temperature in this queson, but any temperature above absolute zero would result in a K larger than 1.) In other words, at equilibrium, the reacon mixture contains mostly products and very lile reactants. This reacon mixture IS at equilibrium (see part a). So it contains mostly products (B) and very lile reactants (A), or [B] > [A].

CHY | 113 | General Chemistry II | exam | amount of energy would be give

1 Dr. Sharonna Greenberg sharonna.greenberg@ryerson.ca Tuesdays 3:00pm-4:00pm DSQ10 Fridays 9:00am-11:00am, DSQ23 CHY113 General Chemistry II 2 2 About Me  Love chemistry since the age of 3!  B.Sc. in Mathematics & Chemistry, University of Toronto  Ph.D. in Chemistry, University of Toronto 3 3 Ground Rules  Treat everyone with respect.  No question is a stupid question.  If you have to come late or leave early, enter/leave the room as quickly and quietly as possible. 4 4 Ground Rules  During the lecture, no social media: turn oﬀ your cell phones, facebook, twitter, etc.  Please tell me what you ﬁnd confusing and I can help you.  These Ground Rules can be expanded/modiﬁed at any time! 5 5 How to Reach Me  Email: sharonna.greenberg@ryerson.ca  Include CHY113 in the subject line.  I will usually reply within 24 h, not including weekends.  Oﬃce hours in VIC701:  Wednesdays 12:30 – 2:00pm  Fridays 1:30 – 2:30pm  By appointment: email me and attach a copy of your schedule then I will select a day & time in my response. 6 6 How to Reach You  All students are required to activate and maintain their Ryerson online identity at www.ryerson.ca/accounts  Regularly access Ryerson’s email (Rmail), RAMSS, my.ryerson.ca portal and learning system, and other systems to receive oﬃcial University communication. 7 Lectures  12 weeks, 9 textbook chapters, 1 test, 1 ﬁnal exam, labs  Topics include:  Thermodynamics  Quantum Mechanics  Periodic Properties  Bonding  Kinetics  Electrochemistry  Liquids & Solids  Lecture notes will be posted online at least 24 h beforehand 8 Supplies  Textbook  Mastering Chemistry – you must register by Jan 22 2016!  A non-programmable, non-communicable calculator. (You may NOT use your phone or any communicable device as a calculator on any test or exam.)  See the course outline for more details. What You Should Bring Every Class + extra batteries! 10 10 Important Dates & Marks  Lecture component – 70%  Mastering Chemistry – throughout the term – 8%  Clickers – throughout the term – 5%  Concept Inventory participation – week 2 – 1%  Midterm test – Friday March 4 – 24%  Final exam – April 16-30 – 32%  Laboratory component – 30%  You must pass both the lecture and the lab in order to pass the course! 11 11 Missed Evaluations  Contact your instructor immediately via e-mail/phone, preferably BEFORE and at the latest on the SAME DAY as the missed evaluation.  Submit a medical certiﬁcate AND and academic consideration form to the First Year and Common Science Oﬃce (FYCSO, VIC 743) within 3 business days.  Ensure all documentation is date-stamped by the oﬃce staﬀ.  If the documentation is acceptable, a makeup test will be scheduled on a Monday morning at 7am.  Read our course outline (posted under Content) for more details.

CHY | 113 | General Chemistry II | lecture notes | 1 Dr. Sharonna Greenberg sharo

1 General Chemistry Chapter 4: Chemical Reactions and Stoichiometry Lecture 1 of 4 $ Balancing Chemical Equations $ Ionic Solutions $ Solubility of Ionic Compounds $ Net Ionic Equations $ Types of Chemical Reactions $ Precipitation $ Acid-base 2 Balancing Chemical Equations The only useful chemical equation is a A balanced equation @ , i.e. one which has t

CHY | 103 | General Chemistry I | lecture notes | 1 General Chemistry Chapter 4:

2010_CHY_103_Midterm_2.pdf-eW ct!'l i,:.7 {i , T

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