Chemistry 1027A/B Lecture Notes - Lecture 1: Lone Pair, Chemical Polarity, Lewis Structure

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15 Mar 2015

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Properties of molecules entirely dependent on the arrangement of valence electrons. Chemical structures only drawn with valence electrons (dots around atoms) Electrons seem to be share not the case because in electronegativity (greater 1. 9) Complete transfer of electrons from the atom of lower electronegativity to one with higher electronegativity. Attractive coulombic forces between anions and cations crystal lattice forms in solid state. Single cation is attracted to several anions and vice versa. Strong forces account for high melting points of ionic compounds. K proportionality constant known as coulomb"s law constant. Compounds that involve smaller ions tend to have larger forces and higher melting points. Involve sharing of electrons sharing is not always equal. Polar bond dipole moment: uneven distribution of charge due to electronegativity different results in a. Diagrammatic representation of a molecule that show covalent bonds, paired and unpaired electrons and any charges. Lewis structures contain atom with positive and negative charges (formal)

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How do you answer 1-4?

Physical Constants R-00821 L.atm rnol. K: 1 atm = 760 Torr; h-6626 x 10". Js; c-3.00 x 10e mis Multiple Choice Question-4 points each. Circle the correct choice. 1. How many orbitals are there in the n - 3 shell? )3 b)6 )9 d) 12 e) none of the preceding choices 2. Which of the following is not a valid set of four quantum numbers to describe an electron in an atom? 3. Which pair of elements would you expect to exhibit the most similar physical and chemical properties? a) As and Se b) Na and Cl c) As and Sb d) B and Be 4) The number of unpaired electrons in the ground state of an atom of Co is.. (A) one (B) three (C) five (D) seven (E) none of the preceding choices S. Which of the following processes is exothermic? a) lonization of a sodium atom b) Formation of gaseous chlorine atoms from Cl, (g) c) Breaking apart of NaC1 (s) into ions d)Addition of an electron to a chlorine atom 6. Which of the following bonds is the most polar? a) N-O b)O-F e) B-O d)S-o e) all are equally polar At what temperature (in C) will 25.0 g of carbon dioxide (at 1,00 atm) occupy 21.5 L? 188Â°C b) 461Â°C c) -263Â°C d)-270Â°C e)113Â°C How many times more rapidly will hydrogen (H2) gas effuse through a pinhole than will deuterium (D ) gas? Deuterium is an isotope of hydrogen with a molecular mass of 4.0 g/mole. (A) V2 (B) 2 (C)2v2 (D) 4 9. Which of the following arrangements from lowest to highest in first ionization energies is correct ? 10. In which of the following compounds obeys the octet rule? 1. The bright spectral lines observed in the emission spectrum of a flame or gas discharge tube are due to a) XeF b) BF, c) Cio d) so e) none of the preceding choicees a) the absorption of light at specific wavelengths b) the formation of an excited state of atoms c) the transition of an atom from an excited state to a lower energy state d) the change from anti-parallel to parallel electron spins in an atom 2. A one-liter container is filled with one mole of hydrogen at 25 Â°C. A second one-liter container is filled with one mole f oxygen at 25 Â°C. Comparing the pressure of the hydrogen to the oxygen, the ratio will be Fro n Bond Dissociation Enthalpies: AHD (CI-CI)-243 kJrnolAMD (F-F )ä¸159 klinol; lculate the enthalpy, AH, for the chemical reaction: Cl: (g)+F: (g) 2CIF(R) )-147 kJ (b)-108 kJ (c)+171 kJ (d) +912 k AHD (CI F)-255 kJ mol ;

How do you solve #8?

Brooklyn College of C.U.N.Y Spring 209 Chemistry 1.2 Makeup Midterm Exam Lab. Sectio Physical Constants R-0.0821 L.atrn /mM1 K: 1 atrm-760 Torr; h-6.626 x 10" Js. c-300 x 10' mis Multiple Choice Question4 points each. Circle the correct choice I. How many orbitals are there in the n - 3 shel 2. Which of the following is not a valid set of four b6 ( 4)12 e) none of the preceding choices quantum numbers to describe an electron in an atom? 3. Which pair of elements would you expect to exhibit the most similar physical and chemical peoperties? a) As and Se Na and ci As and Sb s) B and Bensnp 4) The rn unpaired electrons in the ground state of an atom of Co is... ree (C) five (D) seven (E) none of the preceding choices 0è®ä¸ä½å£ wch of the following processes is exothermic? a) lonization of a sodium atom b) Formation of gaseous Which of the following bonds is the most polar? a) N-O b)o-F ) B-o )so e)all are equally polar t what temperature (in C) will 25.0 g of carbon dioxide (at 1.00 atm) occupy 21.3 L? 8Â°C b) 461 C c) -263Â°C d)-270Â°C e) 113Â°C How many times more rapidly will hydrogen (H,) gas effuse through a pinhole than will deuterium ( Deuterium is an isotope of hydrogen with a molecular mass of 4.0 g'mole. (A) 2 (B)2 (C)2v2 (D)4 9, Which of the following arrangements from lowest to highest in first ionization energies is correct ? 10. In which of the following compounds obeys the octet rule? a) XeF b) BF, c) CIO d) SO, pone of the preceding choicees 11. The bright spectral lines observed in the emission spectrum of a flame or gas discharge tube are due to a) the absorption of light at specific wavelengths b) the formation of an excited state of atoms the transition of an atom from an excited state to a lower energy state d) the change from anti-parallel to parallel electron spins in an atom oxygen at 25 Â°C. Comparing the pressure of the hydrogen to the exygen, the ratio will be From Bond Dissociation Enthalpies: Î11D (CI-CI)-243 klinolalo (F-F )-159 kJ/mol; Î1lo (CHF)-25 12.A one-liter container is filled with one mole of hydrogen at 25 Â°C.A second one-liter container is filled with or 2CIF(R) alculate the enthalpy, AH, for the chemical reaction: Cl (g)+ F: (g) (a)-147 kJ (b)-108 kJ (c) +171 kJ (d) +912J (H lou, mory t,hes more rapidy wil, hydrogen w many tes more ro

Practice problems for exam 2 ______________

Useful Information:

h=6.626Ã10-34JÂ·s.; c=3.0Ã108 m/sec; E=hï® ; E= hc , ï¬ = h/mv; 1J = 1 kg-m2/s2 ï¬

mass of electron = 9.11 Ã 10-28 g, ïE= q + w ; 1 cal = 4.184 Joules Please Show all Work

1. Which of the following substances have standard heats of formation that are equal to zero by definition (circle your answers): H2(g), H(g), O3(g), H2O(s), H2O(l), Hg(l), Hg(s), Hg(g).

2. Limestone stalactites are formed in the reaction: Ca2+(aq) + HCO3-(aq) ï CaCO3(s) + CO2(g) +

H2O(l)
If one mole of CaCO3 is produced at 298 K under one atmosphere of pressure, the reaction performs 590 calories of expansion work, pushing back the atmosphere as CO2 is formed. At the same time, 9310 calories of heat are absorbed from the environment. What is ïE in Kcal/mole for CaCO3.

3. What is the minimum wavelength of light in AÌ (1 AÌ = 10-8 cm) needed to provide enough energy per quantum to rupture the chemical bond in hydrogen iodide (HI). The bond dissociation energy of HI is 71.4 Kcal/mole.

4. Sketch the shape and orientation of the following types of orbitals: s, px, dxy, dz2, dx2-y2

5. Give the values of (n) , (l) and (ml) for each orbital in the 4p subshell.

6. Write the complete electron configuration for the following: Ti 2+_____________________________________ Cr_______________________________________

N______________________________________

7. Calculate the standard enthalpy of formation ( ï Ho) for diamond from graphite [i.e. C (graphite) ï C (diamond)] given that:

C (graphite) + O2 ï CO2 (g) ( ï Ho = -393.5 KJ/mole) C (diamond)] + O2 ï CO2 (g) ( ï Ho = -395.4 KJ/mole)

If 1.0g of graphite is converted to diamond, what is the energy change? Is this an endothermic or exothermic reaction?

8. An 160 pound astronaut on his way to Mars is buzzing along at 10,000 miles per hour. (a) Express his weight in grams (one pound = 454 grams) so that you can calculate the astronautâs wavelength (1mile/hour = 44.7 cm/sec)

(b) Suppose the astronaut detects outside his spacecraft a proton (m=1.7 x 10-24 g) from a âsolar windâ moving at exactly the spacecraft velocity. What is the proton wavelength is in AÌ (1 AÌ = 10-8 cm.

9. What is the maximum number of electrons that can occupy each of the following subshells? a) 3d_________________ b) 1s____________________ c) 2p ____________________

10. Identify the element represented by the following electronic configuration.

a) [Ne] 3s2____________________

b) What is the electron configuration for the first excited state of this atom.______________

11. Determine the number of valence electrons for each element.
(a) Br___________ (b) Na _________ (c) Sn __________

12. 175 g of Fe at 15.0oC is mixed with 225 g of H2O at 95.0oC. What is the final temperature of the mixture? The specific heats of iron= 0.448 J/g oC and water = 4.184 J/g oC). (keep in mind the following: heat gained + heat lost = 0 and q=mass x heat capacity x ïT)

13. (5 pts) Calculate values of ÎHrxn for the following reactions: CS2(g) + 3O2(g) ï® CO2(g) + 2SO2(g)

The heat of formation for the following substances is given in kJ/mol:

CS2 CO2 SO2 117.4 -393.51 -296.83

14. (6 pts) Use the electron configuration of Li and Be and determine which element has the greatest second ionization energy. Defend your answer.

15. Mark beside each of the following processes either âexoâ or âendoâ according to whether you think the process will release heat or absorb heat.

a. Ca(g) ï Ca(g)+2 + 2e-
b. I(g)+1e-ï I(g)-1
c. Ca(g)+2 + S(g)-2 ï CaS(s) d. I2(g)ï 2I(g)

( ) ( ) ( ) ( )

16. (6 pts) In each of the following pairs, which of the two species is larger?
a) O-2 or Na+ b) Ti+4 or Ti+2 c) B or C d) N or N-3

17. Write down the Lewis dot structure for the following (a) N_______________ (b) Ne________________

18. THE BORN HABER CYCLE: I may have a problem on the Born Haber cycle. Please check my lecture notes to see how to set up the process and then calculate the lattice energy from the various thermodynamic quantities such as in the NaCl example below;

ï H ï¯ f NaCl = -411KJ

Na(s) ï® Na(g) ï H =108KJ
1â2 Cl2 ï® Cl(g) ï H = 122KJ Ionization Energy of Na ï H = 496 KJ Electron affinity of Cl ï H = -349KJ

Chemistry 1027A/B Lecture Notes - Lecture 1: Lone Pair, Chemical Polarity, Lewis Structure

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