CHEM 121 Lecture Notes - Lecture 17: Bond Order, Antibonding Molecular Orbital, Atomic Orbital

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CHEM 121 Lecture Notes - Lecture 16: Lattice Energy, London Dispersion Force, Intermolecular Force

CHEM 121 Lecture Notes - Lecture 17: Bond Order, Antibonding Molecular Orbital, Atomic Orbital

CHEM 121 Lecture Notes - Lecture 18: Vanillin, Chemophobia

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Lecture 17 - antibonding, bonding, energy levels and bond order. Hydrogen molecule uses the cross-sections of the 90% probability surfaces. Three characteristics of orbital diagram: (chirp, 8. 11: the symmetry of the orbital: each mo is labelled with the appropriate symbol (if the orbital has cylindrical symmetry) or. (if the orbital has a plane of symmetry containing the bond: whether the orbital is bonding or anti-bonding: an asterisk * indicates antibonding orbital (ex. * is the anti bonding orbital while is the bonding orbital: the aos from which the mo originates: the ao labels are (chirp, subscripts (ex. 1s is the bonding mo derived from the 1s orbitals on adjacent atoms) Bond order = (ebonding - eantibonding) / 2: ebonding- the number of electrons in bonding orbitals, eantibonding- the number of electrons in anti-bonding orbitals. Exercises: calculate the h-h bond order in h2 molecule in the ground state.

Related Questions

The molecular orbitals associated with the Ï-bonding MOs insquare cyclobutadiene (C4H4) are, like benzene, form by overlap ofa single p-orbital on each carbon atom that is not involved in thesigma-bonding network of the molecule. These p-orbitals pointperpendicularly with respect to the plane defined by the carbonatoms. There is no central atom, so the only interactions thatmatter are between the p-orbitals among themselves. These MOs haveexactly the same phase relationship as the SALCs you just made inquestion 1. i) Use your results from question 1 to draw the fourÏ-orbitals of C4H4. ii) Use the idea that the energy of a MOincreases with number of new nodes made during bonding (i.e. nodesnot already present in initial AO functions) to sketch a molecularorbital energy level diagram for the Ï-molecular orbitals of C4H4.Remember that, by definition, degenerate orbitals are identicalexcept for trivial rotation in space, and have identical energy.iii) Fill the MOs with the electrons from the atomic p-orbitalsthat you used to form the Ï-MOs of C4H4. Use your diagram todetermine the overall bond order by considering each doublyoccupied bonding MO to contribute 1, each nonbonding orbital 0 andeach antibonding orbital -1. The result would be divided by 4 C-Cbonds to get the average contribution to each C-C bond fromÏ-bonding, which then should be added to a Ï-bonding contributionof 1.0. iv) Repeat step (iii) for the dication C4H4 2+ to determinethe net bond order for this species. Why do you think you got thisvalue? v) Predict which of C4H4 and C4H4 2+ could be observed byESR spectroscopy. vi) Which of C4H4 2+ and C4H4 is more likely tobe susceptible to electrophilic attack.

Which of the following does not have a more stable resonance structure?

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Question 21 pts

In the following molecule, which carbons are electron deficient, meaning they hold a partial positive charge (Î´+) in the hybrid structure. All carbon atoms are identified by a number.

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Question 31 pts

Rank the following resonance structures from most to least stable.

III (most stable) > I > II (least stable)

III (most stable) > II > I (least stable)

I (most stable) > II > III (least stable)

II (most stable) > III > I (least stable)

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Question 41 pts

Which of the following accurately depicts a Lewis acid-base reaction where a carbon is acting as the Lewis acid and an oxygen is acting as the Lewis base.

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Question 51 pts

Which of the following statements about Lewis acids and bases is true?

A Lewis base always accepts an electron pair from a Lewis acid.

The interaction between a Lewis acid and a Lewis base creates a covalent bond.

Lewis acids are also commonly called nucleophiles.

A Lewis base always accepts a proton (H+) from a Lewis acid.

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Question 61 pts

A molecular orbital energy diagram was created that contains two bonding orbitals and two antibonding orbitals. How many atomic orbitals were mixed to create all these orbitals?

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Question 71 pts

Which of the following statements about the molecular orbital diagram for H2â is false?

Two atomic orbitals combine to produce two molecular orbitals.

There is one filled bonding orbital.

There is one empty antibonding orbital.

There is a non-zero bond order.

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Question 81 pts

If a p atomic orbital and an s atomic orbital were to interact and combine to create new molecular orbitals, how many antibonding molecular orbitals would be created?

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Question 91 pts

Which of the following contains an aldehyde, an ether and an alcohol? Choose all that apply.

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Question 101 pts

Which of the following contains a carboxylic acid and an ether? Choose all that apply.

7.
Calculate the percentage, by mass, of fluorine in sulfurhexafluoride (SF6), a potent greenhouse gas.
A) 78.0%
B) 59.2%
C) 22.0%
D) 82.1%
E) 85.7%

8.
Octane (C8H18) is one of the principal components of gasoline. Howmany moles of CO2 are produced during the combustion of 3.0 mol ofoctane?
Unbalanced equation: C8H18 + O2 --> CO2 + H2O
A) 3.0
B) 26
C) 24
D) 8.0
E) 4

9.
How many atoms are present in 0.375 mol of palladium (Pd)atoms?
A) 6.23 x 1021
B) 2.26 x 1023
C) 6.02 x 1023
D) 1.61 x 1024
E) 2.12 x 1021

10.
How many molecules are present in 1.0 kg of hydrogen (H2)gas?
A) 6.0 x 1023
B) 3.0 x 1026
C) 6.0 x 1026
D) 3.0 x 1023
E) 1.7 x 1025

11.
What evidence indicates that the rising atmospheric CO2 levels arecaused by the combustion of fossil fuels?
A) Both the average global temperature and the atmospheric CO2level have risen.
B) The 14C/12C ratio in atmospheric CO2 is unusually low.
C) Increased precipitation in most of the NorthernHemisphere.
D) The 18O/16O ratio in atmospheric CO2 is the same as inatmospheric oxygen.
E) The level of atmospheric moisture has increased.

12.
Heat is a form of
A) Energy
B) Pressure
C) Work
D) Volume
E) Temperature

13.
Oxygenated gasolines
A) Are gasolines that have oxygen gas bubbled through them
B) Contain nitrogen containing compounds
C) Are formulated to contain water
D) Have higher activation energies for combustion than regulargasolines.
E) May contain MTBE or ethanol

14.
A chemical reaction accompanied by a release of energy is calleda/an ______ reaction.
A) exothermic
B) fast
C) activated
D) catalyzed
E) endothermic

15.
The diagram below shows a simplified version of a fractionatingcolumn used in the petroleum industry.

The compounds with the lowest boiling points are condensed atposition

A) C.
B) D.
C) B.
D) A.

16.
Where is most of the carbon on earth stored?
A) in the form of fossil fuels
B) in the deep ocean
C) in the atmosphere
D) in surface water
E) in the forests and soil

17.
Find the molar mass of ethanol, C2H6O.
A) 22.1 g/mol
B) 26.0 g/mol
C) 46.07 g/mol
D) 45.06 g/mol
E) 29.02 g/mol

18.
Determine the shape or geometry of PH3. (Hint: Use the PeriodicTable to arrive at the electron configuration forphosphorous.)
A) trigonal planar
B) linear
C) trigonal pyramidal
D) bent
E) tetrahedral

19.
The energy stored in the chemical bonds of fossil fuels is a formof ______ energy.
A) nuclear
B) potential
C) mechanical
D) kinetic
E) electrical

20.
The heat of combustion of methane, CH4, is 50.1 kJ/g. How much heatwould be generated if 1.00 mol of methane undergoes completecombustion?
A) 50.1 kJ
B) 804 kJ
C) 601 kJ
D) 0.32 kJ
E) 3.12 kJ

21.
Methane is approximately 23 times more powerful than carbon dioxideas a greenhouse gas. Which are significant sources of methaneemissions?
I. The digestive systems of ruminants (cows, sheep, etc.)
II. Automobile exhaust
III. Rice cultivation
IV. Decaying wetland vegetation
A) I and II only
B) I only
C) All of these
D) II only
E) I, III, and IV only

22.
Which atmospheric component does not contribute to globalwarming?
A) CH4
B) CO2
C) CFC
D) N2
E) H2O

23.
What is the effect of infrared energy on matter?
A) It breaks chemical bonds.
B) It excites bonding electrons.
C) It increases molecular rotation.
D) It increases the vibration of chemical bonds.
E) It excites non-bonding electrons.

24.
According to current estimates, the fuel in greatest abundance onearth is
A) natural gas.
B) hydrogen
C) uranium.
D) coal.
E) petroleum.

25.
A gasoline's octane rating is a measure of the
A) purity of the gasoline.
B) energy content of the gasoline.
C) percent of gasoline that contains octane
D) pollutants produced by burning the gasoline in a vehicle'sengine.
E) gasoline's resistance to causing knocking in a vehicle'sengine.

26.
Advertising claims sometimes state that adding something mechanicalto a car's engine will allow it to recover 100% of the energy thatcomes from burning gasoline. You should be skeptical of such claimsbecause they are not consistent with the
A) first law of thermodynamics.
B) energy difference between reactants and products
C) second law of thermodynamics.
D) law of conservation of matter.
E) activation energy requirements of all chemical reactions.

27.
In order to make useful predictions, which factors must beaccounted for by climatic models?
I. Cooling effect of atmospheric aerosols
II. Smoke, haze, and cloud cover
III. Change in land use
IV. Combustion of fossil fuels
A) III and IV only
B) II, III, and IV
C) II and III only
D) I, II, III, and IV
E) IV only

28.
Use the equation to help you calculate the heat of combustion ofethylene, C2H4. The bond energies are: C H 416 kJ/mol; C C 598kJ/mol; O O 498 kJ/mol; C O 803 kJ/mol; H O 467 kJ/mol.

The heat of combustion of ethylene is

A) 1216 kJ/mol.
B) 220 kJ/mol.
C) 1324 kJ/mol.
D) 754 kJ/mol.
E) 242 kJ/mol.

29.
Scientists believe they know the average global temperature overthe last 160,000 years. Which property of the ice core samples fromAntarctica provides this information?
A) the 1H/2H ratio
B) the density of the ice
C) the thickness
D) the temperature
E) the carbon dioxide concentration

30.
(Both the Clinton) and the George W. Bush administrations have beenunwilling to sign the Kyoto Protocol. What has been a stated reasonfor their objection to the treaty?
A) Enforcement of the treaty will be impossible.
B) Lack of conclusive evidence that increased atmospheric CO2 leadsto global warming.
C) The target emission levels are not sufficiently low to affectthe greenhouse effect.
D) The treaty does not include a provision for trading emissionallowances.
E) Developing countries are not required to control greenhouse gasemissions.

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CHEM 121 Lecture Notes - Lecture 17: Bond Order, Antibonding Molecular Orbital, Atomic Orbital

CHEM 121 Lecture Notes - Lecture 16: Lattice Energy, London Dispersion Force, Intermolecular Force

CHEM 121 Lecture Notes - Lecture 17: Bond Order, Antibonding Molecular Orbital, Atomic Orbital

CHEM 121 Lecture Notes - Lecture 18: Vanillin, Chemophobia

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