Tutorial #2 – Chapters 5-8

Dr. Truong Thanh Tu

Department of Physical Chemistry

Faculty of Chemistry

19 Le Thanh Tong, Hoan Kiem, Hanoi

tuthanhtruong@gmail.com

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Chapter 5 – Some types of chemical reactions

Periodic table of the elements Reactions in aqueous solutions: formula, total ionic, and

net ionic equations Oxidation numbers Naming inorganic compounds Classification of chemical reactions:

• Oxidation-reduction reactions• Combination reactions• Decomposition reactions• Displacement reactions• Metathesis reactions

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Exercise

Assign oxidation numbers to the element specified in each group of ions

(a) P in PCl5, P4O6, P4O10, HPO3, H3PO3, POCl3, H4P2O7, Mg3(PO4)2

(b) Mn in MnO, MnO2, Mn(OH)2, K2MnO4, KMnO4, Mn2O7.

(c) O in OF2, Na2O, Na2O2, KO2

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Exercise

Write each of the following formula unit equations as net ionic equation if the two differ? For the redox reactions, identify the oxidizing agent, the reducing agent, the species oxidized and the species reduced

(a) AgNO3(aq) + Cu(s) Cu(NO3)2(aq) + Ag(s)

(b) KClO3(s) KCl(s) + KClO4

(c) AgNO3(aq) + K3PO4(aq) Ag3PO4(s) + KNO3(aq)

heat

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Exercise

Balancing and Classifying reactions

(a) Zn(s) + AgNO3(aq) Zn(NO3)2(aq) + Ag(s)

(b) Ca(OH)2(s) CaO(s) + H2O(g)

(c) HI(g) H2(g) + I2(g)

(d) Cu(NO3)2(aq) + Na2S(aq) CuS(s) + NaNO3(aq)

(e) SO2(g) + H2O(l) H2SO3(aq)

(f) H2SO3(aq) + KOH(aq) K2SO3(aq) + H2O(l)

heat

heat

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Naming compounds

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Precipitation reactions

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Acid-Base reactions

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Oxidation-reduction reactions

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LEO SAYS GER

Lose Electrons = Oxidation

Sodium is oxidized

Gain Electrons = Reduction

Chlorine is reduced

eNaNa10

10 CleCl

Reducing agent

Oxidizing agent

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Chapter 6 – Structure of atoms

Atom = Nucleus (protons + neutrons) + Electrons

Element symbolMass number, A (p+ + no)

Atomic number, Z(number of p+)

XAZ

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Chapter 6

Isotopes

Electron orbital = wave function (characterized by quantum numbers (n, l, m, ms) energy level and 3-D shape of the region in space occupied by a given electron

Quantum numbers:• Principal (n) energy levels• Angular-momentum (l): n values of l, from 0…n-1 3-D shape

• Magnetic (ml): 2l+1 values of ml, from –l…+l spatial orientation

• Spin (ms): +1/2 or -1/2 interaction to a magnetic field

C14

6C12

6

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EnergyLevel

(n)

Sublevels inmain energy

level (n sublevels)

Number oforbitals per

sublevel

Number ofElectrons

per sublevel

Number ofelectrons

permain energylevel (2n2)

1 s 1 2 2

2 sp

13

26

8

3 spd

135

26

10

18

4 spdf

1357

26

1014

32

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Electron configurations of multielectron atoms

Aufbau Principle (“building up”): A guide for determining the filling order of orbitals.

1s

2s 2p

3s 3p 3d

4s 4p 4d 4f

5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f

1s2

2 electrons

2s2

4

2p6 3s2

12

3p6 4s2

20

3d10 4p6

5s2

38

4d10 5p6 6s2

56

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Orbital filling table

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Exercise 1

What is the maximum number of electrons in an atom that have the following quantum numbers? (a) n=2

(b) n=3 and l=1; (c) n=3, l=0 and ml=0; (d) n=3, l=1, ml =-1, and ms=-1/2

What are the values of n and l for the following subshells? (a) 1s; (b) 3s; (c) 5p; (d) 3d; (e) 4f

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Exercise 2

Write the subshell notation that correspond to (a) n=3, l=0; (b) n=3, l=1; (c) n=6, l=1; (d) n=3, l=2

How many individual orbitals are there in the third shell? Write out n, l and ml quantum numbers for each one, and label each set by the s, p, d, f designation

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Exercise 4

Determine the number of electrons in the outer occupied shell of each of the following elements, and indicate the principal quantum of that shell (a) Na; (b) S; (c) Sr; (e) Ba; (f) Br

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Exercise

State Pauli Exclusion principle. Would any of the following electron configuration violate this rule: (a) 1s3; (b) 1s22s22px

2 Explain?

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Chapter 7 – Chemical bonding

Ionic bonds: electron(s) is transferred from one atom to another electrostatic attraction (a cation and an anion)

Covalent bonds: two atoms share several electrons Polar and non-polar covalent bonds Octet rule Lewis structures (electron-dot) S = N – A

• S = # shared electrons• N = # valence shell electrons needed

(N = 8 x #atom + 2 x #H)• A = # available electrons in valence shells

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Exercises

1

2

3

4

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Lewis dot symbols

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Ionic bond

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Ionic bond

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Ionic bond

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Lewis structure

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Exceptions to the octet rule

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Chapter 8 – Molecular structure and covalent bonding theories

VSEPR (Valence Shell Electron Pair Repulsion) theory Electrons in bonds and lone pairs can be thought as

“charge clouds” (regions of high electron density) that repel one another and stay as far apart as possible

Count the number of “charge clouds” and determine the molecular shapes

Predict the molecular polarity based on the molecular shape and individual bond polarities

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Chapter 7/34

Molecular Shapes: the VSEPR Model

Two Charge Clouds

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Chapter 7/35

Molecular Shapes: the VSEPR Model

Three Charge Clouds

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Chapter 7/36

Molecular Shapes: the VSEPR Model

Four Charge Clouds

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Chapter 7/37

Molecular Shapes: the VSEPR Model

Four Charge Clouds

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Chapter 7/38

Molecular Shapes: the VSEPR Model

Five Charge Clouds

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Chapter 7/39

Molecular Shapes: the VSEPR Model

Five Charge Clouds

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Chapter 7/40

Molecular Shapes: the VSEPR Model

Six Charge Clouds

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Chapter 7/41

Molecular Shapes: the VSEPR Model

Six Charge Clouds

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Valence bond (VB) theory

Covalent bonds are formed by overlap of atomic orbitals, each of which contains one electron of opposite spin.

Each of the bonded atoms maintains its own atomic orbitals, but the electron pair in the overlapping orbitals is shared by both atoms.

The greater the amount of overlap, the stronger the bond.

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Sigma bonds

Sigma () bonds exist in the region directly between two bonded atoms.

p orbital p orbital

Sigma bondingmolecular orbital

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Pi bonds

Pi () bonds exist in the region above and below a line drawn between two bonded atoms.

Pi bondingmolecular orbital

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Hybridization of orbitals

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Hybridization of orbitals

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Exercise

Write the Lewis formula for each of the following. Indicate which bonds are polar. Indicate which molecules are polar. (a) CS2; (b) AlF3; (c) H2S; (d) SnF2.

Write Lewis formulas and three dimensional structures for the following (a) BrF3; (b) BrF; (c) BrF5.

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Exercise

What is the hybridization of the central atom in each of the following? (a) NCl3; (b) molecular AlCl3; (c) CF4; (d) SF6; (e) IO4

-

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