General chemistry 2nd year engineering course

8/10/2019 General chemistry 2nd year engineering course

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Course 2

General Chemistry Course


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The Periodic Table

Organization of the periodic table

The periodicity

Periods. To construct the table, we place each sequence in a separate row,

which we call a period .The rows are aligned in such a way that the elements in each vertical columnpossess certain similarities.

Groups. Each column of the periodic table is known as a group . The elementsbelonging to a given group bear a strong similarity in their chemicalbehaviors.


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Periods in the Periodic Table


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Groups in the Periodic Table

Elements in groups react in similar ways!


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Regions of the Periodic Table


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Group 1A: Alkali Metals

Cutting sodium metal

Reaction of

potassium + H 2O


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Magnesium

Magnesiumoxide

Group 2A: Alkaline Earth Metals

MgO


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Group 7A: The Halogens (salt makers) F, Cl, Br, I, At


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Group 8A: The Noble (Inert) Gases He, Ne, Ar, Kr, Xe, Rn

Lighter than air balloons Neon signs Very Unreactive because they

have full electron levels

XeOF 4


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Transition Elements

Lanthanides and actinidesIron in air givesiron(III) oxide

Fe 2O 3


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Mixture

Heterogen Homogen

CompoundsElements

MoleculesAtoms

Nucleus Electrons

Macroscopicscale

Microscopic

scale

Physical process

Physical process

Chemical process

Chemical process


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W. Tho ms on develops the plum pudding model: a cloud of positive charges; randomly distributed electrons.

E. Ruth erford develops an experimental model where the particle (the charge is +2and the relative atomic weight is 4) depart from the source and pass through a thin goldfoil.He registers the deviation of the particles:

most of the particles are not deviated (there is plenty of empty space in the

atom); some of the particles are slightly deviated (there are negatively charged particles, with much lower mass then the particles, in the atom theelectrons); few particles are turned (there is a concentrated, positive atomic charge withthe mass comparable to the particles).

The structure of the atom (Atomic structure)


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all the positive charge and quite the entire mass of atom is concentrated in anucleus; the electrons are surrounding the nucleus.

The chemical reactions do not affect the nucleus. The sum of the protons in thenucleus is called atomic number (Z) .

+11p proton 01n neutron

The sum of the proton and neutron is called mass number (A) . Two species havingthe same Z and different A are isotopes .

E.g. 11H (proton); 21D (deuterium); 31T (tritium)

Conclusion: Nuclear model


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There are not two species with all the quantum numbers equal (Paulis Exclusion

Principle).

n = principal quantum number describes the energetic level of orbital (how far is theorbital from the nucleus); n = 1, 2,3 .

l = azimuth quantum number describes the shape of the orbital; for n fixed,

l = 1, 2,3, (n -1)

m = magnetic quantum number describe the orientation of the orbital; for n,l fixed,m = -l, -(l-1), -(l- 2), , 0, , (l -2), (l-1), l

s = spin number describe the electron movement around its own axis,

s= +1/2 and 1/2

Some rules for filling the orbital up


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In one orbital there are maximum two electrons.

1s

2s

2p 3s

3p 4s

3d 4p 5s

4d 5p 6s

4f 5d 6p 7s

5f 6d 7p 8s

E.g.

11 Na31 Ga

Consequence


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Chemical elements

Every elements is characterized by:

- name;- chemical symbol.

Atomic number = proton number from thenucleus (its also the electron numbers)

Chemical symbol

Atomic mass

Information from the periodictables of the elements


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Atomic mass

MA = p i m i pi = isotopic abundancemi = isotopic mass

Units: 12 daltons = atomic mass of 12C

1 daltons (Da) = 1.660510 -24 g

E.g. Chlorine35Cl: 75,5% 37Cl: 24,5%

MA = 350,755 + 370,245 = 35,5

MA exacte = 35,453


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Molecular Mass (MM)

MM = n iMAi

n i = no of atoms iMA

i = atomic mass of atoms i

E.g.

Water H 2OMM = 21,008 + 115,999 = 18,015 daltons

Glucose C 6H12 O6

MM = 612,011 + 12 1,008 + 615,999 = 180,156 daltons


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Ions

An ion is as atom or molecule which has lost or gained one or moreelectrons, making it negatively or positively charged.

Formation of positive charged ions ( cation )

Atome Cations + Electrons

Cu Cu+1 + 1e -Cu Cu+2 + 2e -

Formation of negative charged ions ( anions)

Atoms + Electrons Anions

Cl + 1e - Cl-1

S + 2e- S

-2


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Remember from the first chemistry course

Mole is a quantity of substance containing NA particles

Particles = atoms, molecules or ionsNA = 6.02210 23 atoms/mol

Molar Mass (MM)Mass of one mol from a substance, expressed in grams

The molar mass is equal with the molecular mass (or atomic), expressedin grams.

E.g. water H2O

Molecular mass = 18.015 Da ; Molar mass = 18.015 mol/g


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Exercise

Water1. How many moles are in 1kg of water?

1000 g / 18.015 g/mol = 55,5 mol

2. How many molecules are in 1kg of water?

55,5(6,02210 23 ) = 3,3410 25 molecules

Iron MA = 55,8471mole = 55,847g, contain 6,02210 23 atomes

3. How many atoms are in 1g?

1g / 55,847 g/mol = 0.0179 mol0,0179(6,02210 23 ) = 1,07810 22 atoms


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The Chemistry Laws


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Ca(OH) 2 + 2HNO 3 Ca(NO 3)2 + 2H 2OCalcium hydroxide + Nitric acid Calcium nitrate + Water

Consequence: the coefficients


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The low of perfect gas

An perfect gas is a gas where the molecules dont sufferany interactions.

PV = nRT

P pressure (Pascal Pa, 1 Pa = 1Nm -2 = 1kgm -1 s -2;1 atm = 1,01410 5 Pa

V volume (m3)

n moles number

T temperature (K)

R perfect gas constant (8,31 Jmol-1

K-1

= 8,31 kgm2

s-2

mol-1

K-1


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Exercise

1) What is the volume occupied by 1 mol of perfect gas at 0 C and1 atm?

n = 1T = 273,15 KP = 1 atm = 1,01410 5 Pa

V = nRT / P = (18,31273,15) / 1,01410 5 = 2,27010 3 / 1,014105 =2,2410-2 m 3

1m3 = 1000litres, V = 22,4 liters1 mol occupied 22,4 liters at 0C and 1 atm


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Exercise

2) What is the volume occupied by 1 mol of perfect gas at 25 Cand 1 atm?

n = 1T = 298,15 KP = 1 atm = 1,014105 Pa

V = nRT / P = (18,31298,15) / 1,014105 = 2,47810 3 / 1,01410 5 = 2,4410-2 m 3

1m3 = 1000litres, V = 24,4 liters1 mol occupied 24,4 liters at 25C and 1 atm


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E inorganic acid = M acid / number of hydrogen atomse.g.EH2SO 4/SO 42- = M/2 = 98/2

Eorganic acid = M acid / number oh carboxyl groups

Ebases = Mbases / number of hydroxide groupse.g.ENaOH = M/1 = 40/1

E salt and metallic oxide = M / number of metal atoms x valencee.g.ECaO = M/2*1 = 56/2

E electrochemical reaction = A element / number of exchanged electronse.g. 2Al + 3 Cl 2 = 2AlCl 3 E

Al = A

Al/3 = 27/3

Calculation of chemical Equivalents

The Law of chem ical equ ivalents the ratio between the mass and the chemicalequivalent is a constant for each participant in a chemical reaction.

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General chemistry 2nd year engineering course