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CH13
CHEMISTRY E182019
SUMMARY
and test
This course is approximately at this level
Rudolf Žitný, Ústav procesní a
zpracovatelské techniky ČVUT FS 2010
CH13
SUMMARY and test
Written test consists in
8 questions and one example.
Each question represents 8 points, numerical example 16 points.
Taken together, maximum from the written test is 80 points.
Oral part (discussion of laboratory protocols, and written test) is 20 points.
Rating
A
B
C
D
E
F
90+
80+
70+
60+
50+
..49
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1. Units, constants…
mass
length
temperature
internal energy
m
L
T
U
kg
m
K,oC
J
1 lb=0.45 kg
1 ft=0.3 m
oF=1.8 oC+32, K=C+273.15
1 BTU=1 kJ
mole = 6.02 x 1023 (Avogadro's number)
R = 8.314 kJ/(kmol.K) (Universal gas constant)
MH=1 g/mole, MC=12 g/mole, MN=14 g/mole, MO=16 g/mole
Atmospheric pressure p=1.03·105 Pa
Reference temperature T=298K
Water: Density =1000 kg/m3, cp=4.2 kJ/(kg.K), hLG=2200 kJ/kg, Tc=3740C
Air: Density =1.2 kg/m3, cp=1 kJ/(kg.K),
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1. Concentrations…
Mass concentration
Molar concentration
Molality
Mass fraction
Molar fraction
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1. Units, concentrations…
Example: Calculate mass fraction of oxygen in air assuming volumetric
composition of air 21:79 (MO=16, MN=14).
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2. periodic table,pH, polar/covalent bonds,
the column 1 contains alkali metals, which have one
more electron than the corresponding noble gases
Non-metals Missing electrons
Metals Superfluous electrons
Covalent bond CH4 (shared pairs)
H has 1 electron in valence, C has 4 electrons in valence
hydrogen needs 1 more electron to
complete the valence (s-sublevel)
carbon has only 4 electrons in
valence shell and needs 4 more.
4 pairs of shared electrons complete valences of H, C
Ionic bond NaCl (electrostatic attraction ions)
Na-1 electron in valence, Cl-1 missing electron in valence
sodium lends 1 electron
chlorine borrows this
electron (will have the same
valence shell as stable Ar)
Na+ cation
Cl- anion (negative charge)
the column 18
contains noble
gases which are
inert .
.
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2. pH, polar/covalent bonds, periodic table
Number of free protons H+ in 1 l of water [H+] is related to pH value
pH = - log [H+]
pH < 7
pH >7
acids (concentration of free protons > 10 mol/l)
bases (concentration of free protons < 10 mol/l)
- log
-7
-7
+
[H ][OH ]=14
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2. pH, polar/covalent bonds
How to derive the Lewis formula, given a chemical formula (and charge of ion).
1. Draw a possible structure(s)
2. Calculate total number of valence electrons (– charge of ion in case of ions)
3. Try to distribute these electrons so that all elements fill their valence shell
(octet rule).
Carbon dioxide CO2
(4+2x6)=16 electrons (8 pairs)
.
Sulfate (SO4)2-
(6+4x6) + 2=32 electrons (16 pairs)
2-
O
O=C=O
O
S
O
O-C-O
because there is 10
pairs
O
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2. pH, polar/covalent bonds
Example: Hydrochlorid acid has pH=2. Calculate mass of HCl in 1 l of electrolyte.
Solution: HCl + H2O → H+ + Cl- + H+ + OHDecomposed
HCl
Decomposed
H2O
14 =-log[H+]-log[OH-]=2- log[OH-]
Universal
constant
Total amount of
H+
→
[OH-]=10-12
negligibl
e
Amount of free protons decomposed from HCl is 10-2-10-12 /l
MHCl=36.5 g/mol, for molar concentration 10-2 mass of HCl is 0.365 g
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3. stoichiometry
Stoichiometric coefficients are
negative for reactants and
positive for products
Stoichiometric coefficients are calculated by balancing all elements (each
element represents one homogeneous algebraic equation for i)
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3. stoichiometry
Example: Calculate kg of water that is produced by burning 2 kg of methane.
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4. Enthalpy, entropy, Gibbs
energy
First law of thermopdynamics
δq = du + δw
Internal energy
du = cv dT
Enthalpy
dh = cp dT
h=u+pv
Entropy
ds = (du+pdv)/T=dq/T
Gibbs energy
g=h-Ts
s 
hLG
T
s  cv ln
T2 R v2
 ln
T1 M v1
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4. Enthalpy, entropy, Gibbs
energy
Hess law The enthalpy change of the reaction is a function of state and is
independent of any intermediate reaction.
Standard enthalpy of formation
~0
( h f ,compound ) 298
Enthalpy change of a chemical reaction
( Hr0 )298
~0
~0
  P ( h f , P )298  R ( h f , R )298
P
R
Negative-exothermic,
Positive-endothermic reaction
Gibbs energy change of a chemical reaction
(Gr0 )298  P (g 0f , P )298 R (g 0f , R )298
P
Negative-feasible reaction
R
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4. Enthalpy, entropy, Gibbs
energy
Example: Write definition of specific entropy. Calculate specific entropy
change corresponding to temperature increase of water from 20 to 1000C
assuming constant specific heat capacity of H2O (l) – you should know this
value.
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5. State and phase equations
Antoine
p
ln p  A 
L-liquid
B
C T
S-solid
a VdW
( p  ~ 2 )(v~  b)  RT
v
G-gas
pv 
T
Clausius Clapeyron
dp
h

dT T v
R
T
M
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5. State and phase equations
Multiphase and multicomponent equilibrium
Raoult´s law
pA  pA " xA
Henry’s law
pA  HxA
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5. State and phase equations
Example
What is the correct formulation of Raoult's law?
a) pa/pa"=ya
b) pa/p =ya
c) pa/p =xa
d) pa/pa"=xa
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6. Electrochemistry, Reactions
Oxidation ANODE
Reduction CATHODE
2
Zn  Zn  2e
Cu
2
 2e  Cu
Anode of galvanic
cell is dissolved
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6. Electrochemistry, Reactions
REACTION PROGRESS 
Or how to calculate concentrations
of all participating species knowing
only one scalar variable
k
 A A   B B 
 C C   D D
 
nA  nA0

nB  nB 0

nC  nC 0

nD  nD 0
A
B
C
D
 cA  cA0 cB  cB 0 cC  cC 0 cD  cD 0
[ ]  



V
A
B
C
D
dci  i d [ ]
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6. Electrochemistry, Reactions
REACTION RATE
AB+C
A+BC
d [ ] 1 dci
r

dt
i dt
dcA
  Ae
dt
dcA
  Ae
dt
Ea

RT

Ea
RT
Activation
energy
cA
cAcB
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6. Electrochemistry, Reactions
Reversible REACTION
 A A  B B
C C  D D
Equilibrium constant (in terms partial pressures and concentrations)
pC pD cC cD
Kp 

p A p B c A cB
Equilibrium constant (as a function
Kp  e
0
Greaction

RT
of temperature and Gibbs energy)
 E2
A1  E1RT
 e
A2
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6. Reactions
Example: If you combine potassium and chlorine in a galvanic cell,
what will be anode? Estimate resulting voltage of this cell.
Standard reduction potentials
[Malinovský 1987]
Half-reaction
Eo/V

-2.925
K e  K
2
-0.763
Zn  2e  Zn
0
2 H   2e  H2
0.337
Cu 2  2e  Cu

0.799
Ag  e  Ag
1.23
Cl2  2e  2Cl 
2
1.5
Au  2e  Au
Table of reduction potentials
will be given as a part of
problem setting
Example: Reaction rate increased 2 times, when reaction temperature
was increased from 10000C to 12000C. Calculate activation energy of
the reaction.
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7. Organic chemistry
ALKANES linear chains containing single bonds
Derived alkyl
groups -R
ALKENES linear chains containing at least one double bond
ALKYNES linear chains containing at least one triple bond
AROMATIC ring structure with alternating single and double bonds
Derived
aryl groups
-R
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7. Organic chemistry
functional group derived from alkanes
-CH3 (methyl), -C2H5 (ethyl), -C3H7 (propyl), … (alkyl groups)
-OH (hydroxyl group /alcohols/),
-COOH (carboxyl group /acids/),
-NH2 (amines),
-CONH2 (amides).
Connecting functional groups
-O- (ethers),
R-CO-R (ketones, carbonyl group), R-CO-H (aldehydes)
-COO- (esters /fats/).
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7. Organic chemistry
Example: Classify and name the following compound
O
CH3CH2-C-H
Solution: ethylaldehyde
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8. Polymers, Biochemistry
Can be anything, for example
amyl or aryl groups, halogens
R
H
C
C
H
H
Polyolefines
N=..
.
Polyamides
Amide group
H
H
H
H
H
H
N
C
C
C
C
C
C
N
H
H
H
H
H
H
H
H
O
H
H
H
H
O
C
C
C
C
C
C
H
H
H
H
Polyhexamethylene adipamide (nylon 6/6)
N
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8. Polymers, Biochemistry
Biomolecules - polymers (except lipids)
Nucleic acids
Lipids
Carbohydrates
e.g.Fats
e.g.Starch
Cellulose
DNA
Proteins
RNA
Amino acids
(CH2O)6n
H
N
C6H12O6 fructose,
glucose
H
R
O
C
C
H
O
H
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8. Polymers, Biochemistry
Example: What is polyethylene (write formula)?
Example: Classify starch and cellulose (what is it: protein,
carbohydrate, lipid, or acid?). Describe differences.
Final example
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Reaction enthalpy, spontaneity of
chemical reaction (temperature
range), equilibrium constant
Given data from the following table, calculate maximum of what can be said
about the chemical reaction: fermentation of ethylalcohol
(~
s 0 ) 298
~
( hf0 ) 298
( g~f0 ) 298
kJ.mol-1.K-1
H2(g)
0.13057
N2(g)
0.19150
O2(g)
0.20503
C(s)
0.00574
CO(g)
0.19756
CO2(g)
0.21360
CH4 (g)
0.18615
C2H5OH(l) 0.16100
C6H6(l)
0.17280
kJ.mol-1
0
0
0
0
-110.5
-393.5
-74.8
-277.7
49.0
kJ.mol-1
0
0
0
0
-137.1
-394.4
-50.8
-144.9
129.7
Substance
Substance
(~
s 0 ) 298
~
( hf0 ) 298
( g~f0 ) 298
kJ.mol-1.K-1 kJ.mol-1
kJ.mol-1
CaO(s) 0.04000
-635.5
-604.2
CaSO4(s) 0.10700
-1432.7
-1320.3
H2O(g) 0.18871
-241.8
-228.6
NH3(g) 0.19230
-46.1
-16.5
NO(g)
0.21065
90.2
86.6
NO2(g) 0.23990
82.1
104.2
SO2(g) 0.24810
-296.8
-300.2
SO3(g)
0.2566
-395.7
-371.1
S8(s)
0.2540
0
0