aula #03 · aula #03. dalton’s atomic theory 2. 16 x + 8 y 8 x 2 y proportion /relation between...
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Aula #03
Dalton’s Atomic Theory
2
8 X2Y16 X 8 Y+Proportion /relation between matter
atomic radius ~ 100 pm = 1 x 10-10 m
nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m
Rutherford’s Model of the Atom
What made by Rutherford and his
assistants Geiger and Marsden is perhaps one of the most important experiments of nuclear physics.
1. atoms positive charge is concentrated in the nucleus
2. proton (p) has opposite (+) charge of electron (-)
3. mass of p is 1840 x mass of e- (1.67 x 10-24 g)
particle velocity ~ 1.4 x 107 m/s(~5% speed of light)
(1908 Nobel Prize in Chemistry)
Alfa -particlehelium-4 nucleus
- Neutron, n - Protons, He2+
- Electrons, e
Atomic number, Mass number and Isotopes
Atomic number (Z) = number of protons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Isotopes are atoms of the same element (X) with
different numbers of neutrons in their nuclei
XA
Z
H1
1H (D)
2
1H (T)
3
1
U235
92U238
92
Mass Number
Atomic NumberElement Symbol
Isotopes are atoms of the same element (X)
with different numbers of neutrons in their nuclei
XA
Z
Mass Number
Atomic NumberElement Symbol
U235
92
92 protons, 92 electrons
143 (235 - 92) neutrons,
Atomic number, Mass number and Isotopes
Mass Relationships in Chemical Reactions
Atomic/Nano/Micro Worldatoms & molecules
Macro WorldGrams; tons
The mole (mol) is the amount of a substance that contains as many elementary entities as there
6.022140857 × 1023
are atoms in exactly 12.00 grams of 12C
Avogadro’s number (NA) 6.022 140 76 × 1023
Mass Relationships in Chemical Reactions
The mole (mol) is the amount of a substance that contains as many elementary entities as 6.022 140 76 × 1023
there are atoms in exactly 12.00 grams of 12C …IUPAC 2018
http://physics.nist.gov/cgi-bin/cuu/Value?na
Lorenzo Romano Amedeo Carlo Avogadro
On this scale
1H = 1.008 amu
16O = 16.00 amu
Atomic mass is the mass of an atom in atomic mass units (amu)
Natural abundance of lithium:
6Li (6.015 amu) 7.42%
7Li (7.016 amu) 92.58%
Average atomic mass of lithium:
7.42 x 6.015 + 92.58 x 7.016
100= 6.941 amu
Li
Average atomic mass (6.941)
= 6.941 amu
Li
Mass Relationships in Chemical Reactions
Atomic/Nano/Micro Worldatoms & molecules
Macro WorldGrams; tons
Avogadro’s number (NA) 6.022140857 × 1023 mol-1
1 mole (mol) Li MW=6.941 g/mol 6.941 gram
1 mole (mol) C MW=12.0107 g/mol 12.0107 gram
Mass Relationships in Chemical Reactions
Carbon 12.0107 gSulfur 32.065 gMercury 200.59 gCopper 63.546 gIron 55.845 g
One Mole of:
Mass Relationships in Chemical Reactions
6x (12.0107) + 12x(1.00794) + 6x(15.9994)
180.1559 gmol-1
Mass Relationships in Chemical Reactions
How many molecules are in 5.0 g of Saccharose ?
342.2965 gmol-1
Formula: C12H22O11
Molar mass: 342.2965 g/mol
5.0 g
Avogadro’s number (NA)
x 6.022140857 × 1023 mol-1
mol
= 12 x 8.8 × 1021 atoms of C
= 8.8 × 1021 molecules of Saccharose
= 22 x 8.8 × 1021 atoms of H
= 11 x 8.8 × 1021 atoms of O
Mass Relationships in Chemical Reactions
5.0 g of Saccharose ?
Formula: C12H22O11
Molar mass: 342.2965 g/mol
Avogadro’s number (NA)
6.022140857 × 1023 mol-1
20 milhões x 20 milhões x 20 milhões
= 8.8 × 1021 molecules of Saccharose
Mass Relationships in Chemical Reactions
Mass Relationships in Chemical Reactions
%C =2 x (12.01 g)
46.07 gx 100% = 52.14%
%H =6 x (1.008 g)
46.07 gx 100% = 13.13%
%O =1 x (16.00 g)
46.07 gx 100% = 34.73%
52.14% + 13.13% + 34.73% = 100.0%
C2H6O
Ethanol
Percent composition of an element in a compound =
n x molar mass of element
molar mass of compoundx 100%
Mass Relationships in Chemical Reactions
nK = 24.75 g K x = 0.6330 mol K1 mol K
39.10 g K
nMn = 34.77 g Mn x = 0.6329 mol Mn1 mol Mn
54.94 g Mn
nO = 40.51 g O x = 2.532 mol O1 mol O
16.00 g O
Empirical formula of a compound that has the following percent composition by mass:
K= 24.75% , Mn= 34.77%, O= 40.51%
Base ..100 g
K : ~~ 1.00.6330
0.6329
Mn : 0.6329
0.6329= 1.0
O : ~~ 4.02.532
0.6329
nK = 0.6330, nMn = 0.6329, nO = 2.532
KMnO4
Mass Relationships in Chemical Reactions
Combustion 11.5 g ethanol
Collect 22.0 g CO2 and 13.5 g H2O
g CO2 mol CO2 mol C g C
g H2O mol H2O mol H g H
g of O = g of sample – (g of C + g of H)
6.0 g C = 0.5 mol C
1.5 g H = 1.5 mol H
4.0 g O = 0.25 mol O
C0.5H1.5O0.25
Divide by smallest subscript (0.25)
Empirical formula C2H6O
Ethane reacts with oxygen to form carbon dioxide and water
C2H6 + O2 2 CO2 + 3 H2O
Balancing Chemical Equations
C2H6 + O2 CO2 + H2O
multiply O2 by 72
C2H6 + 7/2O2 2 CO2 + 3 H2O
2C2H6 + 7O2 4CO2 + 6H2O
Balancing, C & H
Mass Relationships in Chemical Reactions
2NO + 2O2 2NO2
NO is the limiting reagent
O2 is the excess reagent
limiting reagent
Mass Relationships in Chemical Reactions
In one process, 124 g of Al are reacted with 601 g of Fe2O3
2Al + Fe2O3 Al2O3 + 2Fe
Calculate the mass of Al2O3 formed.
g Al mol Al mol Fe2O3 needed g Fe2O3 needed
OR
g Fe2O3 mol Fe2O3 mol Al needed g Al needed
Mass Relationships in Chemical Reactions
In one process, 124 g of Al are reacted with 601 g of Fe2O3
2Al + Fe2O3 Al2O3 + 2Fe
Calculate the mass of Al2O3 formed.
g Al mol Al mol Fe2O3 needed g Fe2O3 needed
OR
g Fe2O3 mol Fe2O3 mol Al needed g Al needed
124 g /26.98 gmol-1
= 4.60 mol
601 g /159.688 gmol-1
= 3.76 mol
4.60/2 = 2.30 mol
3.76x2 = 7.52 mol
Mass Relationships in Chemical Reactions
Theoretical Yield is the amount of product that wouldresult if all the limiting reagent reacted.
Actual Yield is the amount of product actually obtainedfrom a reaction.
% Yield = Actual Yield
Theoretical Yield
x 100
Glass transition
Liquid Nitrogen
Liquid nitrogen is
nitrogen in a liquid state at an extremely low temperature.
It is a colorless liquid with a density of 0.807 g/ml at
its boiling point (−195.79 °C (77 K; −320 °F))
Liquid nitrogen
liquid nitrogen can be stored and transported,
for example in vacuum flasks.