Presentatiion of chemical reactions, including ideal gas law &solutions

1. 7. Chemical reactions
1. Introduction to Chemistry
2. Chemical reactions
3. Gas laws
4. Concept of mole
5. Solutions
6. Energy of chemical reactions
7. Reaction rates

2. 1. Chemistry
Science which studies
composition, properties
and transformations of
mixtures and chemical
substances

3. 1. Mixtures & substances
Phase: portion of uniform
matter which is limited a clear
boudndary
Heterogeneous mixture:
portion of matter which
consists of different phases
Homogeneous mixture
portion of matter which
consists of just one phase
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4. 1. Mixtures & substances
• Substance homogeneous
phase which has a fixed
composition
• Formula air vs. NO2
1. Elements, which consist
of the same type of
atoms
2. Compounds, which are
combinations of
different elements

5. 2. Chemical reactions
Chemical reaction
process in which some substances
(reactants) are combined and
produce others which are called
products
Stoichiometry: any ratio or
proportion between elements in a
compound or substances which take
part in a chemical reaction

6. 2. Conservation of mass law
(Lomonosov & Lavoisier, 1783)
“the sum of the masses of reactants is equal to
the sum of the masses of the products of the
reaction”
reaction as rearrangement of chemical bonds
Number of atoms remains constant
An amount of energy is absorbed or released

7. 2. Chemical equations
Representation of a chemical reaction
expresión which shows:
Reactants and products
proportion in which they are combined
(stoichiometry)

8.
3. Ideal gas law
Boyle´s law (1656)
When temperature remains
constant, pressure of a gas is
inversely proportional to its
volume
p.V = constant

9. 3. Ideal gas law
Charles law (1787)
When pressure remains the
same, the volumen occupied by
a gas is proportional to its
temperature
V = Vo + k.t
Kelvin: 0 K = - 273,159º C.
V = cte.T

10. 3. Ideal gas law
Gay-Lussac 2nd
law (1802)
When volume remains the same, the
pressure of a gas is proportional to its
temperature
p = k.T

11. 3. Ideal gas law
Gay-Lussac (1809)
“Volumes of gases combined in a
chemical reaction are related
according to an integer ratio”

12. 3. Ideal gas law
Avogadro hypothesis (1811)
“Equal volumes of different gases, at
the same conditions of pressure and
temperature have the same number
of molecules.
Cannizaro (1870):
First atomic masses table

13. 3. Ideal gas law
equiation which relates state
variables (temperature, volume,
presure)
p.V = n.R.T
E. Clapeyron (1834)
Ideal gas constant:
R = 0,0819 at.l.mol-1
.K-1
= 8,31 J.mol-1
.K-1

14. 4. Concept of mole
• Amount of substance is a
physical quantity which
measures the number of
molecules, atoms or ions in
a portion of matter
• SI unit: moles, equivalent
to 6,022.1023
partícles.
Avogadro number.
• The mass of one mole of
any substance is the atomic
or molecular mass
expressed in grams

15. 5. Solutions
Homogeneous mixture in
liquid phase
Solvent
Solute
Colloids vs. solutions

16. 5. Concentration of solutions
• Mass percentage: ratio of the mass of
a component to the total mass of the
solution
• Molar fraction : ratio of the
amount of a substance to the total
amount of the solution
xi = ni / nt ∑ xi = 1
• Molar concentration (molarity) :
amount of substance per unit of
volume
M = n / V

17. 6. Energy of chemical reactions
Endothermic reactions:
absorb energy (heat) from
their surroundings
 Decrease of temperature
 Exothermic reactions:
release energy (heat) to their
surroundings
 Increase of temperature

18. 7. Reaction rates

19. 7. Factors affecting reaction rates
 Activation energy
 Temperature
 Concentration of the reactants
 Surface area
 Catalysts