Using English to Calculate

STOCIOMETRY

1.                 Basic Law of Chemistry Law

A.    The Law of Conservation of Mass (Lavoisier's Law)

Antoine Laurent Lavoisier (1743-1794) a French chemist has investigated the mass relationship of substances before and after the reaction. Lavoisier weighed the substances before reacting then weighing the reactions. It turns out that the mass of substances before and after react is always the same. However, material changes generally take place in an open system so that when a reaction product leaves the system (such as a candle burning) or when something of a substance from the environment is bound (such as an iron-bonding process that binds oxygen from the air) it is as if the mass of matter before And after the reaction becomes unequal. From Lavoisier's experiments on liquid mercury and oxygen to forming red mercury oxide, Lavoiser draws conclusions known as mass conservation laws:

"The mass of substances before and after the reaction is fixed".

B.    Comparable Law of the Law (Proust Law)

There are various compounds formed by two or more elements, for example water (H2O). Water is formed by two elements, the element of hydrogen and oxygen. The material has mass, including hydrogen and oxygen. How do we know the mass of hydrogen and oxygen elements present in water? A French chemist named Joseph Louis Proust (1754-1826) tried to combine hydrogen and oxygen to form water.

The hydrogen mass is reacted	Oxygen mass is reacted	Water mass formed	Residual hydrogen or oxygen
1 2 1 2	8 8 9 16	9 9 9 18	- 1 g hydrogen 1 g oxygen -

From the table above shows that every 1 g of hydrogen gas reacts with 8 g of oxygen yields 9 g of water. This proves that the mass of hydrogen and the oxygen mass contained in water has a fixed ratio of 1: 8, no matter how much water is formed. From his experiments, Proust proposed his famous theory as the fixed comparative law, which reads:

"The mass ratio of the elemental elements in the compound is always fixed"

C.    The Law of Multiple Comparisons (Dalton's Law)

The chemical composition is represented by the chemical formula. In compounds, like water, two elements combine and each contribute a number of atoms certain to form a compound. From two elements can be formed several compounds with different comparisons. For example, sulfur with oxygen can form SO₂ and SO₃ compounds. From the elements of hydrogen and oxygen can be formed compounds H₂O and H₂O₂.
Dalton investigated the comparison of these elements in each compound and obtained a pattern of order. The pattern is expressed as a law of multiple comparison which reads:

"When two elements can form more than one compound, the mass of one element remains (equal) then the ratio of the mass of the other elements in the compounds is an integer and simple".

 

D.    Comparative Law of Volume (Gay Lussac)

At first scientists discovered that hydrogen gas can react with oxygen gas to form water. Comparison of the volume of hydrogen and oxygen gas in the reaction remained, ie 2: 1. Then in 1808, French scientist Joseph Louis Gay Lussac successfully experimented on the volume of gases involved in various reactions using various gases.
Here is the data from the experiments performed.

Trial	Volume of oxygen gas produced	The volume of hydrogen gas produced	Volume of water vapor produced
1 2 3	1 2 3	2 4 6	2 4 6

 According to Gay Lussac, 2 volumes of hydrogen gas react with 1 volume of oxygen gas to form 2 volumes of water vapor. In the vapor-forming reaction, for a perfect reaction, for every 2 volumes of hydrogen gas it takes 1 volume of oxygen gas, producing 2 volumes of water vapor. The comparative law of volume reads:

"All gases reacted with the reaction product, measured at the same temperature and pressure." 

2.                  CONCEPT MOL

1.     Atomic Mass and Relative Molecule

The mass of an ato or molecule is too small if expressed in units of grams. For that used the term relative mass. The relative mass of an atom, molecule or ion is obtained by comparing it with 1 mole of carbon-12, 12 C atom.

Relative mass of particles X = mass of particles X / mass 1 atom C-12
Or
                 ArX = mass 1 atom X / 1 sma

With,
1 sma = 1/12 x mass 1 atom 12C
Mass 1 atom 12C = 1,660538 x 12-27 kg
Ar = number of abundance isotope x Ar isotope.

2.      Understanding the concept of Mol

To simplify the number of these extraordinarily small particles, the concept of moles is used. Mol represents the unit of quantity of matter. Unit amount of this substance as well as the simplification of the amount of a good. For example, 1 dozen is used to simplify 12 pieces of glassware and 1 ream to declare 500 sheets of paper. This simplification needs to be done because the chemical processes that take place in everyday life involve a very small collection of very small particles. The units of the particles are too difficult to observe.

1 mol = L particles
L = Avogadro Number = 6.02 x 10²³

Thus, the concept of moles is the unit of quantity of matter that expresses the number of particles of matter.

3.      The Concept Formula Mol

Thus, 1 mol of the substance contains 6.02 x 10²³ particles. The relationship between the number of moles and the number of particles can be formulated as follows:

Number of moles of X (n) = number of particles X / L
or
Number of particles X = n x L

The Avogadro (L) number was discovered by Johann Loschmidt in 1865. The name Avogadro was chosen as a tribute to Avogadro because he was the first to propose the need for a unit of particle count. The name Loschmidt is immortalized as a symbol of that number, L.

The value of the Avogadro number is L = 6.02 x 10²³. Can you imagine the magnitude of that number? Had it collected 6.02 x 10²³ rice grains, the rice could be dumped on the surface of the Australian continent with a height of one kilometer! Or, if an atom is the size of a marble and spread on the surface of the earth, the entire surface of the earth will be covered with marbles with a layer thickness of 80 km! This enormous number is chosen to express the number of atoms because of their practicality and precision. Imagine, it would be complicated if the number of atoms expressed in units of grains, dozen, gross, kodi, or other units.

Avogadro number is special because it menguhungkan unit grams with sma. For example, 6.02 x 10²³ C-12 atoms have a mass of 12 grams. You notice, the number 12 grams is equivalent to the mass of a real atom C-12 is 12 sma. This is the essence of the mole concept proposed by Avogadro.

Here is an example of using Avogadro numbers in chemical calculations.

The perfect combustion reaction produces carbon dioxide (CO₂) gas. If in one day an average bus releases 1 mole of CO₂ in its emissions, how many atoms of CO₂ the bus releases for a week?
Resolution:
The number of moles of CO₂ = 1 mol / day x 7 days = 7 mol
The number of atoms in one molecule of CO₂ = 1 atom C + 2 atoms O = 3 atoms
Number of CO₂ Molecules = 7 x 6.02 x 10²³ molecules = 42.14 x 10²³ molecules

Thus, the number of atoms of CO₂ released = 42.14 x 10²³ molecules x 3 atoms / molecules = 1.26 x 10²⁵ atoms

4.     Relation of Mol, Mass, and Number of Molecules

The value of the relative mass of an element or compound can be used to determine how many moles of the compound are in a given mass. The equations that connect these variables are Mass = mol x Mr

To find out how many particles (atoms / molecules) that menyuusn element or compound is used equation:

Number of particles = mol x Avogadro number
Where the value of avogadro value worth 6.02 x 10²³

Bibliography

https://musnainimusnaini.wordpress.com/kimia-x-2/hukum-dasar-kimia-3/

http://kimiadasar.com/konsep-mol/

http://resagusman.blogspot.co.id/2014/06/stokiometri.html