STOICHIOMETRY

STOICHIOMETRY
(chemical formula, Empirical formula and Molecular formula,reaction equation, Avogadro's Hypothesis)

          Stoichiometry studying quantitative aspects of chemical substances in a reaksikimia, which includes measurements of mass, volume, number of particles of a quantitative scale such as particle involving atoms, molecules, ions, and other microscopic particles

 Basic Laws of Chemistry

1. Gay Lussac Laws (Comparative Law Volume)

Comparison of the volume of gas in accordance with the coefficient of each gas

2. Avogadro's law
The gases at the same temperature and pressure when measured in the same volume have the same number of molecules
3. Lavoisier law
The mass of a substance is the same before and after the reaction is the same

4. Proust Law
Comparison of the mass of the elements in each compound is fixed

5. Dalton Law (Multiple Comparisons) If elements A and B elements form more than one compound, then for a fixed mass of elements A, B of mass elements in the compound compared as integers sederhana.Contoh: In a water molecule (H2O) mass of hydrogen with a mass of oxygen to 1: 8. While dalamhydrogen peroxide (H2O2) mass ratio of hydrogen to oxygen mass 1: 16.

Chemical formula of a compound expressed symbol and atomic number of elements that make up a compound without naming ionic compounds include compounds or covalent. The formula itself is divided into an empirical formula and molecular formula.

                                  Empirical Formula and Molecular Formula

Empirical formula

                 The empirical formula is a formula that states the smallest ratio of the number of atoms that form a compound. For example, ethene compound that has the molecular formula C2H4, the empirical formula of the compound is CH2.

                  In determining the empirical formula to look first is the mass or mass percentage in the compound, and then divided by the relative atomic mass (Ar) of each element. means to determine the empirical formula to look for is the mole ratio of the elements in the compound.

Molecular formula

                  The molecular formula is a chemical formula that states the type and number of atoms that make up a compound. For example: C2H4 (ethene), CO (NH2) 2 (urea) and acetic acid or vinegar (CH3COOH). Molecular formula can be defined as chemical formula stating ratio actual number and type of atoms of a compound.

                From the molecular formula of vinegar is known that the molecular formula C2H4O2 is not written. Some reasons for the molecular formula of vinegar is not written so that

1. To differentiate with other compounds that have the same number of constituent atoms such as methyl formate (HCOOCH3).

2. Molecular formula describes the structure of the molecule. Meaning of the molecular formula we can show the atoms bond together. In the acetic acid molecules of the first C atom binds three atoms of H and 1 atom C and the next C atom binds two O atoms berikunya then 1 O atom binds one atom H.

reaction equations

chemical changes that occur in the material is called a chemical reaction. Chemical reactions can take place in exothermic and endothermic.
Chemical reactions that occur are usually written in the form of the equation. Equation is a statement that expresses or describes a chemical process using a chemical formula. Because it is the writing of the equation must be able to state the actual chemical phenomena, in which the reacting substances and substances of reaction should be portrayed clearly. In order to more clearly note the reaction between hydrogen gas and oxygen gas to form water, which is described as follows:

Numbers preceding formula (2 in H2, 1 at O2 and 2 in H2O) is called the coefficient of the reaction. Reaction coefficient to balance the number of atoms or molecules or ions amounts before and after the reaction.

           In the example above it can be seen that the number of atoms before and after the reaction is the same, it is called the equation equal. Here is the sum:

· The number of H atoms on the left = the number of atoms in the segment H = 4

· The number of O atoms on the left = the number of O atoms in the segment = 2

For certain purposes, other attributes affixed equation. Here are some of the attributes commonly found in persaaman reaction:

· Color substances

· Δ no lower or upper arrows = sign of the warming process

· = Sign equilibrium

· ΔH = enthalpy change prices

· E ° = electrode potential price

The nature of the equation

a. Types of elements before and after the reaction is always the same

b. The number of each atom before and after the reaction is always the same

c. Comparison of the reaction coefficient expressed mole ratio. Special to the comparison coefficients expressed gaseous volume ratio at the same temperature and pressure.

goals and Equalization Reaction Equations

              The purpose of penyetaran equation in order to satisfy the law or the law of conservation of mass Lavoisier and Dalton's atomic theory. Law of mass kekealan reads "mass of matter in a closed system before and after the reaction is fixed" and tori dalton atomic states "in chemical reactions no missing atoms or created but only a rearrangement occurs". This means that the number and type of atoms in chemical reactions are fixed or the same.

               In order for the number and kinds of atoms present in the reactants and products remain so in the equation of each species involved in the chemical reaction given the corresponding coefficients.

                                                                  stoichiometric reactions

Mol relationship with a coefficient of reaction
coefficient of a substance in an equation that states the number of moles of substance. Therefore the number of moles of a substance or substances involved in the mass of a reaction can be determined. Quantitative aspects of the substances involved in the reaction is called reaction stoichiometry. Stoichiometry of this reaction is needed, especially in a number of substances merencanaakan whice would result from a chemical reaction within the industry and in the laboratory.

                     With useful to keep their coefficients of the equation then the number of moles of a substance in the equation are known. Mole of a substance that has been known to be used to determine the mass of substance needed in a reaction. Because it is known as the coefficient of the reaction stoichiometry base reaction.

                  Avogadro's hypothesis and the coefficient of Reaction Volume Relationships

                   In 1811, Ameo Avogadro put forward a hypothesis that says: "the pressure (P) and temperature (T) of the same, the gases have the same volume contains a number of molecules (number of moles) of the same".

This means that the P and T together, the volume ratio of the gases involved in the reaction at a ratio of the number of moles of the substance involved in the reaction. Because of the equation, the coefficient states the number of moles of substances, the volume of gas involved in a reaction similar to the coefficient of the substance.

The relationship between the volume coefficient of a substance can be formulated as follows:

Relative Atomic Mass (Ar)
is the ratio between the mass of 1 atomdengan 1/12 the mass of one atom of carbon 12
Relative Molecular Mass (Mr)
is the ratio between the mass of 1 molekulsenyawa with 1/12 the mass of one atom of carbon 12.Massa relative molecular (Mr) a sum of atomic mass senyawamerupakan constituent elements.

Avogadro's number
1 mole is the amount of the chemical unit numbers of the atoms or molecules of Avogadro's number and mass = Mr compound.
If Avogadro's number = L then:
L = 6.023 x 1023