The Structure of Atom

The structure of an atom is the basic unit of matter consisting of a nucleus and its negatively charged electron cloud surrounding it. The nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in Hydrogen-1 which has no neutrons). The electrons in an atom bound to the nucleus by the electromagnetic force. Similarly, a collection of atoms can bind to each other to form a molecule. Atoms containing the number of protons and electrons of the same neutral, while containing the number of protons and electrons of different positive or negative and is ion. Atoms are grouped based on the number of protons and neutrons in the atomic nucleus. The number of protons in an atom determines the chemical element the atom, and the number of neutrons determine the isotope of the element.
The term atom comes from the Greek, which means it can not be cut or something that can not be divided again. The concept of the atom as a component that can not be divided again was first proposed by the philosophers of India and Greece. In the 17th century and into the 18th, the chemists laid the foundations of this idea by showing that certain substances can not be broken down further using chemical methods. During the late nineteenth century and early twentieth century, physicists have managed to find the structure and subatomic components inside the atom, to prove that the 'atom' is not never be divided again. The principles of quantum mechanics are used The physicists then successfully model the atom.
Relative to daily observations, the atoms are very small objects with masses as minor anyway. Atoms can only be monitored using special equipment such as tunneling microscope Microscopy. More than 99.9% of the mass of the atom is concentrated in the nucleus, the proton and neutron are almost the same mass. Each element has at least one isotope with unstable nuclei that can undergo radioactive decay. This can lead to transmutation that changes the number of protons and neutrons in the nucleus. Electrons are bound to the atom contains a number of energy cedar, or orbital, which is stable and can undergo transitions between these cedar by absorbing or emitting photons that match the energy difference between the levels. The electrons in the atom determines the chemical properties of an element and affect the magnetic properties of the atom.

 Development of Atomic Model

A Greek philosopher named Democritus argued that if an object is cut continuously, then at a given moment will get will get a part that can not be split again. Parts like this by Democritus called atoms. The term atom comes from the Greek "a" which is not, while the "Tomos" which means split. So, it means atoms can not be subdivided. This understanding is then refined into an atom is the smallest part of an element that can not be cut anymore, but yet it still has chemical and physical properties of the object origin.

Atoms denoted by ZXA, where A = mass number (atomic mass indicates, is the number of protons and neutrons), Z = atomic number (indicating the number of electrons or protons). Protons are positively charged, uncharged neutrons (neutral), and negatively charged electrons. The mass of a proton = mass of neutron = 1,800 times the mass of the electron. Atoms that have the same atomic number and different mass numbers are called isotopes, atoms that have the same mass number and atomic number of different so-called isobar, atoms that consists of equal numbers of neutrons called isoton.

 Kinds of Model Atom

Dalton said that atoms like a solid ball or a ball shot put JJ.Thomson say that ATOMM like raisin bread E.Rutherford atom like the solar system suggests
1. John Dalton Atomic Model 

In 1808, John Dalton, who is a teacher in the UK, contemplating on the atom. Results reflection refine Dalton's atomic theory of Democritus. Shadow Dalton and Democritus is that the atoms of solid shape. In Dalton argued postulatnya musings about atoms:
     Each element is composed of extremely small particles called atoms with
     Atoms of the same element the same properties memiliiki
     Atoms of different elements have different properties
     Atoms of an element can not be converted into atoms of another element with the chemical reaction, atoms can not be destroyed and the atoms also can not be destroyed
     Atoms can combine to form atoms called molecules combined
     In the compound, the mass ratio of each element is fixed
Dalton's atomic theory began to arouse interest in the study of atomic models. However, Dalton's atomic theory has shortcomings, which can not explain a solution to conduct electrical current. How could solid ball can conduct electricity when electricity is electrons moving. Meaning there are other particles that can conduct electric current.

 2. J.J. Atom Model Thomson
The downside of Dalton repaired by JJ. Thomson, experiments are done kotoda ray tube. The results of experiments stated there negatively charged particles called electrons in atoms. A ball of solid surface surrounded by electrons and other particles that are positively charged atom is neutral. Thomson model of atom images:

Weakness Thomson models can not explain the arrangement of positive and negative charges within the atomic sphere.

Weakness Thomson atomic model

Thomson's model can not explain the arrangement of positive and negative charges within the atomic sphere.

 3. Rutherford Atom Model
Rutherford conducted a study on α-ray scattering on gold plates. Observations were developed in the Rutherford atomic model hypothesis.
a. Most of the atom is empty surface.
b. Atom has a positively charged nucleus which is the center of mass of the atom.
c. Electrons move around the nucleus at a very high speed.
d. Most of the α particles pass without having distorting / barriers. A small portion deflected, and little is reflected.
Weakness Rutherford Atom Model
a. According to the laws of classical physics, electrons moving around the nucleus emits energy in the form of electromagnetic waves. As a result, the electron eventually it will run out of energy and eventually attached to the core.
b. Rutherford atomic model has not been able to explain where the location of the electron and the way the rotation of the nucleus.
c. Electrons emit energy when moving, so the energy of the atom becomes unstable.
d. Unable to explain the line spectrum of hydrogen atoms (H).

4. Niels Bohr Atom Model
In 1913, Niels Bohr expressed the opinion that the electrons moving around the nucleus in certain paths called shells. [4] Bohr's atomic model is a refinement of the atomic model of Rutherford.
Rutherford's atomic theory weaknesses corrected by Neils Bohr to postulate Bohr:
a. Electrons surrounding the nucleus has a certain trajectory and energy.
b. In particular orbital, the electron energy is fixed. The electrons will absorb energy when moving to the outer orbit and will release energy when moving deeper into orbit
Excess Bohr model of the atom
atom consists of a few skins for a transfer of electrons.
Weakness Bohr model of the atom
a. can not explain the Zeeman effect and the effect Strack.
b. Unable to explain the events of the chemical bond well, the influence of magnetic fields on atoms and atomic electron spectrum more.

Know Experiments Atomic Structure

1. electron
Cathode ray tube experiment was first performed by William Crookes (1875). Results with experiments is found that a beam of light emerging from the cathode into the anode called cathode rays.
George Johnstone Stoney (1891) proposed the name cathode rays yand called "electrons". The downside of stoney can not account for the effect of the differences in the properties of electrons between atoms of an element with atoms in the other elements. Antonine Henri
Beecqerel (1896) found that the light emitted from radioaktof elements that are similar to electrons.
Joseph John Thomson (1897) continued experimentation William Crookes, namely the influence of an electric field and a magnetic field in the cathode ray tube.

The experimental results JJ Thomson showed that cathode rays could be deflected toward the positive pole of the electric field. This proves there is a negatively charged particles in an atom.
The amount of the charge in eletron discovered by Robert Andreww have (1908) through ownership Oil drops trial. 

 Oil sprayed into the tube charged litrik. Due to an attractive force of gravity would precipitate the fall of oil droplets. if the droplet
oil given the negative charge will be attracted to the positive pole electric field. From the experimental results obtained ownership and Thomson electron charge and mass of the electron-1 0.

2. proton
If the mass of the electron 0 shall mean a particle has no mass. But in fact it has a mass of particulate matter that can be measured and the atoms are neutral atoms. Eugene Goldstein (1886) conducted experiments from the gas cylinder that has a cathode, which was given the holes and electric charge.
The experimental results prove that formed when electrons toward the anode, also formed a positive light towards the opposite direction through the hole in the cathode. After trying various gases in the tube, the gas turns hidrogenlah that produces beams of the smallest positive charge both mass and muatanya, so that particles called protons. The mass of a proton = 1 sma (atomic mass units) and the proton charge = +1

3. The nucleus
After the discovery of the proton and electron, Ernest Rutherford conducted a study of gold thin arduous shooting. If the atom consists of a positively charged particles and negatively the alpha rays are fired should not be forwarded / pierce plate so mincullah terms of atomic nuclei. Ernest Rutherford assisted by Hans Geiger and Ernest Marsden (1911) found the nucleus concept is supported by the discovery of X-rays by WC. Rontgen (1895) and the discovery of radioactive substances (1896).

The results of this experiment make Rutherford stated hypothesis that the atom consists of a positively charged nucleus surrounded by negatively charged electrons, so the atom is neutral. The mass of the nucleus is not equal to the mass of protons in the atomic nucleus, so that DAPT predicted that there is another particle in the nucleus of an atom.

 4. neutron
Prediction of triggering W. Rutherford Bothe and H. Becker (1930) conducted experiments on atomic nuclei particle bombardment of beryllium (Be) and the resulting high penetrating power of radiation particles.
James Chadwick (1932). It turns out the particles that cause the high penetrating power of radiation is nertal or uncharged and almost equal to the proton mass. These particles called neutrons and denoted.

Determining Atomic Structure Based on the Periodic Table

1. Drafting Basic Atomic Particles
Atom is the smallest part of an element that still has the properties of that element. The atomic structure describes how the particles in atoms are composed, made ​​up of atoms and atomic nuclei surrounded by electrons scattered in the skin-skin. Can systematically described subatomic particles following.

Most of the atom consists of a vacuum chamber where there is a very small nucleus where mass and positive charge centered and surrounded by electrons are negatively charged. The nucleus is made ​​up of a number of protons and neutrons. The number of protons in the nucleus determines the atomic nuclear charge, while the atomic mass of the core is determined by the number of protons and neutrons. The next three sub-atomic particles (protons, neutrons, and electrons) view of a particular combination of atoms forming the symbol of an element can be written:
X: the symbol of an element
Z: atomic number
A: mass number

 2. Understanding the Structure of An Atom         Look at the number of the periodic table. The atomic number is always smaller than the number of mass labih
         The atomic number is the number of protons. Because of the nature of a neutral atom, the atomic number is also the number of electrons
         Arrangement of electrons in energy levels, always fill the deepest level before filling the outer level
Two things are important to note if you look at the periodic table arrangement daam.
     The number of levels of the outer electrons (or outer shell) is the same as the group number (except helium which has two electrons. Commonly called the noble gases golonga 0 instead of class 8). This applies throughout the group elements in the periodic table (except for the transition elements). So, if you know that barium is in group 2, bearti have 2 electrons in barium teluar level.
     Noble gases have electrons in its outer level

Atomic Number and Mass Number
An atom has a mass of distinctive nature and each other. With the discovery of subatomic particles known term atomic number (Z) and mass number (A)
Writing equalizes wave of atoms of element atomic number and mass number.
where:
A = mass number
Z = atomic number
X = symbol elemen
Mass Number (A) = number of protons + number of neutrons
or Number of neutrons = mass number - atomic number  

Atomic number (Z) = number of protons

1. Atomic number (Z)
Atomic number (Z) shows the number of protons (positive charge) or the number of electrons in the atom. The atomic number is characteristic of an element. Because atoms are neutral, the number of protons equal to the number elektronya, so the atomic number also showed the number of electrons. Electron is what will most determine the properties of an element. The atomic number is written slightly downward before the element symbol

2. Mass Number (A)
Electron mass is very small and is considered zero and the mass of the atom is determined by the nucleus of protons and neutrons. The mass number (A) specifies the number of protons and neutrons that make up the nucleus of an atom of an element. The mass number is written slightly upwards before the symbol of the element.

Isotopes, Isobar, and Isoton an element

1. isotope
Isotopes are atoms that have the same number but have different mass numbers
Each isotope of an element have the same chemical properties as the number of valence electrons equal.
Isotopes can be used to determine the relative atomic mass (Ar) atom is based on the isotope abundances and atomic mass of all isotopes

2. Isobar
Isobar is the elements that have an atomic number but different mass numbers together.

3. Isoton
The atoms are different but have the same number of neutrons

Determining Valence Electrons

1. Electron configuration
Configuration (arrangement) of electrons of an atom by atom shells. Each atom can be charged a maximum eletron 2N2, where n is the location of the skin.
Coat the skin starts from the K, L, M, N and so starting from the closest to the nucleus.
Electrons arranged in such a way on their own skins and stuffed maximum capacity of the skin suit. So there is the rest of their electrons can not be accommodated on the skin then placed next to the skin.

2. Valence electrons
Electrons are involved in chemical bond formation reactions and chemical reactions are electrons in the outer shell or valence electrons.
The number of valence electrons of an atom is determined by the electrons contained in the last shell electron configuration of the atom. Note the table to determine the number of valence electrons

The elements that have the same number of valence electrons will have the same chemical properties as well.

 

Enthalpy and enthalpy change (ΔH)

Enthalpy (H) is the amount of energy that the system at a constant pressure. Enthalpy (H) is defined as the amount of energy contained in the system (E) and work (W).
H = E + W
with:
W = P × V
E = energy (joules)
W = work system (joules)
V = volume (liters)
P = pressure (atm)
The law of conservation of energy explains that energy can not be created and can not be destroyed, but can only be converted from one form of energy into another form of energy. Energy value of the material can not be measured, which can be measured is the change in energy (ΔE). Similarly, the enthalpy, enthalpy can not be measured, we can only measure changes in enthalpy (ΔH).
ΔH = Hp - Hr
with:
ΔH = change in enthalpy
Hp = enthalpy of products
Hr = enthalpy of the reactants or reagents
a. If the product H> H reactants, then ΔH is positive, it means that the absorption of heat from the environment to the system.
b. When the reactant H> H products, then ΔH are negative, meaning the release of heat from the system to the environment.
 
 Mathematically, enthalpy change (ΔH) can be derived as follows.
H = E + W (1)
At constant pressure:
ΔH = ΔE + PΔV (2)
ΔE = q + W (3)
Wsistem =-PV (4)
Substitution of equation (3) and (4) in equation (2):
H = (q + W) + PΔV
H = (q - PΔV) + PΔV
H = q
Thus, at a constant pressure, the change in enthalpy (ΔH) is equal to the heat (q) absorbed or released (James E. Brady, 1990).
Various kinds of chemical reactions based on the heat released / absorbed heat (Martin S. Silberberg, 2000):
a. Chemical reactions that require or absorb heat are called endothermic reactions.
example:
Termination reaction bonding in the molecule H2 elements are:
H2 → 2 H + a kJ ΔH =+aKJ
Endothermic reaction with ΔH is positive (+).
b. The chemical reaction that liberates heat is called an exothermic reaction.
example:
Bond formation reactions at the molecular elements of H2 are:
2H → H2 kJ ΔH =-aKJ
Exothermic reaction with ΔH marked (-).
Diagram enthalpy (energy level diagram)


 The kind of enthalpy change
 The magnitude of the change in enthalpy of a reaction depends on the amount of a substance that reacts, states of matter, temperature, and pressure, the enthalpy change is calculated based on the standard state is the state at standard temperature and pressure at a temperature of 250C (2980 K) and a pressure of 1 atm. Enthalpy change of the reaction was in the form of changes in enthalpy of formation (DHf0), enthalpy change of decomposition (DHd0), enthalpy change of combustion (DHc0), and the enthalpy change of neutralization (DHn0).

a. Standard enthalpy change of formation (DHf0)

Standard enthalpy change of formation, (DHf0) of a substance is the enthalpy change that occurs in the formation of one mole of a substance from its elements measured at standard conditions.
example:
1) Changes in enthalpy of formation of AgCl is the enthalpy change of the reaction:


























 2) Changes KMnO4 enthalpy of formation is the enthalpy change of the reaction:





 DHf0 depend on the states of matter produced, for example:
 ]
 DHf0 water in liquid form in contrast to DHf0 water in the solid state. Under the agreement, DHf0 element = 0 at all temperatures, for example:
 
 b. Standard enthalpy change of decomposition DHd0

Standard enthalpy change of decomposition is the reverse of the enthalpy change of formation. DHd0 a substance is the enthalpy change that occurs in the decomposition reaction of one mole of a substance into the elements in the standard state.

example:


 Marquis de Laplace of France's research found that the amount of heat released in the formation of a compound from its elements equal to the amount of heat required in the decomposition of the compound into its elements. This statement is known as the Law of Laplace.

example:

 c. Enthalpy change of Combustion DHc0

Enthalpy change of combustion, 􀀨 Hc is the enthalpy change that occurs in the combustion of 1 mole of an element or compound at standard conditions.
example:




 d. Enthalpy change of Neutralization DHn0

Enthalpy change of neutralization is the enthalpy change that occurs during the reaction between an acid with a base either by moles per mole of acid or base.

example:

 

Stoichiometry

The term stoichiometry is derived from the Greek meaning stoicheon element and metron meaning measure. Thus, the stoichiometry is the study of the quantitative relationship between reactants and products in the reaction. Stoichiometry can also be said as a matter of chemistry.Have you ever noticed how chemical reactions take place? By the time you held a practicum in the laboratory (Laboratory of Analytical, Inorganic and Physical Science Faculty UNMUL. Lho kok Lab names carry it anyway ... hehe?), In the form of what chemicals are reacted? In general, a chemical reaction takes place in solution. Before you reacting solution, of course you would calculate in advance how many agents will be treated and how much substance to be produced. In the chemistry that is studied in solution stoichiometry.To understand the concept of stoichiometry of the solution, it must first understand the types of reactions in an electrolyte solution, the sense of concentration, mole concept, and the equation.
A. Reactions in Solution ElectrolytesDo you still remember about a solution that can conduct electric current? Called the solution is the solution? The reaction taking place in the solution is the ionization reaction. The solution is an electrolyte solution. Electrolyte solutions are classified into two kinds of weak electrolyte solutions and strong electrolyte solutions.The reaction between the ions in the electrolyte solution can generate covalent compounds, sludge, gas, or discoloration of the solution.1. Acid base neutralization reactionThe reaction between acid and alkaline compounds can produce mineral salts and waterAcid base + salt + H2O ↔Example:KOH (aq) + HCl (aq) KCl (aq) + H2O (1)Mg (OH) 2 (aq) + H2SO4 (aq) MgSO4 + 2 H2O (1)
The reaction between acids and bases commonly called neutralization reaction. However, not all salt produced from this reaction is neutral. There are salts that have acidic or alkaline properties. This depends on a strong or weak acids and bases react to form it.Strong acid + strong base → salt neutralStrong acid + base → salt weakly acidicweak acid + strong base → salt is alkalineThe concentration of acid or base solution can be determined based on the reactions that occur in the solution. This method is known as the acid-base titration. Titration experiments performed by adding acid or base solution of known concentration (a standard solution) to a solution of acid or base to known concentration. The addition continued until the equivalent point is reached, the point at which acids and bases react right out. If the volume of the standard solution and the sample solution is known, the concentration of the sample solution can be determined.
2. Oxide Reaction with Acid TongueAlkaline oxides react with acids to form salts and waterOxides of acid + base → salt + H2OExample:K2O (s) + H2SO4 (aq) → K2SO4 (aq) + H2O (1)
3. Acid Oxide Reaction with BasesThe reaction between oxides asama with bases to form salts and waterOxide acid + base → salt + H2OExample

4. Precipitation ReactionSome of cations and anions in the electrolyte solution to form a solution of poorly soluble in waterExample:

5. Reactions that Produce GasReaction abebrapa acid solution with metal to produce hydrogen gas.Metal oxide + acid → salt + H2Example:

Metal can react with acidic metal on the left side of hydrogen atoms on the following voltaic series:

B. Stoichiometric solutionMost chemical reactions can take place more quickly if the reactants in solution form. Why is that? What distinguishes the chemical reactions in solution (homogeneous mixture) with a heterogeneous mixture? Before discussion of the stoichiometric solution then we will discuss first about the concentration of the solution.

1. Concentration
a. Definition of ConcentrationConcentration is a general term to indicate the number of parts of the solute and solvent present in the solution. Concentration can be expressed quantitatively as well as qualitatively. For a qualitative measure, the concentration of the solution expressed in terms of a concentrated solution (concentrated) and liquid (dilute). The term second states the relative solute and solvent in the solution. Concentrated solution means that a relatively large amount of solute, while the mean number of aqueous solutes are relatively few. Typically, the terms concentrated and dilute concentrations used to compare two or more solutions.In a quantitative measure, the concentration of the solution expressed in g / mL (the same as the units for density). However, the stoichiometry calculations grams replaced with units of moles to obtain units of mol / L. Concentration in mol / L or mmol / mL known as molarity or molar concentration.b. MolarityMolarity or kernolaran stating the number of moles of solute (n) in one liter of solution (L) or millimoles of solute (n) in any one milliliter of solution (mL).

Description: W = weight of substance (g)Mr = period of relative molecular substancesV = volume of solution (mL)
A solution can be prepared by dissolving the solute from the dilute solution murniatau pekatnya: To be more clear, consider the following example:
1) Determination of Molarity by Dilution MethodIf we want to make a 250 mL solution of 0.25 M K2CrO4 from the crystalline form, the way is to calculate the mass of the substance to be dissolved.mol K2CrO4 = 250 mL x 0.25 M= 0.0625 molg K2CrO4 = 0.0625 mol x 194 g / mol= 12.125 gSo, the thing to do is dissolve 12.125 g K2CrO4 crystals into 250 mL of water
2) Determination of Molarity by Dilution MethodIf the solution above will be converted into 0.01 M K2CrO4 concentration, the way is by way of dilution. In dilution we will change the volume and kemolaran solution, but does not change the number of moles of solute.nl = n2 → n = MV↓M1 V1 = M2V2
Description:M1 = concentration before dilutionV1 = volume before dilutionM2 = concentration after dilutionV2 = volume after dilution
For the above example, we can take 10 mL of 0.25 M K2CrO4 After that, the dilution calculation:M1V1 = M2V20.25 M x 10ml = 0.01 MxV2
 = 250 mL
So, the thing to do is dilute 10 mL of 0.25 M K2CrO4 up the volume to 250 mL.If the two types of solutions are mixed and the number of moles of solute change (n1 does not equal n2), then the moles of the substance after mixed depending on the numbernl and n2, while the volume of the solution to V1 + V2.

In the laboratory, concentrated solutions of unknown molarity, but it is known (can be read on the bottle label) is the level (in weight percent) and density (g / mL). How to make a solution with a specific molarity of concentrated solution? The principle is the same as the dilution method. For example, the manufacture of 100 mL of 0.1 M perchloric acid solution of perchloric acid with etiquette: levels of 70% and a density of 1.664 g / mL. The trick is to find the molarity of concentrated solution first. To obtain the value of M, then we have to change the content (%) to convert moles and mass (g) to volume (mL).

 = 11.59 M HClO4
From the above examples can be derived formula:Molarity (M) = Percent weight x Density x 10 / Mr
After molarity is known, then that should be taken (V1). In this case, the volume HC1O4 be taken isM1 V1 = M2 V2V1 x 11.59 M = 100 mL x 0.1M V1 = 0.863 mL
A total of 0.863 mL 11.59 M HC1O4 put pint-sized 100 mL flask, then add distilled water to the 100 mL mark and digojog until homogeneous. Now HC1O4 solution obtained by 100 mL of 0.1 M
2. Chemical Calculations
a. Mol and Reaction EquationsIn class X you have learned about the concept of the mole. On this subject, you will learn the concept of the mole and an integrated equation. We have discovered that one mole of a substance contains 6.02 x 1023 particles of the compound. If applied to an atom or molecule, then:1 mole = 6.02 x 1023 atoms / moleculesTo remind the relationship between the concept of moles by the number of particles, the mass of the atom / molecule, the standard volume and molarity, note the diagram "Mol Bridge" below!

The chart above shows that the mole ¬ able to bridge the various parameters that allow us to understand a chemical reaction.On the chart, it was shown that all paths leading to the mole using a "division", while the path out of the mole using the "multiplication", except for the molarity (M).For example, consider the following reaction?H2 (g) + O2 (g) - H2O (g)The reaction shows that the number of oxygen atoms in the reactants are two pieces, while the amount of oxygen in the product there is a fruit. This is different from the H atom is the same. Therefore, the reaction must be synchronized.Equalization of the reaction can be done by making the coefficient of O2 = ½ so that by the following equation.H2 (g) + ½ O2 (g) - H2O (g)In the above reaction the number of atoms on the reactant O to H is equivalent to the number of atoms of O and H on the product. Fractional number in the equation can be removed by multiplying two coefficients of all reactions.2H2 (g) + O2 (g) 2H2O (g)The above equation shows that the reaction coefficient respectively for H2, 02, and H2O is 2, 1, and 2. In the calculation of chemical reaction coefficient represents the ratio of moles of the substance in the reactants and products of a reaction. That is, the mole ratio in the reaction above, between H2, 02, and H2O is 2: 1: 2.Consider the illustration below!2H2 (g) + O2 (g) ---------------- 2H2O (g)Mole ratio of 2: 1: 2

Another example is the combustion of methane gas in the air.------------------------ methane + oxygen carbon dioxide + waterCH4 + 202 ---------- ------------- CO2 + 2H20


Equation shows that 1 mole of CH4 reacts with 2 moles of O2 to produce 1 mole of CO2 and 2 moles of H2O.From the equation we can say that:The number of moles of H2O produced = 2The number of moles of CH4 in action 1This comparison can be used to calculate the mass of water produced when burning a certain amount of methane in the air.b. Reaction Mass Calculation AgentIf you want to do a reaction in the laboratory, you would measure the reagents in units of grams or liters before rnereaksikannya. Therefore, work in the laboratory will always be associated with the mass calculation.Determination of the number of products and reactants involved in the reaction must be calculated in units of mol. That is, the unit-¬ units known to be changed into the form of a mole. The method is often used in chemical calculations is called the method of approach mol.Step-by-step method mole approach can be seen in the following steps.1. Give the equation of the matter in question, and then synchronized.2. Change all the known units of each substance into moles3. Use coefficients to balance the number of moles of reaction reactant substances and products.4. Change units of moles of substance in question into the unit in question.

C. Neutralization Reaction1. Titration ProcessOne application is the solution stoichiometry calculations find molarity or concentration of a substance in the sample solution through a process called volumetric analysis. Volumetric analysis is a quantitative chemical analysis is done by measuring the volume of a standard solution appropriate to react (react perfectly) with the solution being analyzed. For example, to search for the solution molarity Z, then Z is added to a solution of the standard solution resulting in complete reaction between the solution Z with standar.Larutan standard solution is a solution of the concentration or molarity standard pasti.Larutan have known there are 2 kinds, namely primary standard solution and secondary standard solution. Primary standard solution is a solution of the following standards are made, can be directly used to add to the concentration of the solution to be sought. Secondary standard solution standard solution after it is created can not be directly used, but must be checked again molarity concentration or by adding a solution of a primary standard. The process of checking the secondary standard solution with a solution of a primary standard is called standardization.The process of adding a standard solution to a solution of Z (which will be determined concentration) is called titration. This made the process of adding little by little (drop by drop) using an instrument called burette. Every single drop of standard solution out of the burette volume ± 20 mL. Substance to be titrated is placed in erlenmeyer.At the completion of the reaction between a standard solution with a solution called endpoint analyzed. At this point reached, the titration is stopped.In volumetric analysis, the reaction between the standard solution with the solution being analyzed must meet several requirements, among others:1. Chemical reactions that occur should be simple and straightforward equation written.2. Reactions should be able to run fast. Last drop of standard solution must be able to demonstrate complete reaction. If not, there will be mistakes titration.3. At the completion of the reaction (endpoint) is reached, there must of change in physical or chemical properties that can be observed or indication of changes can be detected by adding a solution of the indicator into the solution to be titrated or can be caused by the color of the solution own standards.For example, the neutralization reaction of NaOH solution with HC1 solution. Neither solution of NaOH or HC1 is the clear solution. The results of the reaction (NaCl and H20), is also the clear, so the endpoint can not be observed. To that end, in the titrated solution (NaOH), was added a solution of indicators, such as phenolphthalein indicator, abbreviated (pp) is an indicator that in alkaline solution gives red color in acidic solution is colorless. The addition of these indicators using a Pasteur pipette. The number of indicator solution were added just one or two drops. Titration of NaOH with HC1 using pp indicators and endpoint is reached when the last drop addition of HCl solution gives discoloration.

 2. Titration Acids BasesOne application of the concept of neutralization reaction is the acid-base titration. In acid-base titration, the value of the equilibrium constant of ionization used as a benchmark for determining the pH of the solution while achieving equivalent point. Equivalent point or end point is when the theoretical amount of acid or base added exactly equivalent stoichiometric with the amount of base or acid in the solution • analyzed.The formula can be used to determine the concentration of the sample solution is as follows:= Sample standard mol molMsampel Vsampel = Mstandar Vstandar