Stoichiometry
Two basic materials that must buddy learn before we get into other chemical stoichiometry materials ... what is it? None other than Chemical Reaction And Basic Chemistry. Now let's study the two basic materials one by one.
A. Chemical Reaction
Chemical reaction is a reaction that occurs in elements or chemical compounds that resulted in the formation of a new chemical compound that is different from the reactants.
Chemical reactions are also reactions involving the movement of electrons in the formation and disconnection of chemical bonds.
B. Basic Law of Chemistry "An object will remain silent while there is no force working on it". That is the sound of I Newton's law which is one of the laws we learn in physics. Well, in chemistry there are laws governing the occurrence of a chemical reaction, call it mass conservation law, fixed comparison law, volume comparison law, and Avogadro's law.
1. The Law of Conservation of Mass / Law of lavoiser
As the name implies, this law was discovered by our teacher named Antonie Lavoiser. In his law, he states that "The total mass of matter after reaction and before reaction is the same".
The point of his statement is that "the sum of the mass of a substance acting as a reactant is equal to the sum of the mass of a substance acting as a product".
The point is → Reactant Mass = Mass Product
2. Fixed Comparison Law / Proust Law This law was triggered by our lecturer named Joseph Proust. In this law he states that "Comparison of the mass of the constituent elements of a compound is always fixed".The point of his statement is that "every chemical compound is constituted by elements whose ratio of the mass amount is always fixed. Although we try to react an element with another element whose mass quantity is inconsistent with the comparative provision, the element will not run out" .
3. Law of the Gay / Lussac Volume / Legal Comparison At the same pressure and temperature, the volume of the reacting gas and the gas volume of the reaction product are simple and integer ratios. This is the sound of the law triggered by our legendary scientist named Gay lussac.
4. Avogadro's Law
At the same temperature and pressure, a gas having the same volume also has the same number of particles, This is the statement of the oldest legendary scientist, Mr. Avogadro. The point of his statement is that the amount of particles of a gas is independent of the Mass Or Mr. possessed by the gas, while in the same volume, temperature and pressure, the amount of particles of a gas will always be the same.
Understanding:
Stoichiometry Chemistry is one branch of chemistry that studies about the
quantitative relationship between the amount of reactants with the product.
Understanding Concepts: Stoichiometry
Relative atomic mass (Ar) and mass molecule relative (Mr)
The
relative atomic mass (Ar) is the mass ratio of an atom of an element with a
comparable atom. While the relative molecular mass (Mr) equals the molecular
weight (BM). Formula 
Information : C12 = 1,993 x 10-23 grams
Concepts of Mol and Equation Reactions
Empirical Formula and Molecular Formula Empirical Formula: the formula which states the smallest comparison of atoms of the elements that make up a compound. For example, H 2 O and CH 2 O
Molecular formula: a formula which expresses the number of atoms of the elements that make up a senyawa.Contoh molecule, H 2 O and C 6 H 12 O 6.
While the empirical formula is the simplest form of compound, its molecular formula is a term as it would appear in a chemical equation. The empirical formula and the molecular formula can be the same, or the molecular formula can be a multiple of positive integers of the empirical formula. Example of empirical formula: AgBr, Na2S, C6H10O5. Examples of molecular formulas: P2, C2O4, C6H14S2, H2, C3H9.
One can calculate the empirical formula of the mass or percentage composition of any compound. If we have only mass, all we do is essentially eliminate steps to change from percentage to mass.
Density.
Density refers to the mass per unit volume of a substance.
Would you explain to me, how the relationship of moles to the number of particles and their examples?
BalasHapusThe relationship can be seen from the following statement:
HapusOne mole is the amount of material containing the number Avogadro, N A, approximately 6.022 × 10 23 molecules or atoms. The molecule, in this definition, is understood as the smallest unit that forms the characteristic compound. Initially, the mole is defined as the number of particles whose total mass in grams is numerically equivalent to the atom or molecular weight in units of atomic mass, which is referred to as gram-atom or molecular weight of gram. This is how the value above for N A is calculated. As the ability to make absolute single measurements of atomic and molecular masses has improved, however, modern metrology is predisposed to alter the approach and determine the exact Avogadro number of quantities, thus slightly altering the definition of the atomic mass of the unit and removing the need to determine atomic weights against specific isotope species . The latest and most accurate value for the Avogadro number is 6.0221415 (10) × 10 23 mol -1.
Give me an example of how to determine the molecular formula and the empirical formula of a compound
BalasHapusA hydrocarbon compound comprising 84% carbon and 16% hydrogen. If it is known that the hydrocarbon is 100, determine the molecular formula of the hydrocarbon?
HapusAnswer
Suppose the empirical formula of the hydrocarbon compound is CxHy.
The first step that needs to be done is to configure the unit percent to gram.
Since the mass of the starting substance is unknown then the mass of the substance is considered 100 grams. Therefore, the carbon mass in grams is equal to the% mass
Gram of carbon = 84/100 x 100 grams = 84 grams
Gram hydrogen = 16/100 x 100 = 16 grams
The mole ratio of each element is the value of x and y.
Y: x = gram C / Mr.C: gram H / Mr.H
= 84/12: 16/1
= 7; 16
So the empirical formula of the compound is C7H16.
The molecular formula can be determined with certainty if the relative molecular mass of the compound is known.
(C7H16) n = 100
100n = 100
N = 1
So the molecular formula of the compound is the same as the empirical formula C7H16.
How to measure the moles of atoms and moles of compounds?
BalasHapusMeasurement of mol compounds: molecular mass • CO2 molecular mass?
Hapus1 mole of CO2
1 mol C +2 mol O mass 1 atom C = 12.0 g mass 2atomO
2x16.0 g = 32.0 g total = 44.0 g The molecular mass of CO2 is 44.0 g The mass or weight of 1 mole (mol) of the substance is written in units of gram 1 mole CO2 = 44.0 g 1 mol H2O = 18 , 0 g 1 mol of NH3 = 17.0 g
Mol is the SI base unit that measures the amount of substance. [1] The term "mol" was first coined by Wilhem Ostwald in German in 1893, [2] although there had previously been a concept of equivalent mass a century earlier. The term mole is thought to originate from the German word Molekül. Gram names of atoms and grams of molecules have also been used in the same sense as moles, [1] [3] but are now not used.
One mole is defined as the sum of the substances of a system containing "elementary entities" (atoms, molecules, ions, electrons) as much as atoms in 12 grams of carbon-12. [1] So:
One mole of iron contains an amount of atoms as much as one mole of gold;
One mole of benzene contains a number of molecules as much as one mole of water;
The number of atoms in one mole of iron is equal to the number of molecules in a mole of water.
What underlies the emergence of avogadro's law?
BalasHapusThe emergence of avogadro law began in 1811 Amadeo Avogadro (1776-1956) from the Italian filed which was then called avogadro theory. Why is the ratio of the volume of gases in a reaction a simple number? Many experts including Dalton and Gay Lussac failed to explain the comparative law of volume found by Gay Lussac. Dalton's inability because he considers elemental particles to always be single (monoatomic) atoms. In 1811, Amedeo Avogadro described the Gay Lussac experiment. According to Avogadro, elemental particles are not always single (monoatomic) atoms, but are 2 atom (diatomic) or more (poliatomic).
HapusThe 19th-century physicists had no knowledge of the molecular or atomic period and its size until the turn of the 20th century, after the discovery of electrons by American physicist Robert Andrews Millikan, which carefully determined the charge. This determination, finally, shows the avogadro number accurately, that the number of molecules in the same amount of material weighs the same as the molecule.
This law was discovered by Amedeo Avogadro in 1811. The Avogadro hypothesis states that two ideal gas samples of the same volume, temperature and pressure will contain the same number of molecules. An example is, when hydrogen and nitrogen of the same volume contain the same number of molecules when they are at the same temperature and pressure. Avogadro called particles as molecules.
Can you provide an example of a problem that can be solved using the Law of the Gay / Lussac Volume / Legal Comparison?
BalasHapusAn Example of Gay Lussac's Law or the Comparative Law of Volume
Hapus1.) Into the tube Eudiometer incorporated a gas mixture comprising 26.0 mL of hydrogen gas and 24.0 mL of oxygen gas, and passed an electric spark. What is the volume of residual gas (in mL) what gas?
Resolution:
Hydrogen + oxygen -> water
2 volum: 1 volum: 2 volum
26 mL: 13 ml: 26 mL
The remaining gas is 11 mL of oxygen.
2.) What is the volume of sulfur trioxide gas (SO3 (which is formed when 2 L of sulfur dioxide gas (SO2) reacts perfectly with oxygen gas? Given the volume of reacting gas: 2: 1: 2
Resolution:
2SO2 + O2 -> 2SO3
2 volum: 1 volum: 2 volum
2 L: 1 L: 2 L
So the volume of sulfur trioxide as much as 2 Liters.
Can you explain what is the difference of empirical formula and molecular formula ?. Give an example !
BalasHapus1.) Empirical Formulas
HapusThe empirical formula is the formula which expresses the smallest comparison of atoms of the elements that constitute a compound. The chemical formula of ionic compounds is an empirical formula. For example the empirical formula:
A. Sodium chloride is an ionic compound consisting of Na + ions and Cl- ions with a ratio of 1: 1. The chemical formula of NaCl sodium chloride.
B. Calcium chloride is an ionic compound consisting of Ca2 + ions and Cl- ions with a ratio of 2: 1. Chemical formula of CaCl2 calcium chloride.
In the condition of the room, some of the elements exist that make up the molecules. The chemical formula of such elements is not represented only by its elemental symbol, but the element and the number of atoms that make up the molecule of that element.
Example:
A. Oxygen gas chemical formula is O2, meaning the chemical formula of oxygen gas consists of oxygen molecules constructed by two oxygen atoms.
2.) Molecular Formulas
The molecular formula is a formula that states the number of atoms of elements that make up one molecule of a compound. So the molecular formula represents the actual arrangement of the substance molecule. Example of molecular formula:
A. The formula of water molecules is H2O which means in one water molecule there are two hydrogen atoms and one oxygen atom.
B. C6H12O6 glucose molecule formula which means in one glucose molecule there are 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.