Understanding Stoichiometry
Stoichiometry comes from two Greek syllables Stoicheion meaning "element" and Metron which means "measurement".
Stoichiometry is a subject in chemistry involving the linkage of reactants and products in a chemical reaction to determine the quantity of each reacting agent.
Stoichiometry is a subject in chemistry that studies the quantity of matter in a chemical reaction.
Stoichiometry comes from two Greek syllables Stoicheion meaning "element" and Metron which means "measurement".
Stoichiometry is a subject in chemistry involving the linkage of reactants and products in a chemical reaction to determine the quantity of each reacting agent.
Stoichiometry is a subject in chemistry that studies the quantity of matter in a chemical reaction.
If there is a chemical reaction, you may want to
know how many substances the reaction results? Or
if you want to do a chemical reaction to produce a certain amount of product,
then you have to adjust how many reactants in the reaction. These are all
discussed in stoichiometry.
Before performing Stoichiometric calculations, the equation of the reaction we have must be equalized first.
Equalization of Chemical Reaction
Chemical reactions are often written in bentu equations using element symbols. The reactants are the substances that are on the left, and the product is the substance that is on the right, then both are separated by arrows (can be one or two alternating arrows). Example:
2Na (s) + HCl (aq) → 2NaCl (aq) + H2 (g)
The equation of a chemical reaction is like a prescription in the reaction, thus indicating everything associated with the reaction, whether it is an ion, an element, a compound, a reactant or a product. All.
Then as in the recipe, there is a proportion of the equation shown in the figures in front of the molecular formula.
When considered again, the number of H atoms on the reactant (left) is not equal to the number of H atoms on the product (right). Then this reaction needs to be synchronized. The equalization of chemical reactions must satisfy some chemical laws of matter.
1. The Law of Conservation of Mass
Sound Mass Law Mass: The mass of the product is equal to the mass of the reactants
2. Fixed Comparative Law (Proust Law)
Fixed Comparative Law Sound: The chemical compound consists of chemical elements with the ratio of the elemental masses which remain the same.
3. The Law of Multiple Comparisons (Dalton's Law)
The Law of Multiple Comparisons: If an element reacts with other elements, then the weight ratio of the element is a simple integer.
Before performing Stoichiometric calculations, the equation of the reaction we have must be equalized first.
Equalization of Chemical Reaction
Chemical reactions are often written in bentu equations using element symbols. The reactants are the substances that are on the left, and the product is the substance that is on the right, then both are separated by arrows (can be one or two alternating arrows). Example:
2Na (s) + HCl (aq) → 2NaCl (aq) + H2 (g)
The equation of a chemical reaction is like a prescription in the reaction, thus indicating everything associated with the reaction, whether it is an ion, an element, a compound, a reactant or a product. All.
Then as in the recipe, there is a proportion of the equation shown in the figures in front of the molecular formula.
When considered again, the number of H atoms on the reactant (left) is not equal to the number of H atoms on the product (right). Then this reaction needs to be synchronized. The equalization of chemical reactions must satisfy some chemical laws of matter.
1. The Law of Conservation of Mass
Sound Mass Law Mass: The mass of the product is equal to the mass of the reactants
2. Fixed Comparative Law (Proust Law)
Fixed Comparative Law Sound: The chemical compound consists of chemical elements with the ratio of the elemental masses which remain the same.
3. The Law of Multiple Comparisons (Dalton's Law)
The Law of Multiple Comparisons: If an element reacts with other elements, then the weight ratio of the element is a simple integer.
Stoichiometry,
better known as a chemical count, is the most important basic concept that must
be mastered by a teacher and student.
Some important notes to keep in mind are:
1. To change a mass mass mass into volume or vice versa, we must change it to mole first (hence called terminal mole)
2. From mass quantity, STP gas volume, and the number of particles if converted to mole of operation we use is divide, whereas from mol to mass, gas volume STP, and the number of particle operation we use is multiplication.
3. The number of 22.4 L obtained from the volume of 1 mole of gas at STP (0O C and 1 atm) by using the ideal gas formula PV = nRT
4. If gas conditions are not STP, ie there are 2 possibilities:
A. In certain T and P, then enter into the formula PV = nRT
B. In the same condition as another gas, locate the other gas volume under such conditions
5. The number of particles can be the number of molecules, can also the number of atoms,
For example: if the Avogadro number is N, at 4 grams NaOH (Mr = 40)
A. How many molecules
B. How many atoms
Solution 4 grams NaOH = 0.1 mol NaOH, means:
A. Number of molecules NaOH = 0.1 N
B. Number of atoms = (0.1 Mol Na + 0.1 mol O + 0.1 mol H) N = 0.3 N
Some important notes to keep in mind are:
1. To change a mass mass mass into volume or vice versa, we must change it to mole first (hence called terminal mole)
2. From mass quantity, STP gas volume, and the number of particles if converted to mole of operation we use is divide, whereas from mol to mass, gas volume STP, and the number of particle operation we use is multiplication.
3. The number of 22.4 L obtained from the volume of 1 mole of gas at STP (0O C and 1 atm) by using the ideal gas formula PV = nRT
4. If gas conditions are not STP, ie there are 2 possibilities:
A. In certain T and P, then enter into the formula PV = nRT
B. In the same condition as another gas, locate the other gas volume under such conditions
5. The number of particles can be the number of molecules, can also the number of atoms,
For example: if the Avogadro number is N, at 4 grams NaOH (Mr = 40)
A. How many molecules
B. How many atoms
Solution 4 grams NaOH = 0.1 mol NaOH, means:
A. Number of molecules NaOH = 0.1 N
B. Number of atoms = (0.1 Mol Na + 0.1 mol O + 0.1 mol H) N = 0.3 N
2Na (s) + 2HCl (aq) → 2NaCl (aq) + h2 (g)
We can know that 2 moles of HCl react with 2 moles of Na to form 2 moles of NaCl and 1 mole of H2. By equalizing this reaction, it can be known the quantity of each substance involved in the reaction.
Hence the equalization of this reaction is very important in solving stoichiometric problems.
Example:
Lead (IV) Hydroxide reacts with Sulfuric Acid, by reaction as follows:
Pb (OH) 4 + H2SO4 → Pb (SO4) 2 + H2O
If we look good either:
|
Unsur
|
Reaktan
(jumlah mol) |
Product
(jumlah mol) |
|
Pb
|
1
|
1
|
|
O
|
8
|
9
|
|
H
|
6
|
2
|
|
S
|
1
|
2
|
Then this equation is not equivalent. Therefore we need
to equate this equation. In
the reactant there are 16 atoms, but in its product there are only 14 atoms. This
equation needs to add coefficients so that the number of atoms of the elements
is the same.
In front of H2SO4 it is necessary to add coefficient 2 so that the number of sulfur atoms corresponds, then in front of H2O it is necessary to add coefficient 4 so that the number of oxygen atoms is appropriate. Then the equivalent reaction is:
Pb (OH) 4 + 2H2SO4 → Pb (SO4) 2 + 4H2O
In front of H2SO4 it is necessary to add coefficient 2 so that the number of sulfur atoms corresponds, then in front of H2O it is necessary to add coefficient 4 so that the number of oxygen atoms is appropriate. Then the equivalent reaction is:
Pb (OH) 4 + 2H2SO4 → Pb (SO4) 2 + 4H2O
|
Unsur
|
Reaktan
(jumlah mol) |
Product
(jumlah mol) |
|
Pb
|
1
|
1
|
|
O
|
12
|
12
|
|
H
|
8
|
8
|
|
S
|
2
|
2
|
The condition in which the equation of the
reaction is equal is when it satisfies the following two criteria:
1. The number of atoms of each element on the left and right sides of the equation has been the same.
2. The number of ions on the left and right has been the same (using redox reaction equation)
Stoichiometric Calculations on Equivalent Chemical Equations
In stoichiometry, an equivalent chemical equation provides information to compare each element in a reaction based on a stoichiometric factor. The stoichiometric factor is the ratio of the moles of each reacting substance / substance.
1. The number of atoms of each element on the left and right sides of the equation has been the same.
2. The number of ions on the left and right has been the same (using redox reaction equation)
Stoichiometric Calculations on Equivalent Chemical Equations
In stoichiometry, an equivalent chemical equation provides information to compare each element in a reaction based on a stoichiometric factor. The stoichiometric factor is the ratio of the moles of each reacting substance / substance.
Understanding Molar Mass
Before performing stoichiometric calculations, we need to know what a molar mass is. The molar mass is the ratio between the mass and moles of an atom.
To know the Molar Mass of an element then we only need to read it in the periodic table of elements. As for knowing the Molar Mass compound we need to calculate it based on the molecular formula of the compound.
Problems example:
Determine Molar Mass from H2O?
Answer: 2 (1.00794g / mol) + 1 (15.9994g / mol) = 18.01528g / mol
The molar mass of Hydrogen is 1.00794g / mol multiplied by 2 because there are two hydrogen atoms in one water compound. Then the molar mass of oxygen is added.
The obtained Molar mass can be used to calculate the mole of a compound.
The formula of the composition of the mole of the compound is: n = gram / Mr
Or n = M x V
Where M = gram / Mr x 1000 / V
Before performing stoichiometric calculations, we need to know what a molar mass is. The molar mass is the ratio between the mass and moles of an atom.
To know the Molar Mass of an element then we only need to read it in the periodic table of elements. As for knowing the Molar Mass compound we need to calculate it based on the molecular formula of the compound.
Problems example:
Determine Molar Mass from H2O?
Answer: 2 (1.00794g / mol) + 1 (15.9994g / mol) = 18.01528g / mol
The molar mass of Hydrogen is 1.00794g / mol multiplied by 2 because there are two hydrogen atoms in one water compound. Then the molar mass of oxygen is added.
The obtained Molar mass can be used to calculate the mole of a compound.
The formula of the composition of the mole of the compound is: n = gram / Mr
Or n = M x V
Where M = gram / Mr x 1000 / V
Example:
1. What is the level of C in 50 grams of CaCO3? (Ar: C = 12; 0 = 16; Ca = 40).
answer :
2. What is the pressure of 0 5 mol of O2 with a volume of 10 liters if at that
temperature 0.5 mole of NH3 has a volume of 5 liters den with 2 atmospheres
pressure?
A:
P1 V1 = P2 V2 then 2 x 5 = P2 x 10 → P2 = 1 atmosphere
3. Calculate the mass of 10 liters of nitrogen gas (N2) if under these
conditions 1 liter of hydrogen gas (H2) mass is 0.1 g.
Given: Ar for H = 1 and N = 14
4. What is the volume of 8.5 grams of ammonia (NH3) at a temperature of 27
degrees C and a pressure of 1 atm? (Ar: H = 1; N = 14).
Answer :
Mol of ammonia = (8,5 / 17) mol = 0,5 mol
Ammonia volume (STP) = 0.5 x 22.4 = 11.2 liters
Based on the Boyle-Gay Lussac equation:
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