Using English to Calculate
CHEMICAL CALCULATION (STOIKIOMETRY)
In chemistry, stoichiometry
(sometimes called stoichiometry of reaction to distinguish it from composition
stoichiometry) is a science that studies and quantifies quantitative
relationships of reactants and products in chemical reactions (chemical
equations). This word comes from the Greek stoikheion (element) and metriā
(size).
Stoichiometry
is based on the basic laws of chemistry, namely the law of conservation of
mass, the law of fixed comparison, and the law of multiple comparisons.
I. Basic Law Of Chemical Science
A. The Law of Conservation of Mass (Lavoisier's Law)
"The mass of substances before and after the reaction is the same".
Example:
S + O 2 → SO 2
2 gr 32 gr 64 gr
B. Fixed Comparative Law (Proust Law)
"The ratio of the elemental masses in each compound is fixed"
Example:
H 2 O → mass H: mass O = 2: 16 = 1: 8
C. The Law of Multiple Comparisons (Dalton's Law)
"If two elements can form two or more compounds, and the mass of one element is equal,
the ratio of the mass of the second element is proportional to the simple and integer".
Example:
- Element N and O can form NO and NO 2 compounds
- In the NO compound, mass N = mass O = 14: 16
- In the compound NO 2, mass N = mass O = 14: 32
- The ratio of N masses to NO and NO 2 is the same
O = 16: 32 = 1: 2 mass ratio
D. Ideal Gas Law
For an ideal gas or a gas that is considered to be valid applies the formula:
PV = n RTInformation:
P = pressure (atmosphere)
V = volume (liter)
N = mol = gram / Mr
R = gas constant (lt.atm / mol.K)
T = temperature (Kelvin)
From the formula can be obtained:
II. Mass Of Relative Atom And Relative Moleculous Mass
1. Relative
Atomic Mass (Ar)
Experts use the
C-12 carbon isotope as standard with a relative atomic mass of 12. The relative
atomic mass represents the average mass ratio of one atom of an element to 1/12
of the C-12 atomic mass. Or it can be written:
1 unit of
atomic mass (amu) = 1/12 mass 1 atom C-12
2. Relative
Molecular Mass (Mr)
Molecule is a
combination of several elements with a certain ratio. The same elements combine
to form elemental molecules, while different elements form molecules of
compounds. The molecular mass of an element or compound is expressed by a
molecular mass (Mr). The relative molecular mass is the ratio of the molecular
mass of an element or
Compound
against 1/12 x the mass of C-12 atoms.
III. Concept Mol
A. In chemistry the unit of quantity used is mol
B. One mole is a number of substances containing 6.02 x 10 ^ 23 particles
The relationship of Moles to the number of particles
Number of Particles = mol x 6.02 x 10 ^ 23
Mol = Number of particles / 6.02 x 10 ^ 23
Relation of Moles to Mass
For element:
• mol = gram / Ar
• gram = mol x Ar
For compounds:
• mol = gram /
Mr
• gram = mole x
Mr.
Relation of
Mole to Gas Volume
Every mole of
gas of any standard state (0oC, 1 atm) has a volume of: 22.4 liters.
• Volume of gas
= mol x 22.4
• mol = Volume
/ 22.4
The mole
relationship, the number of particles and the gas relation can be represented
in the form
Diagram as
follows:
Would you explain to me how the relationship of moles to the masses and their examples?
BalasHapusFor elements m=n x Ar and n = m : Ar
Hapusfor compound m = n x Mr and n = m : Mr
Problems example
1. Determine the mass of 2 moles of ammonia (Mr. NH3 = 17)
Answer:
M = n x Mr = 2 x 17 = 28 grams
2. Calculate the mole amount of iron with a mass of 28 grams (Ar Fe = 56)
Answer:
N = m / Ar = 28/56 = 0,5 mol
Can you explain the relation of temperature and pressure?
BalasHapusAs far as I know the relationship between these two equations
HapusP1 / T1 = P2 / T2 when volume is constant
Or in an ideal gas equation
PV = nRT where V = gas volume, n = mol of gas, R = common gas constant,
What's the use of molarity?
BalasHapusIn chemistry, molarity (M) is a measure of the concentration of the solution. The molarity of a solution expresses the number of moles of a substance per liter of solution. For example 1.0 liter of solution contains 0.5 mol of X compound, then this solution is called 0.5 molar solution (0.5 M). Generally the concentration of aqueous aqueous solution is expressed in molar units. The advantage of using molar units is the ease of calculation in stoichiometry, since the concentrations are expressed in number of moles (proportional to the number of actual particles). The disadvantage of using this unit is the inaccuracy in the measurement of volume. In addition, the volume of a liquid changes with temperature, so the molarity of the solution can change without adding or reducing any substance. Moreover, in a less dilute solution, the molar volume of the substance itself is a function of concentration, so the molarity-concentration relationship is not linear.
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BalasHapusA mass of one mole of substance equal to the value of Ar (for atoms) or Mr (for compounds). The mass of one mole of substance is called the molar mass (Mm) in units of grams per mole (g mol-1).
HapusAt certain temperatures and pressures, each of the same volume gases contains the same number of molecules. That is, any gas for the same volume and measured on the same P and T will contain the same number of molecules. If the number of gas molecules as much as Avogadro constant (L = 6.02 × 1023 molecules) then it can be said that the amount of gas is one mole.
Please explain the laws that govern the stoichiometry!
BalasHapusStoichiometry rests upon the laws such as law of definite proportion and law of multiple proportions and law of conservation of mass.
HapusLaw of conservation of mass: Using the physical laws such as law of conservation of mass, which states that the mass of the reactants equals the mass of the products, Stoichiometry is used to gather information about the amounts of various elements used in a chemical reaction, and whether they took the form of gases, solids or liquids.
Law of definite proportion: It states that a chemical compound (substance consisting of 2 or more elements) always contains exactly the same proportion of elements (substance with one type of atom) by mass.
Law of multiple proportions: It is one of the basic laws of stoichiometry, along side the law of definite proportions. It is sometimes called as Dalton’s law. It says that, if 2 elements form more than 1 compound between them, then the ratio of the masses of the second element which combine with the fixed mass of the first element will both ratios of small whole number.
there are laws in ideal gas law, what the different of those?
BalasHapusA. Boyle's Law
HapusIf the temperature of the gas within the closed vessel is kept constant, then the gas pressure will be inversely proportional to its volume.
The statement can be written:
PV = constant
P1V1 = P2V2
B. Charles's Law
If the gas pressure in a closed vessel is kept, the volume of the gas is proportional to or proportional to suhuny (absolute)
The statement can be written as follows:
V / T = constant or V1 / T1 = V2 / T2
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BalasHapus1. Relative Atomic Mass (Ar)
HapusExperts use the C-12 carbon isotope as standard with a relative atomic mass of 12. The relative atomic mass represents the average mass ratio of one atom of an element to 1/12 of the C-12 atomic mass. Or it can be written:
1 unit of atomic mass (amu) = 1/12 mass 1 atom C-12
2. Relative Molecular Mass (Mr)
Molecule is a combination of several elements with a certain ratio. The same elements combine to form elemental molecules, while different elements form molecules of compounds. The molecular mass of an element or compound is expressed by a molecular mass (Mr). The relative molecular mass is the ratio of the molecular mass of an element or
Compound against 1/12 x the mass of C-12 atoms.
can you give me example for Relative Atomic Mass (Ar) and Relative Molecular Mass (Mr)?
BalasHapusOkey, example CH4..
HapusCH4 have relatif atomic mass C and H, but CH4 have relative molekuler mass C=1 and H=4
What is the molar difference with molal? Explain by example !!!
BalasHapusMolarity (M)
HapusMolarity expresses the number of moles of solute in every one liter of solution. Molarity is denoted by M notation and the unit is mol / liter. Mathematically formulated as follows:M = n/v
Molality (m)
Molecular or molecular concentration (m) represents the number of moles of solute in 1000 grams of solvent. Mathematically, it can be formulated:Molality = n/ p
Can you explain about concept mol? And give the example
BalasHapusFor element:
Hapus• mol = gram / Ar
• gram = mol x Ar
For compounds:
• mol = gram / Mr
• gram = mole x Mr.
Example:
BalasHapusS + O 2 → SO 2
2 gr 32 gr 64 gr
But, if O2 mass is 46.8 gr and SO2 54gr, how much is mass S?
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BalasHapusOxidation number (Bilox) is the charge of an atom / element in a molecule / compound determined by the difference in the price of electronegativity. Atoms have the ability to receive and release electrons, this ability is measured in the form of oxidation. Bilox can be either positive or negative, so it can also be considered ion charge.
HapusStandard Oxidation Standard Regulations
1. Free element; Oxidation of the element = 0
Example: Na (s), H2 (g), P4 (s), Al (s), Cl2 (g), Br2 (l) each element of oxidation = 0.
2. The ionic element; Biloks the element = the amount of charge.
Example: Na + (aq) biloks Na = + 1, Cl- (aq) biloks Cl = -1, Al3 + (aq) biloks Al = +3.
3. Metal Gol IA (Li, Na, K, Rb, Cs, Fr) in the compound; Biloks the element = +1.
Example: KCl oxidation K = +1.
4. Metal Gol IIA (Be, Mg, Ca, Sr, Ba, Ra) in the compound; Biloks the element = +2.
Example: Ba (OH) 2 oxidation Ba = +2.
5. Metal Gol IIIA (Al, Ga, In, Tl) in the compound; Biloks the element = +3.
Example: Al2 (SO4) 3 biloks Al = +3.
6. Gol Gol VIIA (F, Cl, Br, I, At) in binary compounds (consisting of two types of elements); Biloks the element = -1.
Example: AlCl3 biloks Cl = -1.
7. Hydrogen element when binding to non-Metal; Oxidation H = +1 but when binding to Metals; Biloks H = -1.
Example: HNO3 oxidation H = +1. AlH3 biloks H = -1.
8. Oxygen Elements when in a Peroxide compound; Oxidation O = -1 but when in a non-Peroxide compound; Oxidation O = -2.
Example: H2O2, BaO2 oxidation O = -1, H2O = -2
9. The sum of all oxidation states of the elements that make up the compound = zero
10. The sum of all oxidation states of the elements forming the ion of the atomic group = the amount of charge of the ion.
Can you give examples of stoichiometric roles in each chemical calculation?
BalasHapusPropane burns by reaction equation:
HapusC3H8 + O2 → H2O + CO2
If 200 g of propane is burned, then how much H2O is formed?
Answer:
First: Resolve the equation of the reaction!
C3H8 + 5O2 → 4H2O + 3CO2
Second: Calculate C3H8 mole!
Mol = m / Mr -> mol = 200 g / 44 g / mol -> mol = 4.54 mol
Third: Calculate the ratio of H2O: C3H8 -> 4: 1 (* based on the comparison coefficient on the equation of the reaction)
Kempat: Calculate the moles of H2O by comparison
Mol H2O: 4 = mol C3H8: 1
-> mol H2O: 4 = 4.54 mol: 1
-> mol H2O = 4.54 x 4 = 18.18 mol
Fifth: Convert from mol to gram.
Mol = m / Mr -> m = mol x Mr -> m = 18.18 mol x 18 = 327.27 grams.
if every compound have the Mr, how to find the Mr of the compound?
BalasHapusWhy the electrolyte is divided into 2 parts?
BalasHapus