Stoichiometry
Stoichiometry is the basic chemical calculation that states quantitative relation of chemical formulas and chemical equations. Here are the materials you need to know to understand, from the concept of moles and molar masses, empirical formulas and molecular formulas, basic stoichiometry of solutions and ideal gases, and the writing and equalization of reactions, with examples of problems and discussions.
Molar and Molar Mass Concepts (})
In SI systems, one mole is defined as the sum of the material composed of entities (atoms, molecules, or other particles) a sum of the atoms in 12 grams of carbon-12. The value of the number of atoms is 6.022 × 1023 called the Avogadro number, NA.
See also other material:
Electron-Configuration
Chemical Association
The molar mass,}, is defined as the mass of 1 mol entity (atom, ion, molecule, unit of formula) of matter. The units of the molar mass (}) are grams / mol.
M = n \}
N = nN_A
The concept of stoichiometry Stoichiometric material: The relationship of mass, the number of moles, and the number of atoms of the element
(Source: Chang, Raymond, 2010. Chemistry (10th edition) New York: McGraw Hill)
Empirical Formulas and Molecular Formulas
The empirical formula is the simplest integer ratio of the number of moles of each element in a compound. The molecular formula represents the true number of moles of each element in 1 mole of the compound. The molecular formula may be identical to the empirical formula or an integer multiple of the empirical formula. For example, phosphoric acid (H3PO4) has a molecular formula and an identical empirical formula. Glucose has a molecular formula C6H12O6 which is a folding of 6 times its empirical formula, CH2O.
Molecular formula ≡ (empirical formula) n
} Molecular formula = n ×} empirical formula, n = 1, 2, 3, ...
Basic Stoichiometric Solution
The term "concentration" of the solution expresses the amount of solute dissolved in a certain amount of solvent or a certain amount of solution. The concentration of the solution can be expressed in molarity. Molarity (M) is defined as the number of moles of solute per liter of solution.
M = \ frac {n} {V}
Basic Ideal Gas Stoichiometry
The molar volume, Vm, is defined as the volume of 1 mol entity (atom, ion, molecule, unit of formula) of matter. The unit of the molar volume (Vm) is L / mol.
V_m = \ frac {V} {n}
Avogadro's law states that at certain pressures and temperatures and fixed, the volume of the gas is directly proportional to the amount of gas.
V \ infty n [P, T \: constant]
\ Frac {V} {n} = constants \: [P, T \: constant [/ latex
[latex] V_m = constant \: [P, T \: constant]
In the STP state (P = 1 atm, T = 273 K), Vm ideal gas = 22.414 L / mol
In the case of RTP / ATP (P = 1 atm, T = 298 K), ideal gas Vm = 24 L / mol
In certain circumstances, an ideal gas law applies:
PV = nRT
V_m = \ frac {RT} {P}
Where R is the gas constant, R = 0.08206 L ∙ atm / mol ∙ K = 8.314 J / mol ∙ K
Writing and Equating Chemical Reaction Equations
The chemical reaction equation is a statement written with a molecular formula that provides information on the identity and quantity of substances involved in a chemical or physical change. All the reacting substances, called reactants, are placed to the left of the arrow, whose direction of the arrow to the right refers to the product, ie all the substances resulting from the reaction.
In the equation of the reaction, the reaction coefficient is known, which is the number on the left of the molecular formula for multiplying all the atoms in the molecular formula. The comparison of the reaction coefficients can be interpreted as the mole ratio of the substances in the reaction. In each of the reactants and products, it is written in the form of the substance (s (solid), l (liquid), g (gas), or aq (solution with water solvent)) in brackets to the right of each molecular formula.
Example of equivalent chemical reaction equation:
Equation of reaction
Example of steps equalizing the reaction equation:
1. equalize the equation of the reaction
2. stoichiometric calculations
3. chemical calculations
4. equivalent results
Stoichiometry Reaction
In chemical reactions, the amount of reacting reactants is sometimes incompatible with the stoichiometric amount of the reaction (not in accordance with the coefficient ratio of the equivalent equation). Therefore, there will be reactants that have reacted first compared to other reactants. The reactants that remain after reacting are called excess reagents. The out-of-date reactant is called a limiting reagent. After the barrier reagents are exhausted, no more reaction products are formed. Thus, the number of limiting reagents determines the amount of product produced.
Equation of reaction
Example of steps equalizing the reaction equation:
1. equalize the equation of the reaction
2. stoichiometric calculations
3. chemical calculations
4. equivalent results
Stoichiometry Reaction
In chemical reactions, the amount of reacting reactants is sometimes incompatible with the stoichiometric amount of the reaction (not in accordance with the coefficient ratio of the equivalent equation). Therefore, there will be reactants that have reacted first compared to other reactants. The reactants that remain after reacting are called excess reagents. The out-of-date reactant is called a limiting reagent. After the barrier reagents are exhausted, no more reaction products are formed. Thus, the number of limiting reagents determines the amount of product produced.
what are the benefits of stoichiometry in everyday life ?
BalasHapusThe benefits of stoichiometry in daily life
Hapus1 charging battery
2 symptoms of capillarity in water
3 kinetic theory of gas
4 calorimeters
5 heats / cooks
What every compound have empirical formula and molekuler formula?
BalasHapusAs has been alluded to the chemical formula is one of the characteristics of chemical compounds. The chemical formula of a compound represents the symbol and the number of elemental atoms composing a compound without reference to the compound including an ionic or covalent compound. The chemical formula itself is divided into empirical formulas and molecular formulas.
HapusThe molecular formula and the empirical formula of a compound differ only in the number of atoms, while the constituent elements of the compound remain. However, some compounds have the same molecular formulas and empirical formulas, for example H 2 O (water) and NH 3 (ammonia).
The number of atoms in a chemical formula expresses the number of moles of the related element, so the chemical formula of a compound is the mole ratio of the constituent element of the compound. From the atomic ratio or the ratio of this mole can be determined the ratio of mass and mass% of the elements that make up the compound.
To clarify this note the following example! Such as vitamin C containing ascorbic acid with C6H8O6 molecular formula, then:
· C6H8O6 molecular formula
· Comparison of moles of elemental atoms
C: H: O = 6: 8: 6
The amount of reactant reactant sometimes does not correspond to the number of stoichiometric reactions (not in accordance with the coefficient ratio of the equation equation). Explain the effect of the coefficient ratio in an equation
BalasHapusThe chemical equation shows the relationship between the number of moles of reactants and products in chemical reactions. For example, an equation representing combustion of butane gas.
Hapus2 C4H10 (g) + 13 O2 (g) → 8 CO2 (g) + 10 H2O (g)
Indicates that for every two moles of C4H10 reacting, thirteen required O2 moles and eight moles of CO2 and ten moles of H2O are produced. The relationship between the coefficients in the equilibrium equation of the number of moles of one substance to be reacted with, or generated from, a second substance can be calculated.
Example 3.2
If 3.5 mole of butane is burned in oxygen, calculate:
1. The number of moles of oxygen gas that would be required to react completely with it,
2. The mole amount of carbon dioxide is produced, and
3. The number of moles of water produced.
Answer
2 C4H10 (g) + 13O2 (g) → 8CO2 (g) + 10 H2O (g)
2 mol + 13 mol → 8 mol 10 mol
1.13 mol of O2 reacts with 2 moles of C4H10
N (O2) = 3/2 x n (C4H10) = 13/2 x 4.5 = 29 mol of O2
2. 8 moles of CO2 produced from 2 moles of C4H10
N (CO2) = 8/2 x n (C4H10) = 4 x 4.5 = 18 mol of O2
3. 10 moles of H2O is produced from 2 moles of C4H10
N (H2O) = 10/2 x n (C4H10) = 5 x 4.5 = 22 moles of O2
What is difference between of chemical formulas and chemical equations?
BalasHapusChemical Formulas As mentioned above is one of the hallmarks of chemistry. The chemical formula of a compound and the number of atoms containing the ionic or covalent compounds. The chemical formula itself is divided into empirical formulas and molecular formulas. Reaction equations
HapusAs mentioned in the previous chapter, the chemical changes that occur in matter are also called chemical reactions. Chemical reactions that occur can take place exotherm and endotherm. The reaction takes place exothermically when the reaction occurs with the release of some energy, whereas the opposite of the exothermic reaction is called the endothermic reaction. The energy involved can be light energy, heat energy and other energies.
In chemical reactions there are unchanged starting substances called reactants or reagents and substances that have undergone a change called a product or a reaction product. Substances involved in chemical reactions may be elements and compounds. The rectification here is not a fission or fusion reaction, so that the substances before and after the reactions are the same substances.
Chemical reactions that occur usually write in the form of reaction equations. The equation of a reaction is a statement expressing or describing a chemical process using a chemical formula. Therefore, the writing of the reaction equation must be able to express the actual chemical phenomenon, in which the reacting substances and the reaction products must be clearly described. To be more clear note the reaction that occurs between hydrogen gas and oxygen gas to form water,
Can you give me an example of stoichiometry other than in chemistry?
BalasHapusOn this page, you will learn about stoichiometric material. Seen from its definition, stoichiometry is a chemical branch associated with the existing quantitative relationship between reactants and products that occur in chemical reactions.
HapusWhen you enter the stoichiometric chapter, it means you will be more active to research about the chemical reactions and products it produces. Why study chemistry stoichiometry? In fact, this calculation is widely used as a basis in the calculations performed in the study.
For that, you can not underestimate this stoichiometric material. In addition, in this material, you will begin to actively perform calculations in chemistry lessons. Some of the materials to be discussed in stoichiometry include nomenclature of compounds, reaction equations, basic laws, stoichiometry of compounds, and stoichiometry of reactions.
What's the use of molarity?
BalasHapusMolarity is a quantity used to express the concentration or concentration of a solution. In this case, the molarity of a solution expresses the number of moles of dissolved substances in each liter of the solution. Mathematically, the molarity of a solution can be expressed as follows. M = n / v
HapusWhat units can be used in stoichiometry ?
BalasHapusMol and Avogadro numbers
HapusOne mole is the number of particles relative to 12 g of carbon-12. This number is called the Avogadro number of 6.022 × 1023 mol-1. Mol is an SI unit for the amount of substances and is widely used in chemical equations and calculations.
why it can be occure The comparison of the reaction coefficients can be interpreted as the mole ratio of the substances in the reaction?
BalasHapusThe reaction coefficient is the ratio of the number of particles of the substance involved in the reaction. Since 1 mole of each substance contains the same number of particles, the ratio of the number of particles is equal to the ratio of the number of moles. Thus, the reaction coefficient is the ratio of the number of moles of substances involved in the reaction and the ratio of the volumes of the gases in the reaction.
HapusIn general, to determine the coefficients in the chemical equations required a series of experimental results. One simple way to determine the reaction coefficient is by the method of continuous variation. Basically in a series of experiments carried out, the total molar amount of the reagent mixture is fixed while the molar amounts each are changed regularly (diversified regularly and continuously). Changes that occur due to a reaction between the mixture of the mixture such as mass, volume, and temperature are channeled to the molar amount of each reactant in a graph, to obtain an optimum point. The optimum point is formed expressing the coefficient ratio of each reagent (Keenan, 1992).