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.
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 the same as 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.The Law of Conservation of Mass
Mass Loss Law: The mass of the product is equal to the mass of the reactantsFixed Comparative Law (Proust Law)
Fixed Comparison Law: The chemical compound consists of chemical elements with the ratio of the mass of elements that remain the same.The Law of Multiple Comparisons (Dalton's Law)
The Law of Multiple Comparisons: If an element reacts with other elements, then the ratio of the weight of the element is a simple integer
So from persmaaan:
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:
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
The condition in which the equation of the reaction is equal is when it satisfies the following two criteria:The number of atoms of each element on the left and right sides of the equation has been the same.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.
In real life, this is an example:To make a delicious cup of coffee, a recipe is required that is 9 cube sugar with 3 tablespoons of coffee.
This is a fix and patent recipe. So what if we have 12 sugar cubes and three spoons of coffee powder, how many cups of coffee can be made?Yes! The answer is 1 cup of coffee, with the remaining ingredients 3 cube sugar.How about we have 27 sugar cube and 8 spoons of coffee. How many cups of coffee can be made?Of course 2 glasses of coffee with the remaining 9 sugar cube and 2 coffee spoons. All absolutely must follow the recipe.
The key is that all must follow the prescription, if in stoichiometry, the equivalent reaction equation is the recipe, so we must follow the recipe.
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 Mask 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 / molThe 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. If there is not yet understand about mole please go to wikipedia about mole understanding.
The formula of the interest of the mole of the compound is:
Mol = m / Mrwith;Mol -> mol CompoundsM -> Mass of Compound (gr)Mr -> Molar Mass (Reality Mass)Sample Problem Involving Chemical Stoichiometric Calculations
Propane burns by reaction equation:C3H8 + O2 → H2O + CO2
If 200 g of propane is burned, then what is the amount of H2O formed?Answer:
First: Resolve the equation of the reaction!C3H8 + 5O2 → 4H2O + 3 CO2Second: 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)
Fourth: Calculate the moles of H2O by comparisonMol 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.
What is law was put forward by John Dalton?
BalasHapusand what is the mole formula?
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HapusKey Points
Dalton's atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties.
Dalton based his theory on the law of conservation of mass and the law of constant composition.
The first part of his theory states that all matter is made of atoms, which are indivisible.
The second part of the theory says all atoms of a given element are identical in mass and properties.
The third part says compounds are combinations of two or more different types of atoms.
The fourth part of the theory states that a chemical reaction is a rearrangement of atoms.
Parts of the theory had to be modified based on the discovery of subatomic particles and isotopes.
HapusDalton's atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties.
Dalton based his theory on the law of conservation of mass and the law of constant composition.
The first part of his theory states that all matter is made of atoms, which are indivisible.
The second part of the theory says all atoms of a given element are identical in mass and properties.
The third part says compounds are combinations of two or more different types of atoms.
The fourth part of the theory states that a chemical reaction is a rearrangement of atoms.
Parts of the theory had to be modified based on the discovery of subatomic particles and isotopes.
Please explain about law avogadro!
BalasHapusAvogadro's Law (Avogadro's theory; Avogadro's hypothesis) is a principle stated in 1811 by the Italian chemist Amedeo Avogadro (1776-1856) that "equal volumes of gases at the same temperature and pressure contain the same number of molecules regardless of their chemical nature and physical properties". This number (Avogadro's number) is 6.022 X 1023. It is the number of molecules of any gas present in a volume of 22.41 L and is the same for the lightest gas (hydrogen) as for a heavy gas such as carbon dioxide or bromine.
HapusThe law can be stated mathematically
.
where:
V is the volume of the gas.
n is the amount of substance of the gas.
k is a proportionality constant.
The most important consequence of Avogadro's law is that the ideal gas constant has the same value for all gases. This means that the constant
where:
p is the pressure of the gas
T is the temperature of the gas
has the same value for all gases, independent of the size or mass of the gas molecules.
One mole of an ideal gas occupies 22.4 liters (dm³) at STP, and occupies 24.45 litres at SATP (Standard Ambient Temperature and Pressure = 273K and 1 atm or 101.325 kPa). This volume is often referred to as the molar volume of an ideal gas. Real gases may deviate from this value.
Or to put it another way "the principle that equal volumes of all gases at the same temperature and pressure contain the same number of molecules. Thus, the molar volume of all ideal gases at 0° C and a pressure of 1 atm. is 22.4 liters"
Avogadro's number is one of the fundamental constants of chemistry. It permits calculation of the amount of pure substance (mole), the basis of stoichiometric relationships. It also makes possible determination of how much heavier a simple molecule of one gas is than that of another, as a result the relative molecular weights of gases can be ascertained by comparing the weights of equal volumes.
Avogadro's number (conventionally represented by N' in chemical calculations) is now considered to be the number of atoms present in 12 grams of the carbon-12 isotope (one mole of carbon 12) and can be applied to any type of chemical entity.
'Make an example of a problem that involves chemical calculation with its solution?'
BalasHapusMany experiments involving chemicals call for their use in solution form. That is, two or more substances are mixed together in known quantities. This may involve weighing a precise amount of dry material or measuring a precise amount of liquid. Preparing solutions accurately will improve an experiment's safety and chances for success.
HapusCan you explain about stoichiometry is a subject in chemistry that studies the quantity of matter in a chemical reaction?
BalasHapusStoichiometry is a branch of chemistry that deals with the relative quantities of reactants and products that are consumed/produced within a given chemical reaction. In order to make any stoichiometric determinations, however, we must first look to a balanced
Hapuschemical equation. In a balanced chemical equation, we can easily determine the stoichiometric ratio between the number of moles of reactants and the number of moles of products, because this ratio will always be a positive integer ratio. Consider the reaction of nitrogen gas and hydrogen gas to form ammonia (NH3):
N2(g)+3H2(g)→2NH3(g)
From the balanced equation, we can see that the stoichiometric coefficient for nitrogen is 1, while for hydrogen it is 3, and for ammonia it is 2. Therefore, the stoichiometric ratio, oftentimes referred to simply as the "mole ratio" or "molar ratio," between N2(g), H2(g), and NH3(g) is 1:3:2. In the special case where reactants are combined in their molar ratios (in this case, 1 mole of N2(g) and 3 moles of H2(g)), they will react completely with each other, and no reactant will be left over after the reaction has run to completion. However, in most real-world situations, reactants will not combine in such perfect stoichiometric amounts. In most cases, one reactant will inevitably be the first to be completely consumed in the reaction, causing the reaction to come to a halt. This reactant is known as the limiting reactant, or limiting reagent.
From this brief description, we can see that stoichiometry has many important applications. As we will see, through balancing chemical equations and determining the stoichiometric coefficients, we will be able to determine the number of moles of product(s) that can be produced in a given reaction, as well as the number of moles of reactant(s) that will be consumed. Stoichiometry can also be used to make useful determinations about limiting reactants, and to calculate the amount of excess reactant(s) left over after a given reaction has run to completion.
Alkali metals (Group 1) react with halogens (Group 17) to form ionic compounds of metal halides. How many grams of potassium chloride formed from a reaction of 5.25 L of chlorine gas at a pressure of 0.950 atm and a temperature of 293 K with 17.0 g of potassium?
BalasHapus