The term stoichiometry is derived from the Greek meaning stoicheon element and metron meaning measure. Thus, the stoichiometry is the study of the quantitative relationship between reactants and products in the reaction. Stoichiometry can also be said as a matter of chemistry.
In general, a chemical reaction takes place in solution. Before
you reacting solution, of course you would calculate in advance how
many agents will be treated and how much substance to be produced. In the chemistry that is studied in solution stoichiometry.To
understand the concept of stoichiometry of the solution, it must first
understand the types of reactions in an electrolyte solution, the sense
of concentration, mole concept, and the equation.A. Reactions in Solution ElectrolytesDo you still remember about a solution that can conduct electric current? Called the solution is the solution? The reaction taking place in the solution is the ionization reaction. The solution is an electrolyte solution. Electrolyte solutions are classified into two kinds of weak electrolyte solutions and strong electrolyte solutions.The
reaction between the ions in the electrolyte solution can generate
covalent compounds, sludge, gas, or discoloration of the solution.1. Acid base neutralization reactionThe reaction between acid and alkaline compounds can produce mineral salts and water
acid + bases ↔ salts + water
Example:KOH (aq) + HCl (aq) KCl (aq) + H2O (1)Mg (OH) 2 (aq) + H2SO4 (aq) MgSO4 + 2 H2O (1)The reaction between acids and bases commonly called neutralization reaction. However, not all salt produced from this reaction is neutral. There are salts that have acidic or alkaline properties. This depends on a strong or weak acids and bases react to form it.Strong acid + strong base → salt neutralStrong acid + base → salt weakly acidicweak acid + strong base → salt is alkalineThe concentration of acid or base solution can be determined based on the reactions that occur in the solution. This method is known as the acid-base titration. Titration
experiments performed by adding acid or base solution of known
concentration (a standard solution) to a solution of acid or base to
known concentration. The addition continued until the equivalent point is reached, the point at which acids and bases react right out. If
the volume of the standard solution and the sample solution is known,
the concentration of the sample solution can be determined.
2. Oxide Reaction with Acid TongueAlkaline oxides react with acids to form salts and waterOxides of acid + base → salt + H2OExample:K2O (s) + H2SO4 (aq) → K2SO4 (aq) + H2O (1)3. Acid Oxide Reaction with BasesThe reaction between oxides asama with bases to form salts and waterOxide acid + base → salt + H2OExample
4. Precipitation ReactionSome of cations and anions in the electrolyte solution to form a solution of poorly soluble in waterExample:
5. Reactions that Produce GasReaction abebrapa acid solution with metal to produce hydrogen gas.Metal oxide + acid → salt + H2Example:
Metal can react with acidic metal on the left side of hydrogen atoms on the following voltaic series:
B. Stoichiometric solutionMost chemical reactions can take place more quickly if the reactants in solution form. Why is that? What distinguishes the chemical reactions in solution (homogeneous mixture) with a heterogeneous mixture? Before discussion of the stoichiometric solution then we will discuss first about the concentration of the solution.
1. Concentrationa. Definition of ConcentrationConcentration is a general term to indicate the number of parts of the solute and solvent present in the solution. Concentration can be expressed quantitatively as well as qualitatively. For
a qualitative measure, the concentration of the solution expressed in
terms of a concentrated solution (concentrated) and liquid (dilute). The term second states the relative solute and solvent in the solution. Concentrated
solution means that a relatively large amount of solute, while the mean
number of aqueous solutes are relatively few. Typically, the terms concentrated and dilute concentrations used to compare two or more solutions.In a quantitative measure, the concentration of the solution expressed in g / mL (the same as the units for density). However, the stoichiometry calculations grams replaced with units of moles to obtain units of mol / L. Concentration in mol / L or mmol / mL known as molarity or molar concentration.b. MolarityMolarity
or kernolaran stating the number of moles of solute (n) in one liter of
solution (L) or millimoles of solute (n) in any one milliliter of
solution (mL).
Description: W = weight of substance (g)Mr = period of relative molecular substancesV = volume of solution (mL)A
solution can be prepared by dissolving the solute from the dilute
solution murniatau pekatnya: To be more clear, consider the following
example:1) Determination of Molarity by Dilution MethodIf
we want to make a 250 mL solution of 0.25 M K2CrO4 from the crystalline
form, the way is to calculate the mass of the substance to be
dissolved.mol K2CrO4 = 250 mL x 0.25 M= 0.0625 molg K2CrO4 = 0.0625 mol x 194 g / mol= 12.125 gSo, the thing to do is dissolve 12.125 g K2CrO4 crystals into 250 mL of water2) Determination of Molarity by Dilution MethodIf the solution above will be converted into 0.01 M K2CrO4 concentration, the way is by way of dilution. In dilution we will change the volume and kemolaran solution, but does not change the number of moles of solute.
nl = n2 → n = MV↓M1 V1 = M2V2Description:M1 = concentration before dilutionV1 = volume before dilutionM2 = concentration after dilutionV2 = volume after dilutionFor the above example, we can take 10 mL of 0.25 M K2CrO4 After that, the dilution calculation:M1V1 = M2V20.25 M x 10ml = 0.01 MxV2
= 250 mLSo, the thing to do is dilute 10 mL of 0.25 M K2CrO4 up the volume to 250 mL.If the two types of solutions are mixed and the number of moles of solute change (n1 does not equal n2), then the moles of the substance after mixed depending on the numbernl and n2, while the volume of the solution to V1 + V2.
2. Chemical Calculationsa. Mol and Reaction EquationsIn class X you have learned about the concept of the mole. On this subject, you will learn the concept of the mole and an integrated equation. We have discovered that one mole of a substance contains 6.02 x 1023 particles of the compound. If applied to an atom or molecule, then:1 mole = 6.02 x 1023 atoms / moleculesTo
remind the relationship between the concept of moles by the number of
particles, the mass of the atom / molecule, the standard volume and
molarity, note the diagram "Mol Bridge" below!
The chart above shows that the mole ¬ able to bridge the various parameters that allow us to understand a chemical reaction.On
the chart, it was shown that all paths leading to the mole using a
"division", while the path out of the mole using the "multiplication",
except for the molarity (M).For example, consider the following reaction?H2 (g) + O2 (g) - H2O (g)The
reaction shows that the number of oxygen atoms in the reactants are two
pieces, while the amount of oxygen in the product there is a fruit. This is different from the H atom is the same. Therefore, the reaction must be synchronized.Equalization of the reaction can be done by making the coefficient of O2 = ½ so that by the following equation.H2 (g) + ½ O2 (g) - H2O (g)In
the above reaction the number of atoms on the reactant O to H is
equivalent to the number of atoms of O and H on the product. Fractional number in the equation can be removed by multiplying two coefficients of all reactions.2H2 (g) + O2 (g) 2H2O (g)The above equation shows that the reaction coefficient respectively for H2, 02, and H2O is 2, 1, and 2. In
the calculation of chemical reaction coefficient represents the ratio
of moles of the substance in the reactants and products of a reaction. That is, the mole ratio in the reaction above, between H2, 02, and H2O is 2: 1: 2.Consider the illustration below!
2H2 (g) + O2 (g) ---------------- 2H2O (g)
2H2 (g) + O2 (g) ---------------- 2H2O (g)
Mole ratio of 2: 1: 2
Another example is the combustion of methane gas in the air.------------------------ methane + oxygen carbon dioxide + waterCH4 + 202 ---------- ------------- CO2 + 2H20
Equation shows that 1 mole of CH4 reacts with 2 moles of O2 to produce 1 mole of CO2 and 2 moles of H2O.From the equation we can say that:The number of moles of H2O produced = 2The number of moles of CH4 in action 1This comparison can be used to calculate the mass of water produced when burning a certain amount of methane in the air.b. Reaction Mass Calculation AgentIf
you want to do a reaction in the laboratory, you would measure the
reagents in units of grams or liters before rnereaksikannya. Therefore, work in the laboratory will always be associated with the mass calculation.Determination of the number of products and reactants involved in the reaction must be calculated in units of mol. That is, the unit-¬ units known to be changed into the form of a mole. The method is often used in chemical calculations is called the method of approach mol.Step-by-step method mole approach can be seen in the following steps.1. Give the equation of the matter in question, and then synchronized.2. Change all the known units of each substance into moles3. Use coefficients to balance the number of moles of reaction reactant substances and products.4. Change units of moles of substance in question into the unit in question.
C. Neutralization Reaction1. Titration ProcessOne application is the solution stoichiometry calculations find molarity or concentration of a substance in the sample solution through a process called volumetric analysis. Volumetric analysis is a quantitative chemical analysis is done by measuring the volume of a standard solution appropriate to react (react perfectly) with the solution being analyzed. For example, to search for the solution molarity Z, then Z is added to a solution of the standard solution resulting in complete reaction between the solution Z with standar.Larutan standard solution is a solution of the concentration or molarity standard pasti.Larutan have known there are 2 kinds, namely primary standard solution and secondary standard solution. Primary standard solution is a solution of the following standards are made, can be directly used to add to the concentration of the solution to be sought. Secondary standard solution standard solution after it is created can not be directly used, but must be checked again molarity concentration or by adding a solution of a primary standard. The process of checking the secondary standard solution with a solution of a primary standard is called standardization.The process of adding a standard solution to a solution of Z (which will be determined concentration) is called titration. This made the process of adding little by little (drop by drop) using an instrument called burette. Every single drop of standard solution out of the burette volume ± 20 mL. Substance to be titrated is placed in erlenmeyer.At the completion of the reaction between a standard solution with a solution called endpoint analyzed. At this point reached, the titration is stopped.In volumetric analysis, the reaction between the standard solution with the solution being analyzed must meet several requirements, among others:1. Chemical reactions that occur should be simple and straightforward equation written.2. Reactions should be able to run fast. Last drop of standard solution must be able to demonstrate complete reaction. If not, there will be mistakes titration.3. At the completion of the reaction (endpoint) is reached, there must of change in physical or chemical properties that can be observed or indication of changes can be detected by adding a solution of the indicator into the solution to be titrated or can be caused by the color of the solution own standards.For example, the neutralization reaction of NaOH solution with HC1 solution. Neither solution of NaOH or HC1 is the clear solution. The results of the reaction (NaCl and H20), is also the clear, so the endpoint can not be observed. To that end, in the titrated solution (NaOH), was added a solution of indicators, such as phenolphthalein indicator, abbreviated (pp) is an indicator that in alkaline solution gives red color in acidic solution is colorless. The addition of these indicators using a Pasteur pipette. The number of indicator solution were added just one or two drops. Titration of NaOH with HC1 using pp indicators and endpoint is reached when the last drop addition of HCl solution gives discoloration.
2. Titration Acids BasesOne application of the concept of neutralization reaction is the acid-base titration. In acid-base titration, the value of the equilibrium constant of ionization used as a benchmark for determining the pH of the solution while achieving equivalent point. Equivalent point or end point is when the theoretical amount of acid or base added exactly equivalent stoichiometric with the amount of base or acid in the solution • analyzed.The formula can be used to determine the concentration of the sample solution is as follows:Sample mol = standard mol M sample V sample = M standard Vstandard
C. Neutralization Reaction1. Titration ProcessOne application is the solution stoichiometry calculations find molarity or concentration of a substance in the sample solution through a process called volumetric analysis. Volumetric analysis is a quantitative chemical analysis is done by measuring the volume of a standard solution appropriate to react (react perfectly) with the solution being analyzed. For example, to search for the solution molarity Z, then Z is added to a solution of the standard solution resulting in complete reaction between the solution Z with standar.Larutan standard solution is a solution of the concentration or molarity standard pasti.Larutan have known there are 2 kinds, namely primary standard solution and secondary standard solution. Primary standard solution is a solution of the following standards are made, can be directly used to add to the concentration of the solution to be sought. Secondary standard solution standard solution after it is created can not be directly used, but must be checked again molarity concentration or by adding a solution of a primary standard. The process of checking the secondary standard solution with a solution of a primary standard is called standardization.The process of adding a standard solution to a solution of Z (which will be determined concentration) is called titration. This made the process of adding little by little (drop by drop) using an instrument called burette. Every single drop of standard solution out of the burette volume ± 20 mL. Substance to be titrated is placed in erlenmeyer.At the completion of the reaction between a standard solution with a solution called endpoint analyzed. At this point reached, the titration is stopped.In volumetric analysis, the reaction between the standard solution with the solution being analyzed must meet several requirements, among others:1. Chemical reactions that occur should be simple and straightforward equation written.2. Reactions should be able to run fast. Last drop of standard solution must be able to demonstrate complete reaction. If not, there will be mistakes titration.3. At the completion of the reaction (endpoint) is reached, there must of change in physical or chemical properties that can be observed or indication of changes can be detected by adding a solution of the indicator into the solution to be titrated or can be caused by the color of the solution own standards.For example, the neutralization reaction of NaOH solution with HC1 solution. Neither solution of NaOH or HC1 is the clear solution. The results of the reaction (NaCl and H20), is also the clear, so the endpoint can not be observed. To that end, in the titrated solution (NaOH), was added a solution of indicators, such as phenolphthalein indicator, abbreviated (pp) is an indicator that in alkaline solution gives red color in acidic solution is colorless. The addition of these indicators using a Pasteur pipette. The number of indicator solution were added just one or two drops. Titration of NaOH with HC1 using pp indicators and endpoint is reached when the last drop addition of HCl solution gives discoloration.
2. Titration Acids BasesOne application of the concept of neutralization reaction is the acid-base titration. In acid-base titration, the value of the equilibrium constant of ionization used as a benchmark for determining the pH of the solution while achieving equivalent point. Equivalent point or end point is when the theoretical amount of acid or base added exactly equivalent stoichiometric with the amount of base or acid in the solution • analyzed.The formula can be used to determine the concentration of the sample solution is as follows:Sample mol = standard mol M sample V sample = M standard Vstandard
why the reactions between the ions in the electrolyte solution can produce covalent compounds, sediments, gas, or discoloration of the solution?
BalasHapusok rini, i'll try to answer ur guestion.
BalasHapusthe reaction between the ions in the electrolyte solution can produce covalent compounds,sediments,gas,or discoloration of the solution because the solutions react with each other. the reaction can be on the mark with the these things.