RENDEMEN
1. Rendemen
chemical
In chemistry, the chemical yield, the yield of the
reaction, or only the rendement refers to the amount of reaction product
produced in the chemical reaction. Absolute rendement can be written as weight in grams or in moles
(molar yield). The relative yield used as a calculation of the
effectiveness of the procedure is calculated by dividing the amount of product
obtained in moles by the theoretical yield in moles:
|
Fractional yield
= true
rendement
theoretical rendement |
To obtain a percentage yield, multiply the fractional
yield by 100%. One or more reactants in
chemical reactions are often used redundantly. The theoretical rendement
is calculated based on the number of moles of the limiting reaction. For
this calculation, it is usually assumed there is only one reaction involved.
The ideal chemical yield value (theoretical rendement) is
100%, a value highly unlikely to be achieved in its practice. Calculate the percentage of rendement that is by
using the following equation percent rendemen = weight yield / weight of yield
divided by the sample weight multiplied 100%.
2. Various
kinds of chemical reactions
By knowing some properties or types of reactions, we can
understand the chemical reactions more easily. Generally, chemical reactions are classified by
type as follows:
1. Reaction of merging
2. Decomposition reaction
3. Reaction of change (single exchange reaction)
4. Metathesis reaction (multiple exchange reaction)
1) Reaction
of merging
The merging reaction is a reaction in which two
substances merge to form a third substance. The simplest case is when two elements react to form a compound. For
example sodium metal reacts with chlorine gas to form sodium chloride. The
equation of the reaction:
2Na (s) + Cl2
(g) → 2NaCl (s)
Other examples are the reaction between white phosphor
and chlorine gas. In limited chlorine
amounts, phosphorus reacts to form phosphorus trichloride, PCl3, a
colorless liquid.
P4 (s) + 6Cl2
(g) → 4PCl3 (l)
If the chlorine is excessively available, the resulting
phosphorus compound is phosphorus pentachloride, PCl5, a white solid.
P4 (s) + 10Cl2
(g) → 4PCl5 (s)
Other merging reactions involve the compound as reagents. For example: phosphorus trichloride reacts with
chlorine gas to form phosphorus pentachloride. The equation of the
reaction:
PCl3 (l) + Cl2
(g) → PCl5 (s)
2) Decomposition
Reactions
The decomposition reaction is a reaction when a single
compound reacts to form two or more substances. Usually this reaction requires a rise in
temperature for the decomposable compound by increasing the temperature eg
KClO3. This compound when heated will decompose into KCl and oxygen gas. The
equation of the reaction:
KClO3 (s) → 2KCl
(s) + 3O2 (g)
Decomposition of potassium chlorate is commonly used to
generate laboratory oxygen gas. The decomposition reaction is commonly applied in limestone
processing in the area of West Java cipatat. Limestone, CaCO3 extracts
that can be used as building materials need to be further processed into tohor,
CaO. The processing of limestone is done by way of roasting limestone in
the stove. The chemical equations are:
CaCO3 (s) → CaO
(s) + CO2 (g)
In this reaction, a single compound is broken down into
two different substances.
3) Exhcange
Reactions
Reaction of a change or also called a single exchange
reaction is the reaction in which an element reacts with a compound to replace
the element contained in the compound. For example, if the copper metal plate is immersed in a silver
nitrate solution, a silver metal crystalline is produced. The equation of
the reaction is:
Cu (s) + 2AgNO3 (aq) → 2Ag (s) + Cu(NO3)2
(aq)
Copper replaces the silver contained in silver nitrate,
producing a solution of copper nitrate and silver metal.
If the logamseng plate
is immersed in a blue sulfate copper solution, then on the surface of the zinc
metal there will be a red copper deposit, and the blue color of the solution
slowly fades. This shows that zinc reacts with copper sulfate to produce
copper metal and a colorless zinc sulfate solution.
4) Metathesis
reaction
The reaction of metathesis or multiple exchange reactions
is a reaction involving the exchange of parts of the reactants. If the reagents are ionic compounds in solution
form, the exchange portion is the cation and anion of the compound. For
example a colorless potassium iodide solution is mixed with lead (II) nitrate
solution which is also colorless. The ions in the solution react to form a
yellow precipitate of the lead (II) iodide compound. The equation of the
reaction:
2KI (aq) + Pb (NO3)2 (aq) → 2KNO3
(aq) + PbI2 (s)
Iodide ions in the potassium iodide solution exchange
with nitrate ions from lead (II) nitrate solution, yield a colorless potassium
nitrate solution and a yellow i (y) iodide lead solid, as PbI2.
The acid and base reaction that produces salt, is also
considered a metathesis reaction. For example the reaction between hydrochloric acid, HCl (aq) and
sodium hydroxide (aq), the equation of the reaction:
HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)
The acid-base reaction is also called the neutralization
reaction, because it occurs the inclusion of the H + charge by the electrically
neutral (H2O) water-formed OH. The salt of NaCl formed remains in solution as its ions.
5) Burning
reaction
The reactions we consider so far can be characterized as
reactor reactions of atoms. However, we need to add another kind of reaction that is the
combustion reaction, which is characterized by the fact that one of its
reactants is oxygen. The combustion reaction is the reaction of a
substance with oxygen, usually reacting rapidly with the release of heat
forming a flame.
If carbon compounds are burned in oxygen or air will form
carbon dioxide and water vapor when the combustion is complete. However, if incomplete combustion (lack of
oxygen) will form carbon monoxide gas, or may be formed carbon black (soot). Some
examples of combustion of carbon compounds :
CH4 (g) + 2O2
(g) → CO2 (g) + 2H2O (g)
2CH3OH (l) +
3O2 (g) → 2CO2 (g) + 4H2O (g)
C4H10
(g) + 13O2 (g) → 8CO2 (g) + 10H2O (g)
Ironing, although not commonly considered as combustion,
is essentially a combustion reaction, because there is a reaction between iron
and oxygen accompanied by the release of energy. The iron-cellification
reactions are in fact very complex involving water molecules, but we can write
the karate in the form of a net reaction, which is as follows:
4Fe (s) + 3O2 (g) + nH2O (l) → 2Fe2O3.nH2O
(s)
3. Limiting
Reactions
In a chemical reaction, the mole ratio of the added
reagents is not always the same as the ratio of the reaction coefficient. This causes a reagent to be reacted first. This
is called pereaksi pembatas. Limiting reagent is a reactant contained in
the relatively smallest amount (in the stoichiometric relationship). The
limiting reagents will run out, while the other reactions will leave the rest.
4. Determining
the Limiting Reagent
Example:
One mole of sodium hydroxide solution (NaOH) is reacted with
1 mole of sulfuric acid (H2SO4) solution according to the
reaction
2 NaOH (aq) + H2SO4
(aq) -> Na2SO4 (aq) + 2 H2O (l)
Resolution:
Mol each substance is divided coefficient, then select
the small divide as a limiting reagent
- mole NaOH / NaOH coefficient
= 1/2 mol
= 0.5 mol
-
Mole H2SO4 / H2SO4
coefficient
= 1/1 mol
= 1 mol
Since the yield is NaOH < H2SO4, the NaOH
is the limiting reagent, so NaOH will be reacted first.
2 NaOH (aq) + H2SO4 > Na2SO4 (aq) + 2 H2O
(l)
First: 1 mol 1 mol 0 0
Reacts: (2x0.5) = 1 mol
(1x0.5) = 0.5 mol
Residual: 1-1 = 0 moles
1-0,5 = 0.5 mole 0.5 mole 1 mole
The remaining reagent is
H2SO4
Source
:
Sunarya,Y.(2003). Kimia
Dasar 2. Alkemi Grafisindo Press
Please explain to me more about how Determining the Limiting Reagent!
BalasHapusHi Agung, Thanks for the question. There are two ways to find the limiting reagent. The first way is to find the ratio of reactants used in the reaction (mole ratio). The second way to calculate the number of grams of the reaction.
HapusFirst way
Balance the reaction (note the coefficient in the chemical reaction)
Convert all the reactants in moles (usually stay divided by the mass of the atom or molecule relative)
Compare the numbers of moles in comparison with 2 reaction coefficient in number 1. My friend will be able to determine where the reactant is exhausted first.
Both Ways
Balance the reaction (note the coefficient in the chemical reaction)
Determine the number of moles of each reactant
Adjust to the reaction mole ratio coefficient then multiply by relative molecular mass
The resulting reaction gram at least that's the limiting reagent.
BalasHapusExplain the factors that affect the rendement results?
Hi Nida, thanks for the question.Factors that appear include:
Hapus1. Concentrations of reagents
Concentration has a very important role in the rate of reaction, because the greater the concentration of reagents, the collisions that occur more and more, thus causing the reaction rate faster. Likewise, if the smaller the concentration of reagents, the smaller the collision occurs between the particles, so the reaction rate becomes smaller.
2. Temperature
Temperature also plays a role in influencing the reaction rate. When the temperature at a reaction is increased, it causes the particles to move more actively, so that the collision happens more frequently, causing the reaction rate to increase. Conversely, when the temperature is lowered, the particles become less active, so the reaction rate gets smaller.
3. Pressure
Many reactions involve reactants in the form of gas. The speed of such reagents is also affected by pressure. The addition of pressure by minimizing the volume will increase the concentration, thereby enlarge the reaction rate.
4. Catalyst
A catalyst is a substance which accelerates the rate of a chemical reaction at a certain temperature, without undergoing change or being used by the reaction itself. A catalyst plays a role in the reaction but not as a reactant or product. The catalyst allows the reaction to take place more rapidly or allow the reaction to lower temperatures due to the changes triggered by the reagent. The catalyst provides an optional route with a lower activation energy. Catalyst reduced energy needed for reaction.
5. Touch Surface Area
Touch surface area has a very important role in the reaction rate, because the greater the surface area of touch between the particles, the collision is happening more and more, causing the reaction rate faster. Likewise, if the smaller the touch surface area, the smaller the collision occurs between the particles, the smaller the reaction rate. The characteristics of the reacted strips are also influential, ie the smoother the pieces, the faster the time it takes to react; While the more rough the pieces are, the longer the time it takes to react.
what the meaning of Limiting Reagent?
BalasHapusHi Nisa, Thanks for the question.The barrier reagent is a reactant substance discharged in a chemical reaction. The existence of a limiting reagent, means there are other reagents excess (remaining). The amount of reagent pereaksi determines how much the amount of the reaction product, so in calculating the chemical reaction, we must first determine the limiting reagents in the reaction.
HapusBased on the example of "Determining the Limiting Reagent", what is the volume when the STP state?
BalasHapusHi novi, thank you question. The volume of each reaction in the STP state is:
Hapus1. NaOH = 22.4 Liter
2. H2SO4 = 11.2 Liter
3. Na2SO4 = 11.2 Liter
4. H2O = 22.4 Liter
give an example of Limiting Reactants.
BalasHapusHi Intan, thanks for the question. Examples for limiting reactions are as follows and the discussion:
HapusAt the combustion of 2 moles of propane (C3H8) with 7 moles of oxygen gas produces carbon dioxide and water vapor.
Determine the number of moles of reactants remaining.
Determine the number of moles of carbon dioxide and water vapor produced.
Discussion
First determine the reaction equation:
C3H8 + 5O2 ---> 3CO2 + 4H2O
Determine the limiting reagent
C3H8 --- mol / reactant coefficient = 2/1 = 2
O2 --- mol / reactant coefficient = 7/5 = 1.4
The smallest is O2 so as a limiting reagent.
The number of moles of remaining reagents (C3H8) = 2 - 1.4 = 0.6 mol.
Determine the number of moles of CO2 and H2O
Mol CO2 = (CO2 coefficient / coefficient O2) x mole O2
Mol CO2 = (3/5) x 2 mol = 1.2 mol
Mol H2O = (coefficient H2O / coefficient O2) x mole O2
Mol H2O = (4/5) x 2 mol = 1.6 mol
What is the difference between reactions of merging and metathesis reaction? Please give me an example.
BalasHapusThe merging reaction is the two elements that react to form a compound whereas a metathesis reaction or a double exchange reaction is a reaction involving the exchange of parts of the reactant. If the reagents are ionic compounds in solution form, the exchange portion is the cation and anion of the compound
HapusExample of a merge reaction:
KClO3 (s) → 2KCl (s) + 3O2 (g)
And an example of a mathematical reaction:
2KI (aq) + Pb (NO3) 2 (aq) → 2KNO3 (aq) + PbI2 (s)
What are the factors that affect the decomposition reaction?
BalasHapusThe factors that influence the decomposition reaction are; Energy, catalysts, and elements that can form one more complex compound.
Hapusgive me an example the decomposition reaction?
BalasHapusthe example is :KClO3 (s) → 2KCl (s) + 3O2 (g)
HapusCaCO3 (s) → CaO (s) + CO2 (g)
wheter all element can experience a decompotion reactan ?
BalasHapusI think all are not all elements because only the elements or compounds are relatively simple and can combine to produce a more complex one that can undergo a decomposition reaction.
HapusIs there any application of remdemen in the health field?
BalasHapus