A.
ENERGY OF
ACTIVATION
Why
are some chemical reactions going through lightning fast while others take
days, months and even years to produce enough products? How can a catalyst
increase the rate of a chemical reaction? Why do small temperature changes
often have a big effect on cooking rate? How does the study of the rate of
chemical reactions provide information about how molecules combine to form
products? All of these questions concern chemical kinetics as yet incomplete as
thermodynamics. There are still many reactions whose equilibrium constants are
well-known, but the details of the reaction path are still not understood. This
is especially true for reactions involving many of the reactant elements that
make up the product.
You
have previously known that the reaction rate is influenced by several factors
including, concentration, temperature, surface area and catalyst. What causes
this factor can affect the rate of the reaction. One of the famous theories to
explain it is known as "The Collision Theory". In this theory,
chemical reactions are the result of collisions between reacting particles.
However, not every collision between particles causes a reaction. In order for
the reaction, each particle must have a very large kinetic energy. Kinetic
energy is used to break old bonds to form new bonds.
The minimum kinetic energy required by the reactant substances particles (reactants) to react to form an activated complex is called activation energy (Ea). This activation energy was first proposed, Svante Arrhenius. The relationship between the activation energy and the reaction rate is described as the curve:
The relationship between the rate of
reaction and the course of a reaction can be analogous to the process of
pushing the car from one place to another through the ascending and descending
path. When the car is pushed up to the X mark, then the driver can no longer
afford it then the car goes down again. The car does not make it past the peak
and does not reach B. It is analogous to a collision event that has less
kinetic energy than Ea (not up to peak). In order for the car to arrive at B,
the car must be pushed minimum to the top so that the car can reach B without
being pushed. The amount of energy required to push the car to peak is
analogous to the energies of activation
RELATIONSHIP BETWEEN THEORETICAL THEORIES
AND FACTORS AFFECTING THE REACTION
To speed up the rate of reaction there are two
ways that can be done, namely enlarge the kinetic energy of molecules or lower
the price Ea. Both ways are intended to make more and more molecules have the
same or more energy of activation energy so that more and more collisions. This
activation energy can explain why the concentration, temperature, surface area
and catalyst can affect the rate of reaction
1. Temperature
In general, the reaction will take place more quickly when the temperature is raised. With Raising the temperature then the kinetic energy of the reacting molecules will Increases so that more molecules will have energy equal to or greater than Ea. Thus more molecules can reach the transition state or in other words the reaction rate becomes larger. Mathematically the relationship between the value of the reaction rate constant (k) to temperature is expressed by the formulation
2. Concentration
A substance that reacts has different concentrations. The concentration states the influence of concentration or substances that play a role in the reaction process. The greater the concentration, the faster the reaction rate. This is because a large concentration of substances contain more number of particles, so that the particles are denser more dense than the low concentration of the substance. Particles that are more tightly arranged, will often collide compared with the tenuous particles, so the possibility of reaction is getting bigger. (Utami, 2009)
3. Catalysis
catalysis is an event of increased reaction rate as a result of the addition of a catalyst. Although the catalyst decreases the activation energy, it does not affect the energy difference between the product and the reagents. In other words, the use of a catalyst will not alter the enthalpy of the reaction.
4.
Surface area
The larger the
surface area then the chances of colliding, the higher the collision, the
faster the reaction rate. Expanding the surface area here is the overall
surface area not per particles. Consider the following illustration:
Catalyst The catalyst is a substance that can speed up a reaction but does not
undergo a permanent chemical change, so that at the end of the reaction the
substance can be recovered. The catalyst accelerates the reaction by lowering
the activation energy (Ea) price.
What is the role of the catalyst in the reaction
BalasHapusAccelerate the reaction. The catalyst reacts but is separated in the reaction product
BalasHapuswhat is example catalysis ?
BalasHapusThe catalyst is a substance that accelerates the rate of reaction of a chemical reaction at a certain temperature, without undergoing change or being used by the reaction itself (see also catalysis). A catalyst plays a role in the reaction but not as a reactant or product.
BalasHapusThe 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.
The catalyst can be divided into two main groups: homogeneous catalyst and heterogeneous catalyst. Heterogeneous catalysts are catalysts present in different phases with reactants in their catalyzed reactions, while homogeneous catalysts are in the same phase. One simple example for heterogeneous catalysis is that the catalyst provides a surface in which reagents (or substrates) are temporarily absorbed. The bonds in the substrates are weakened in such a way that adequate new products are formed. Katan atara products and catalyst weaker, so finally released.
What should we do if the temperatures we test differ from those in the literature
BalasHapusOf course all we need to do is to first calibrate the thermometer we will use, then do the experiment in accordance with the working procedure, so that the results in accordance with the literature, so the probable problem is the thermometer or the procedure.
Hapuswhy the concentration, temperature, surface area and catalyst can affect the rate of reaction?
BalasHapusOf course the four things can affect the rate of reaction, the higher the concentration the faster the reaction, the greater the surface of the touch field then smakin rapid reaction, the higher the temperature will dampen the rate of reaction, and the catalyst as a decrease in activation energy so that the reaction will run faster.
Hapus