CHEMICAL REACTIONS

CHEMICAL REACTIONS

 

               A chemical reaction is a natural process that always results in inter-change of chemical compounds. Compound or compounds early in the reaction is referred to as the reactants. Chemical reactions are usually characterized by a chemical change, and will produce one or more products that typically have characteristics that are different from the reactants. Classically, chemical reactions involve changes involving the movement of electrons in the forming and breaking of chemical bonds, although the general concept is basically a chemical reaction can also be applied to the transformation of elementary particles such as the nuclear reaction.

                                          

                                    CHARACTERISTICS OF CHEMICAL REACTION
 
1. Colour Change Happen

In a chemical reaction, reactants are converted into products. Changes may occur due to the termination of the bonds of the reactants and the formation antaratom ties bru that make up the product. Energy required to break the tie. To form a new bond, released some energy. Thus, the chemical reaction energy changes.

Chemical reactions that produce energy in the form of heat is called exothermic reactions. Reactions that absorb heat energy called endothermic reactions.

Example: Fire can warm up a cold and when hot breath in the body due to exercise so that the body becomes cold expelled.

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2. Temperature changes occur

In a chemical reaction, reactants are converted into products. Changes may occur due to the termination of ties antaratom reagents and formation of new bonds that make up the product. Energy required to break the tie.

Chemical reactions that produce energy in the form of heat is called exothermic reaction, while the reaction absorbs heat energy called endothermic reactions.

A chemical reaction occurs in a space that we call dbngan system, places outside the system is called the surroundings.

In exothermic reactions, heat transfer occurs from sisitem to the environment.

In endothermic reactions occur transfer heat energy from the environment to the system.

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3. Sediment formation occurs

When two solutions react in a test tube, sometimes forming an insoluble sneyawa, solid, and separated from the solution. The solid is called the precipitate (precipitate)

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4. Gas Formation occurs

Simply put, the chemical reaction created a gas which indicated the presence of bubbles in solution reacted. The gas can be determined from the typical smell, like sour sulfide (H2S) and ammonia (NH3), which stinks.


                         TYPES OF CHEMICAL REACTIONS IN ELECTROLYTE SOLUTIONS
 
1. Neutralisation reaction
          a. Acid + base → ​​salt + water
              HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)
                  b. Bases Oxide + Acid → Salt + Water
              Na2O (aq)) + HCl (aq) → NaCl (aq) + H2O (l)
          c. Oxide Acid + base → ​​salt + water
              SO3 (g) + NaOH (aq) → Na2SO4 (aq) + H2O (l)
 
2. Reaction Formation Gas
          a. Active metals (except Cu, Hg, Ag, Pt, Au) + Strong Acid → Salt + H2 gas
               Mg (s) + HCl (aq) → MgCl2 (aq) + H2 (g)
                  b. Metals other than Pt, Au + Strong Acid → Salt + Water + Gas other
               Cu (s) + H2SO4 pk → CuSO4 (aq) + SO2 (g) + H2O (l)
                Cu (s) + HNO3 pk → Cu (NO3) 2 (aq) + NO2 (g) + H2O (l)
                Cu (s) + H2SO4 aqueous (aq) → CuSO4 (aq) + H2 (g)
                Cu (s) + dilute HNO3 (aq) → Cu (NO3) 2 (aq) + NO (g) + H2O (l)
          c. Salt + else + Acid → Salt Gas
                CaCO3 (s) + HCl (aq) → CaCl2 (aq) + CO2 (g) + H2O (l)
          d. Strong Bases ammonium salt → salt + else + Gas + Water
                NH4Cl (aq) + NaOH (aq) → NH3 (g) + H2O (l) + NaCl (aq)
3. Precipitation reaction
          a. Salt Salt 1 + 2 → 3 + Garam Garam 4
               Na2CO3 (aq) + CaCl2 (aq) → CaCO3 (s) + NaCl (aq)

                                                                      EQUATION

                    In chemistry, the chemical equation or equation is symbolic writing of a chemical reaction. Reagent chemical formula written on the left equations and chemical formulas written on the right product. Coefficients are written on the left of the chemical formula of a substance is the stoichiometric coefficient, which describes the amount of the substance involved in the reaction relative to other substances. Equation that was first created by a iatrokimia Jean Beguin in 1615.
In an equation, reactants and products are connected through different symbols. The symbol → is used for unidirectional reaction, ⇆ for the reaction in both directions, and ⇌ for the equilibrium reaction. For example, the equation for the combustion of methane (a gas to natural gas) by oxygen is written as follows
CH4 + 2 O2 → CO2 + 2 H2O
Often in an equation written form substances that react in the stands to the right of the chemical formulas of these substances. The letter s represents the solid, l represents the liquid, g represents the gas, and symbolizes aq solution in water. For example, the reaction of solid potassium (K) and water (2H2O) yields a solution of potassium hydroxide (KOH) and hydrogen gas (H2), is written as follows
2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)
In addition, on the far right of the equation sometimes there is a constant amount or, for example, the change in enthalpy or equilibrium constants. For example, the Haber process (ammonia synthesis reaction) with the change in enthalpy (ΔH) written as
N2 (g) + 3H2 (g) → 2NH3 (g) ΔH = -92.4 kJ / mol.
An equation is called equivalent if the amount of an element on the left side of the equation equal to the number of elements on the right, and the ionic reaction, the total charge must be equal as well.

                           FACTORS AFFECTING THE RATE OF CHEMICAL REACTION
Experience shows that the wood chips burn faster than wood blocks, this means that the rate of reaction can take place with the same yag different pace, depending on the state of reactants. This section will discuss the factors that affect the rate of reaction. Knowledge of this allows us to control the rate of reaction, which slows the adverse reactions and increase the rate of reaction favorable.
1. Reagent Concentration
Concentration has a very important role in the reaction rate, because the besarkonsentrasi reagent, it is happening more and more collisions, resulting in faster reaction rates. Likewise, if the smaller concentration of reactants, the smaller inter-particle collisions that occur, so that the reaction rate was smaller.
2. Temperature
Temperature also played a role in affecting the rate of reaction. If the temperature in a reaction that berlangusng raised, it causes the active particles move so collisions are more frequent, causing the reaction rate increases. Conversely, if the temperature is lowered, the particles grew more active, so the smaller the rate of the reaction.3. Pressure
Many reactions involving reactants in gaseous form. The rate of the reagent as it also affected the pressure. The addition of pressure to minimize the volume will increase concentration, and thus can increase the rate of reaction.4. Catalytic
A catalyst is a substance that accelerates the rate of a chemical reaction at a certain temperature, without changing or unused by the reaction itself. A catalyst role in the reaction but not as a reactant or product. The catalyst allows the reaction go faster or enable the reaction at lower temperatures due to the changes that triggered the reagent. Catalysts provide a pathway option with a lower activation energy. The catalyst reduces the energy required for the reaction.5. Surface TouchThe surface area of ​​the touch has a very important role in the reaction rate, because the larger the surface area of ​​the touch area between the particles, the collision happened more and more, resulting in faster reaction rates. Likewise, if the smaller surface area of ​​the touch, the smaller inter-particle collisions that occur, so that the reaction rate was smaller. The characteristics of the treated pieces were also influential, namely the more subtle pieces, then the less time it takes to react, while the coarse pieces, then the longer it takes to react.