TOPIC1:CHEMICAL EQUATIONS

    

                                CHEMICAL REACTIONS
                                           
                                     

 Is the process or event in which a chemical substances change into a different substance.
Chemical reactions happen when atoms and molecules rearrange themselves to form new compounds.

Reactants these are chemicals that begin the reaction. Products these are new substances formed after the reaction. Products have qualities that are  different from the original Reactants.
                     
                        The characteristics of chemical reactions are;
   a) One or more new chemical substances are formed
   b) Energy is given out or taken in during reactions
   c) A reaction may be reversible or irreversible

Reversible reaction this is the reaction that proceed in either directions (forward or backward ).In forward reaction Reactants are converted into products while in backward reaction the products are converted into original Reactants. The reaction is denoted by double half arrows
       
           Reactantsproducts

Irreversible reaction this is the reaction that proceed in only one direction.
It is denoted by full arrow
                       →
                                   
                                 CHEMICAL EQUATIONS

Chemical equation is the symbolic representation  of chemical reaction.
In chemical equation the Reactants are placed on the left_hand side of the equation and products are placed on the right hand side.
        eg.
                H2 + Cl2→HCl

H2 and Cl2  are Reactants and HCl is the product . reactants and products are separated by an arrow (→)
 Chemical equations may be written in words (word equation) or in symbolic form (formula equation)

during the reaction reactants can either be gases(g),liquid(l), solid(s) and sometimes substances dissolved in water are involved in reactions,the word aqueous(meaning the solution has been dissolved in water) is used and the symbol for it is (aq)
these symbols must be included in chemical equation

                                           WRITING AND BALANCING EQUATIONS

chemical equation must be written in accordance to law of conservation of matter.which states that "In chemical reaction,the total mass of the products equals the total mass of the reactants"
this means number of atom on both side of the equation should be equal to ensure the equation is balanced

                                        steps for writing and balancing chemical equations
    1)write the equation in word form.
example;
       zinc metal reacts with hydrochloric acid to produce zinc chloride and hydrogen gas

  2)write complete word equation using arrow to separate reactants from products
example;

              zinc  + hydrochloric acid→zinc chloride+hydrogen gas

  3)write the equation using correct symbols and formula.

  Zn + HCl→ZnCl2+H2

  4)Balance the number of atoms of all element on each side 

Zn + HCl  → ZnCl₂ +H₂ (Unbalanced)

Zn + 2HCl →ZnCl₂  + H₂ (Balanced)

   5)Introduce the state symbols of each chemical species in the equation 

Zn_(s) + 2HCl_(aq) ZnCl_2(aq) + H<sub>2(g)

                                EXERCISE</sub>

_{1;Write a balanced chemical equation for the reaction between dilute sulphuric acid with                 a)}BaCl_{2 solution                 b)}NaHCO_{3 powder                     c)}NaOH solution              d)ZnO powder

2;writing the following formula equation into word equation 

                    

                  a)Fe + Cl_2→ FeCl₃  

                     _b)CaCO_3→ CaO + O₂                     

                     _c)NaHSO₄ + CaCl NaCl + CaSO₄ + H₂

                    

                                        _{CHEMICAL REACTIONS}

Is an event in which a chemical substances change into different substances 
       

                                     TYPES OF CHEMICAL REACTION

   a)Combination reaction (synthesis reaction)

 b)Decomposition reaction 

  c)displamecent reaction