QUESTIONS (CHEMICAL EQUATIONS AND HARDNESS OF WATER)

                                                   

                                            WEEKLY TEST

1)Define the following terms
              a)Spectator ions
              b)ionic equation
              c)redox reaction

2)Differentiate between ionic and molecular equations.

3)Using equations,explain the following types of reactions.
             a)precipitation reaction
             b)synthesis reaction
             c)displacement reaction
4)complete and balance the following
           a)Zn(NO₃)_{2(s) →
            b)}Cu_(s) + HNO_{3(aq)→
            c)}Na₂CO_3(aq) + Ca(HCO₃)_{2(aq)→
            d)}NH_3(g)  + Cl_2(g)→
5)Give two advantages and two disadvantages of  hard water.
6)explain how an  ion exchanger works in removing hardness of water.
7)explain four ways of removing permanent hard ness of water.
8)differentiate between hard water and soft water.
9)state the causes of permanent and temporary hardness of water.
10)give the meaning of the following
               a)soft water
               b)hard water
               c)permanent hard water

        

                                   

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TOPIC 2:HARDNESS OF WATER

                                          HARDNESS OF WATER

                                           

                                                 
                       WATER
            Is a colourless compound of hydrogen and oxygen elements chemically combined together.
water contains dissolved minerals this make water to become hard.
     
                                           TYPES OF WATER
There are two types of water depending on dissolved  minerals or compound,these are;

1. hard water
2. soft water              

                                      1:HARD WATER

Is the one that does not readily form lather with soap,due some dissolved substances such as Ca and Mg ions.
                                     2:SOFT WATER

Is the one which lathers readily with soap.or is water which has low concentration of calcium carbonate and other ions.

                                   CAUSES OF HARDNESS OF WATER
Water is said to be hard if it contain calcium and magnesium ions of their dissolved salts.these Calcium and magnesium salts are;
                     calcium sulphate(CaSO4)
                     Magnesium chloride(MgCl)
                     magnesium sulphate(MgSO4)
                   
                                    TYPES OF HARDNESS OF WATER
There are two types of hardness of water,which are;
             
             1:temporary hardness of water(temporary hard water)
             2.Permanent hardness of water(permanent hard water)


    1:TEMPORARY HARD WATER

Is the water that can be softened by boiling or adding lime .Temporary hard water contains hydrogencarbonates of calcium and magnesium.

      Ca(HCO3)2→H2O +CO2+CaCO3

    METHORDS  OF REMOVING TEMPORARY HARDNESS OF WATER

• By boiling               Ca(HCO3)2→CaCO3 + H2O + CO2

• Adding slaked lime(Ca(OH)2                   Ca(HCO3)2 + Ca(OH)2→ CaCO3 + H2O + CO2

• Adding washing soda (Na2CO3) 

       .distillation                                                                                                                                                                                                                                                                                                                                     2:PERMANENT HARD WATER

Is water that can not be soften by boiling.

             CAUSES OF PERMANENT HARDNESS OF WATER

Is caused by presence  of sulphate ions () and chlorides ions of calcium and magnesium.

       →these compounds of calcium and magnesium are:

                         magnesium suphate

                         magnesium chloride

                         calcium sulphate

                        calcium chloride

         METHORDS OF REMOVING PERMANENT HARD WATER

• Distillation
• by permutit process(ion exchange process)
• by adding washing soda
• using synthetic ions                                                                                                                                                                                                                                                                                                                     ADVANTAGES OF HARD WATER
• Has good taste due to dissolved minerals 
• helps for formation of bones and teeth eg;calcium
• helps in formation of strong shells of aquatic organisms
• Helps to prevent corrosion in water pipes
• hard water is generally safer for drink more than soft water
• hard water does not dissolve lead(Pb),as the result it does not cause lead poisoning when lead is used in transferring the water into households.                                                                                                                                                                                                                                                                                                                                                                                                                                     DISADVANTAGES OF HARD WATER
• It waste soap during washing clothes
• It wastes fuels in boilers
• it cause formation of scum on clothes and utensils
• It causes limescale in water boilers,kettles and water pipes
• wastes time during washing clothes
• elimika

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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 

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