VOLUMETRIC ANALYSIS

Standard Volumetric Apparatus
The Concept of Volumetric Analysis
Explain the concept of volumetric analysis
           

Volumetric analysis is a quantitative analysis involving the measurement of different solutions. These solutions are made to react completely and the completion of the reaction is indicated by certain substances called indicators. The quantitative composition of the solution is then determined.
Important steps of volumetric analysis include:
Weighing;
Preparation of the solution;
Titration; and
Calculation
In volumetric analysis, we deal with volumes of solutions. That is why this quantitative determination of solutions of substances is called volumetric analysis.
The amount of a substance present in a solution is given in terms of its volume and its concentration. The volume of a solution is usually given in litres (dm3). The concentration of a solution is given in moles per litre (mol/dm3) or grams per litre (g/dm3).
Volumetric analysis is a means of finding the concentration of an unknown solution. For example, the concentration of an unknown solution of an acid can be found if it is reacted with a standard solution of an alkali.
A standard solution is one whose concentration is well known and does not change with time.
In volumetric analysis, the reaction is carried out in a carefully controlled way. The volumes are measured accurately using a pipette and burette.
The method is to add a solution of one reactant to the solution of another reactant until the reaction is complete. When the reaction is complete, we say the end-point has been reached. If the reactants are acids and bases, completion (end-point) is determined by the change in colour of an acid-base indicator. The method is called titration. In other reactions, completion is determined by a colour change of reactant(s). The concentration of one of the reactant solutions must be known in order to be able to find the concentration of unknown solution.

Significance of Volumetric Analysis

Volumetric analysis is used to quantify the amount of substances present in solutions by analytical procedure, which involves precise measurements of volumes of solutions and masses of solids.
Volumetric analysis helps in the determination of the accurate volumes and concentrations of the reacting substances, often solutions.
Volumetric analysis (titration) helps in the preparations of standard solutions.
Volumetric analysis knowledge helps in the standardization of acids and bases.
Volumetric Apparatus
Use volumetric apparatus
We have seen that volumetric analysis involves determinations of quantities of substances, usually acids and alkalis, present in volumes of solutions. This is usually done by using measuring apparatus.
Apparatus used in volumetric analysis is based on volume measurements and since the analysis demands high accuracy, the apparatus has to be calibrated with the highest possible accuracy. It is for this reason that all apparatus for volumetric analysis are specifically for this and not other purposes.
Apparatus used for volumetric analysis include, burette, pipette, burette stand, white tile, conical flask, filter funnel, reagent bottle, watch glass, beaker, measuring cylinder and measuring flask (or volumetric flask). For approximate measurements, measuring cylinders may be used. For accurate measurements of volumes, volumetric flasks are used.
Burette
This is a long glass tube with a narrow lower part, which is fitted with a tap that controls the amount of solution let out of the burette. This instrument is calibrated from 0 to 50 cm3.Before measuring the solution, rinse the burette with distilled water, then with the solution it is going to hold. It has to be filled to the tip and all gas bubbles removed. Thus, the burette is an apparatus used for transferring the solution to the titration vessel (normally a flask).

Pipette
This apparatus has a wider middle part with narrow parts at either ends. The upper narrow part has a mark which marks the volume of all the space below it. If, say, the pipette is one that is marked 25 c

Read More

TOPIC 3 MOLE CONCEPT

          MOLE CONCEPT
The Mole as a Unit of Measurement
The Mole with Other Units of Measurements
Compare the mole with other units of measurements
When carrying out an experiment, a chemist cannot weigh out a single atom, ion, electron, proton or molecule of a substance. These particles are simply very small. A counting unit that is useful in practical chemistry must be used.
The standard unit is called one  mole of the substance. One mole of each of these different substances contains the same number of the particles (atoms, molecules, ions, electrons, protons, neutrons, etc). That number per mole has been worked by several different experimental methods and is found to be 6.0 × 1023. The value 6.0 × 1023 is called Avogadro’s constant or Avogadro’s number and is abbreviated as L. It is named after the nineteenth-century Italian chemist, Amedeo Avogadro.
The value 6.0 × 1023 is obtained through the following relationship.The mass of one atom of carbon-12 is 1.993 × 10-23g. Then, the number of atoms present in 12g of carbon-12 is derived as follows:
1 atom = 1.993 × 10-23g
X atoms = 12g

\ X = 6.0 × 1023 atoms.
Therefore, the number of atoms in 12g of carbon-12 and hence the number of particles in a mole are 6.02 × 1023 atoms.
Hence, Avogadro’s number is the number of atoms in exactly 12g of carbon-12 isotope.One mole of any substance contains as many as many elementary particles as the Avogadro’s number (constant).
So, from the above explanation, the mole can be defined as the amount of a substance that contains as many elementary particles as the number of atoms present in 12g of carbon-12 isotope.
Substance Formula Relative formula mass, Mr Mass of one mole (molar mass) This mass (1 mole) contains
Carbon C 12 12g 6.0 × 1023 carbon atoms
Iron Fe 56 56g 6.0 × 1023 iron atoms
Hydrogen H2 2 × 1 = 2 2g 6.0 × 1023 molecules
Oxygen O2 2 × 16 = 32 32 6.0 × 1023 molecules
Water H2O (2×1) + 16 = 18 18g 6.0 × 1023 formula units
Magnesium oxide MgO 24 + 16 = 40 40g 6.0 × 1023 formula units
Calcium carbonate CaCO3 40+12+(3×16) = 100 100g 6.0 × 1023 formula units
Silicon oxide SiO2 28 + (2 × 16) = 60 60g 6.0 × 1023 formula units
Fe3+ Fe3+ 56 56g 6.0 × 1023 iron(III) ions
Cl- Cl- 35.5 35.5g 6.0 × 1023 chloride ions
e- e- - - 6.0 × 1023 electrons

Read More

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

        

                                   

Read More

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

Read More

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 

Read More

5 BENEFITS OF READING

                                          

Reading has a significant number of benefits and if you're one of countless people who don't
make a habit of reading regularly,you might be missing out.
  NOW;here we GO⇩

1;mental stimulation

the brain requires exercise to keep it strong and healthy,so the phrase "use it or lose it" is particularly applied it when comes to  your mind

2;knowledge

the more you read different books the more you expand your knowledge.And the more knowledge you have the better equipped you are to tackle any challenge you will ever face

3;vocabulary expansion

books and novels are vital for learning different languages,so we get exposed to words (different vocabularies) when we read books

4;you entertain yourself

the best part f entertaining yourself even if you read at night you can visualized the characters in dream too.

5;better writing skills

this goes hand to hand with expansion of your vocabulary.exposure to published,well written work has a noted effect on one's own writing

elimu.




check hii kwa muda wako

 

thanx for reading love this article? share it with your friends

Read More