PAST WAEC CHEMISTRY QUESTIONS PAPER 2, MAY/JUNE AND OCT/NOV 2007…AS REQUESTED BY OUR READERS

WAEC CHEMISTRY PAPER 2, MAY/JUNE AND OCT/NOV  2007...AS REQUESTED BY OUR READERS

research

MAY/JUNE 2007
Question 1
(a) Define the following terms:
(i) Saturated solution;
(ii)  Solubility. 100

(b)In an experiment to determine the solubility of a given salt Y, the following data were provided:
Mass of dry empty dish = 7.16g =   17.85g
Mass of dish + salt Y  = 9.30g
Temperature of solution =  20oC
Molar mass of salt Y =   100           
Density of solution Y = 1.00gcm-3

Calculate the solubility of salt Y in
(i) g dm-30f solution,
(ii) mol dm-3 of solution. [6 marks]

(c)  State the type of bond broken on melting each of the following substances:                        

NaCl(s);
CO2(s);
SiO2(s);
Al(s) [4 marks]
           
(d) Explain the following observations;
(i) the chemical reactivity of alkali metals increases down the group;
(ii) Mg has a higher melting point than Na;
(iii) K is a better reducing agent than Na. [6 marks]
                      
(e) (i) What is isotopes?
(ii) Lithium exists as 6 Li and 7 Li in the ratio 2:25. Calculate the
                              3           3
Relative atomic mass of the lithium.  [5 marks]

Question 2

(a) Define the following in terms of electron transfer:
(i) oxidation;
(ii) reduction.

Determine the oxidation state of phosphorus in each of the following structures:
(i) POCL3
(ii) PH3

State with reasons whether the following compounds will form acidic, neutral or basic aqueous solutions:
1 NaNO3;
II NH4Cl3;
III Na2C03.        [10 marks]

(b) Consider the set-up

i) What is the gas produced in the experiment illustrated by the set-up above?
(ii) Name the method of collection of the gas.
(iii) Give a reason for your answer in 2(c)(ii) above.
(iv) State the function of the concentrated H2S04 in the conical flask.

(c) Give one
(i). physical property,
(ii). chemical property of the gas.

(d) A 4.3g hydrated tetraoxosulphate (VI) [Na2S04xH20] was heated to remove the water of crystallization. The remaining anhydrous salt had a mass of 2.12g.  Calculate the value of x in the hydrated salt.                   [H=1; O = 16; Na = 23; S = 32]                                   [5 marks]

Question 3

(a) (i) What is a homologous series?
(ii) Give two homologous series present in petroleum.
(iii) Give one sample of a compound belonging to each of the homologous series in 3(a)(ii).
(iv) Name two fractions obtained from the fractional distillation of petroleum.
(vii) Why is there a gradual change in the physical properties of petroleum  fractions? [10 marks]

(b) Write a two-step balanced chemical equations for the reaction of
(i)  ethanol with excess concentrated tetraoxosulphate (VI) acid at high temperature.
(ii)   excess ethanol with concentrated tetraoxosuulphate (VI) acid at lower temperature.

(c) An organic compound of relative molecular mass 46, on analysis was found to contain 52.0% carbon, 13.3% hydrogen and 34.7% oxygen.
(i) Determine its
I. empirical formula,
II. molecular formula.
            
(ii) Draw two possible structures of the compound and name one of them.
  [O = 16, C = 12, H =1]             [9 marks]

Question 4

(a) Write an equation in each case to represent the
(i) B decay of 2~a to give Mg;
(ii) reaction of sodium with cold water.

(b) (i) State two differences between reaction 4(a)(i) and (ii),
(ii) State two applications of the type of reaction represented in 4(a)(i). [4 marks]
Consider the reaction represented by the equation:

Mg(g) +2HCl(aq)        MgCl2(aq) + H2(g)

(c) Name the type of reaction involved.
(ii) Give two ways by which the reaction could be made faster.
(iii) What volume of hydrogen gas would be produced from 6.0g of
magnesium [H = 1; 1 mole of a gas occupy 22.4dm3 at s.t.p]          [6 marks]

(d) What is
(i) n electrolyte,
(ii) electrolysis?

(e) (i) Give one metal that is extracted using electrolytic process.
(ii) Name the ore of the metal.
(iii) What is the substance discharged at  each electrode when dilute NaCI is electrolysed, using graphite electrodes?
(iv Give one industrial use of NaCI.    [7marks]

Question 5

(a) (i) What is the name of the process used for the industrial preparation of tetraoxosulphate (VI) acid?
(ii) State the catalyst used in 5(a)(i).
(iii) Show by means of balanced chemical equations only, the industrial preparation of tetraoxosulphate (VI)acid from sulphur (IV) oxide. [6 marks]

(b) (i) Distinguish between dehydration and drying.
(ii) Explain why concentrated tetraoxosulphate (VI) acid cannot be used to dry ammonia.
(iii) What is the drying agent for ammonia?
(c) (i)Give one example of
        I.  a chloride which is soluble in hot water
        II. a trioxocarbonate (IV) which does not decompose on heating;
        III. an amphoteric oxide.
    (ii) List three methods for the preparation of salts.
    (iii) State one method for the recovery of a salt from its solution.  [7 marks]

(d) (i) State Gay Lussac’s law of combining volumes;
     (ii) Consider the reaction represented by the following equation:

                        C2H4(g) + 3O2(g)           2H2O(g)  +  2CO2(g)
                      
What is the volume of Oxygen required for the complete combustion of 12.5cm3 of ethane.  [5 marks]

Question 6
(a) (i) Draw and label an energy profile diagram of an endothermic reaction.
Indicate on your diagram the
I.   activation energy;
II.  heat change,    H. Explain how the rate of reaction is affected by
addition ofa:catalyst;
increase in temperature.               [8 marks] (b) (i) Write an equation for the thermal decomposition of calcium trioxocarbonate (IV)
(ii) Determine the volume of carbon (IV) oxide measured at s.t.p. that would be produced by the thermal decomposition of 10g calcium trioxocarbonate (IV).
                        [Ca = 40; O = 16; C =12]          [5 marks] (c )(i) Give one use of each of the following forms of carbon:
I. coal;
II. wood charcoal;
III. carbon (IV) oxide. (ii) Write a balanced chemical equation to Show what happens when each of the following compounds, is heated strongly.
I.  Na2C03(s)
II. MgC03(s). (d) Consider the following compounds:
CaO, CaC03 , Ca(OH) 2 ,NaOH.
Which of them is
(i) used ID the manufacture of cement;
(ii) used to detect the .presence of carbon (IV) oxide;
(iii) used to liberate carbon (IV) when dilute acid is added;
(iv) hygroscopic;
(v) deliquescent?                [5 marks]OCT/NOV 2007Question 1(a) (i) State two observations and corresponding conclusion that can be drawn  from J. J. Thomson’s Cathode ray experiment.

(ii) Name the particles generated in the cathode ray experiment.
(iii) Mention two other fundamental particles in an atom.  [7 marks]

(b) Consider the following table showing certain properties of W, X and Y  

 Substance

Conducts electricity when solid

  Melting point
         (0C)
  Soluble
  in water
     W           No

808

     Yes
     X          Yes

3377

     No
     Y          No

35 – 50

     No

i) Indicate in each case the nature of bond present in W,  X and Y.
(ii) Give a reason why

        W does not conduct electricity in the solid state;
        X conducts electricity in the solid state;
        Y cannot be a pure substance.

(iii) Outline how a mixture of  W and Y can be separated. [13marks]

(c) (i) Explain why graphite is used as a lubricant.
(ii) State the function of each of the following substances in the laboratory preparation of dry carbon (IV) oxide:

        potassium hydrogen trioxocarbonate (IV) solution;
        fused calcium chloride. [5marks]

Question 2

(a) An organic compound has the molecular formula C3 H8 O.
(i) Write two possible structural isomers of the compound.
(ii) What class of organic compound are the two isomers?   [4 marks]

(b) Consider the given flow chart

 (FLOW CHART WOULD BE PROVIDED LATER)                                                                                                               

(i) Name the substance and the conditions necessary for fermentation to take place.
(ii)  I. State the gas that is produced during the fermentation
        II.  Describe a test for the gas produced

(iii) Give the names of the substances Q, R and S.
(iv) Write a balanced equation for the reaction between ethene and bromine. [10 marks]

(c) Consider the compound with the structure

    What is the name of the compound?
    Give two reagents that can be used in a test to show that the compound is unsaturated.
    Write an equation for the reaction between bromine and the compound.
    Calculate the mass of bromine required to completely react with 7.0g of the compound.
    [7 marks]

(d)        Alaxin (C5H8)nO is a new drug used for the treatment of malaria.
            Determine the molecular formula of alaxin if its relative molecular mass is 284.
[H = 1, C = 12, O = 16]   [4 marks]

Question 3

(a) (i)  Define each of the following terms:

  1. mole;
  2. concentration.

(ii) Consider the following equation:
2Mg(s) + O2(g) →  2MgO(s) ;
Calculate the mass of magnesium oxide that would be produced by one mole of magnesium
                        [  Mg = 24,  O = 16]    [7 marks] (b) (i) Write a balanced chemical equation for the reaction between chlorine gas and iron (II) chloride solution.

(ii) State the reaction in 3(b)(i).  Give a reason for your answer.
(iii) State what would be observed if acidified KMnO4 is added to iron (II) chloride solution.   [7 marks]

(c) State one industrial application of each of the following methods of separation.
(i) crystallization;
(ii) filtration;
(iii) fractional distillation.   [3 marks]

(d) Name the precipitate formed when aqueous solutions of the following pairs of compounds are mixed:

(i) NaCl and Ag NO3 ;
(ii) K2SO4 and Ba Cl2;                
(iii) Pb(NO3)2 and Na2 CO3 .   [3 marks]

(e) (i) List three characteristic properties of transition metals.   
(ii) Which of the following metals belong (s) to the first transition series?
  Chromium, Lead, Manganese, Aluminium, Sodium. [5 marks]

Question 4

(a)(i) The following equation represents the decomposition of phosphorus (V) chloride.           
                        PCl5(g) ><   PCl3(g) + Cl2(g);  ΔH  = +ve
           
What would be the effect of each of the following conditions on the equilibrium position?

I. Removal of chlorine
II. Decrease in pressure
III. Decrease in temperature
IV. Increase in temperature.

(ii) Under what condition would a reversible reaction be said to attain a state of dynamic equilibrium?
    [6 marks]

(b) The sketch below illustrates the energy profile diagram of a certain reaction

(i) Identify W, X, Y and Z.           
(ii) State the type of reaction represented by the sketch.  Give a reason for your answer.

(iii) Under what condition can be value of W be reduced? [7marks]

(c) (i) Using equations only, show the processes involved in the  extraction of iron and the removal of impurities in the blast furnace.      
(ii) The following reaction occurs when a piece of iron is exposed to moist air for some days.          
                                    4Fe(s) +  3O2 +  xH2O  →  2Fe2O3 .xH2O(s)         
                        State three methods by which this reaction can be prevented.
                                                                                                                             
(iii) What is the oxidation number of iron in the product in 4 (c)(ii) above?  [8marks]
                 
(d) (i) Give one reason why gases deviate from ideal gas behaviour.
(ii) State one condition under which a gas behaves ideally.
(III) Draw a sketch to illustrate Boyle’s law.  [4 marks]

QUESTIONS 5 AND 6 NOT AVAILABLE

Question 7

(a) (i)  Define each of the following terms:

    allotropy;
    isotopy.

(ii)  Name two elements each that exhibit

    allotropy
    isotopy. [8 marks]

(b) Write a balanced chemical equation to show the reaction between carbon (iv) oxide and

 (i) water;
 (ii) burning magnesium;
 (iii) alkali. [6 marks]

(c) The table below shows some solutions and their pH values

   Solution   A    B     C     D     E
      PH  1.2    7    12    6.5   7.8

 

(i) State which of the solutions would

    react with zinc to liberate hydrogen;
    change the colour of phenolphthalein to pink;
    not change the colour of litmus paper.

(ii) Which of the solutions is   

    strongly acidic;
    strongly alkaline?   [7marks]

(c) Explain why aqueous solution of Na2CO3 is basic while aqueous solution of KCl   is neutral.   [4 marks]

Question 8

(a) Distinguish between
(i) a normal salt and an acid salt.  Give an example of each salt.
(ii) a hygroscopic substance and a deliquescent substance.
            Give an example of each substance.  [8 marks]

(b) Solutions of H2SO4 and NaOH of equal concentration were prepared separately.

(i) Write a balanced equation for the formation of the

    acid salt;
    normal salt, from their reaction.

(ii) Calculate the volume of the NaOH that would be required to react with 20cm3 of the H2SO4 in order to form a normal salt.  [5 marks]

(c) An aqueous solution of copper (II) chloride is electrolysed using graphite electrodes.
(i) List the ions present in the electrolyte.
(ii) Which ions would be discharged at the

    anode;
    cathode?.

(iii) Write a balanced equation for the reaction at each electrode.

    What substance would be left after the electrolysis?
    State the effect of the substance on litmus paper.
    Give one industrial use of electrolysis.  [10 marks]

(d) Give one difference in each case between
(i) fine chemicals and heavy chemicals
(ii) thermoplastics and thermosetting plastics. [2 marks]

SOURCE: WAEC

10 comments on “PAST WAEC CHEMISTRY QUESTIONS PAPER 2, MAY/JUNE AND OCT/NOV 2007…AS REQUESTED BY OUR READERS

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s