WAEC CHEMISTRY ANSWERS

CHEMISTRY OBJ:
1-10: ADADACDCBC
11-20: DCCBCDBCBA
21-30: CDCBCCDDCC
31-40: DBAAABBDBC
41-50: DCCDCCBBAA

1a) Esterification is the reaction between organic acid e.g ethanoic acid and organic base e.g ethanol to produce salt e.g alkanoate and water

(1b) -Low melting point -Low thermal capacity

(1b) Duralumin cosist of aluminium,magnesium amd manganese

(1d) -Raw materials is the chemical or physical materials in its natural or uncombined form -Primary product is the useful product during chemical reactions

(1e) Charles law states the volume of a fixed ma$$ of a gas is directly proportional to the temperature provided pressure remains constant

(1f) -Eye shades -Laaboratory coats -Hand gloves -Spatula

(1g) -Ammonia is used as a refrigerant in refrigerators -Ammonia is used in production of amine and amide

(1h) -Cracking -Sodium Ethanoate –

(1i) H2S04=0 (1*2)+S+(-2)4=0 2+S-8=0 S-6=0 S=6

(1j) -Sodium trioxochlorate(v) -Copper(ii)tetraoxosulphate pentahydrate

(2a)
(i)
-J
-Q,X,Y
-X
-Q

(ii)
Ionic bond

(iii) Number of neutrons in Q

(iv)
X(^+) + R(^-2) -> X2R

(v)
R

(vi)
Y

(2b)
(I)

(i)
The atomic orbitals are the group of orbitals such as S-orbitals and D-orbitals for filling electrons

(ii)
-Atoms are made up of small indivisible particles

-Atoms of the same elements are chemically alike and different from atoms of different element

-When atoms combine together they do so in simple ratio

(II)
It does not obey the law of radioactivity

(iii)
It contains protons,neutrons and electrons

(2c)
(i)
C(s)+O2(g)->CO2(g)
Volume of carbon
1/(30*60)*0.50=V/22.4
Volume of carbon =(0.50 *22.4)/(30*60)
=(6.2*10^-3)/44dm^3
=1.4*10^-4dm^3

(ii)
mole of oxygen=(1.4*10^-4)/22.4
=6.3*10^-6dm^3

 

3a)
i)
-Each member of a family has the same general molecular formular
-Each member of a family has the same method of preparation
-Each member differs in its molecular formular by CH2
ii)
Alkanes, Alkynes

 

3b)
i)Hydroxyl group
ii)C2H5OH
iii)C2H5OH + CH3COOH->CH3CooC2H5 +H2O
iv) Ethyl ethanoate
3c)(—) means tripple bond do not write
i)
C2H2 + Br2-> H-C (—) -> C-H+Br-Br -> H-C(Br) =C(Br)-H
ii)
1,1,2,2, – tetrabromoethane
iii)
-High temperature
-Presence of catalyst

 

3d)
i)
Preparation of ethanol from starch starts with fermentation .The starch granules is extracted from starch food stuff by hydrolysis and addition of enzymes.It is broken to dissacharide by adding amylase
(C5H6O6)->(nH20)->C12H24O12
The maltose is formed is further broken down to fructose and glucose
Maltose=fructose + glucose By using maltase
The monnossacharide is then broken down to ethanol and carbon(iv) oxide by adding zymase
C6H12O6->(zymase)->C2H5OH+CO2
ii)
-It contains grant molecules
-it is polysaccaride
iii)
Starch does not reduce felhing solution because it is not a reducing agent
iv)
To the unknown substance containing the starch, add iodine solution if it turns blue black, then this confirm the presence of starch

 

5a)
i),hydrogen chloride
ii)
-They are soluble in water
-They are less dense than air

 

5b)
i)
-Solubility is the amount of solute of moles in which can dissolve in 1dm^3 of solvent at standard temperature and pressure
-Sateurated solution is the solution in which contains more solute than it can dissolve at a particular temperature
ii)
-Temperature
-Surface area of solid
iii)
Given;

mass of Z=10.2g
Volume(V)=15.4cm^3
Temperature=40degreesC
Molar mass of  Z=331
Mole=10.2g/331gmol
Solubility=Mole/Volume
=0.031/(15.4*1000)
=2*10^-6mol/dm^3

 

5c)
i)
– P is Ca^2a+,Calcium ion
Q is magnesium ion
Ca^(2a+)+H2(^+) + O2(^2-)->Ca(OH)2
ii)
To the unknown substance in the container,add copper(II)tetraoxosulphate(IV)solution, If a blue precipitate is formed.This confirms the presence of water
iii)
-Furring of kettle and boiler
-Stalagmite and Stalactite
iv)
Na2SO4 + Ca(OH)2->CaSO4 + NaOH

 

 

 

 

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14 Comments

  1. 2a)
    i)-J
    -Q,X,Y
    -X
    -Q
    ii)Ionic bond
    iii) Number of neutrons in Q
    iv) X(^+) + R(^-2) -> X2R
    v)R
    vi)Y
    2b)
    I)
    i)
    The atomic orbitals are the group of orbitals such as
    S-orbitals and D-orbitals for filling electrons
    ii)
    -Atoms are made up of small indivisible particles
    -Atoms of the same elements are chemically alike
    and different from atoms of different element
    -When atoms combine together they do so in simple
    ratio
    II)
    It does not obey the law of radioactivity
    iii)
    It contains protons,neutrons and electrons
    2c)
    i)
    C(s)+O2(g)->CO2(g)
    Volume of carbon
    1/(30*60)*0.50=V/22.4
    Volume of carbon =(0.50 *22.4)/(30*60)
    =(6.2*10^-3)/44dm^3
    =1.4*10^-4dm^3
    ii) mole of oxygen=(1.4*10^-4)/22.4
    =6.3*10^-6dm^3

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