Verified chemistry WAEC 2018 expo

Verified chemistry obj answers!!! 

Chemistry Obj

1-10: ABDCBCABAC

11-20:DACBBACCAA

21-30: CBCDCDAAAB

31-40: AABACBABAA

41-50: DBBDCBCCDB

(1ai)
Fermentation is the process in which a substance breaks down into a simpler substance. Microorganisms like yeast and bacteria usually play a role in the fermentation process, creating beer, wine, bread, yogurt and other foods.

(1aii)
Zymase

(1b)
-The strength of an acid
-The PH of the solution

(1c)
Fe+H2SO4->FESO4 + H2
H2SO4=10cm^3
Concentration=1mol/dm^3
Amount=Vol * Concentration
=10/100*1
=0.01mol
1mol=56g
0.01mol=56*0.01
=0.56g
Mass of unreacted=5-0.056
=4.44g

(1d)
(i) NaOH(aq)
(ii) Poly-propenitrite

(1e)
A catalyst increases the rate of a chemical by swinging it's activation every. 

(1f)
(i) CH3CooH + NH3 ---->CH3CooH2 + H2O
(ii) Ethanoamide

(1g)
(a) It doesn't corrode easily. 
(b) it doesn't react with contain inside. 
(c) It can stand for a long period of time. 

(1h)
(a) Sweet production industries 
(b) perfume industries. 

(1i) 
(a) Evaporation
(b)seedling

(1j)
(a) it increases the volume water in ocean and seas. 
(b) It causes increase in rainfall and also corrode painted surfaces


5a)
1.Water Gas
2.Producer Gas
ii)Water Gas
iii) Both the hydrogen and Carbon(ii) Oxide in water gas burn in air to release a lot of heat,this makes it a better fuel
Iv)
1.Producer Gas
02(g) + N2(g) + 2C(s)-->2CO(g) +N2 + heat
2.Water Gas
C(s) +H2O(g)-->CO(g) + H2(g)

5ai) 
•To manufacture ammonia 
•Production of fat from vegetation

II) 
Mg(HCO3)2(aq)---->MgCO3(g)+H2O(L)+CO2(g)
i. Temporary hardness 
ii •Waste Soap
   •Furring of kettles

bi)
Oxygen is given off which attract the graphite 

II) 
i•CaO(s)+H20(l)--->ca(OH)2(aq)
ii•used in treating acid soil

5b(i)Thermoplastics can be soften repeatedly by heat and remoulded..
Thermosets cannot be soften or melted by heat and remoulded once they are formed
ii)i.Bakelite
ii.Polythene
iii)
1.Plastic items can be manufactured at very low costs by using moulds and good manufacturing process
2.Raw materials for the manufacturing of plastics are readily and cheaply available from the refining of crude Oil
3.Plastics can be tailor made to our exact requirements, because of wide applications.

(3ai)
 H H H H H 
 | | | | |  
H-C-C-C-C-C-C=C-H  Heptene
 | | | | | |
 H H H H H H

(3aii)  
The  sixth member of Allene C7H14 =
7(molecular mass of carbon) + 14(molecular mass of H) 
= 7(12) + 14(1)
= 84 + 14 = 98gmol-¹

(3aiii) 
-Cracking is the breaking down of higher molecules into smaller molecules while reforming is the change in the functional group or activity of the compound. 
-In cracking more than one product or component is formed. But in reforming one product can still be gotten. 

(3bi) 
Enthalpy of Neutralization change is the heat change which offers when one mole of H+ from an acid reacts with one mole of OH- from an alkali to form one mole of water.

(3bii) 
Weigh about 100cm³ of dil HCL(aq) and that of KOH(aq) of equal volume and put each into a glass calorimeter. The temperature of the two Solutions are taken.  The mean volume of the temperature  of the acid and base taken. Then quickly transfer the alkali to the acid,  turn and take the final temperature of the solution. Record the mass of the mixture. Find the temperature difference. 
Total heat covered = mass × specific heat capacity  × temperature change. 

(3ci) 
I - copper
II - silver 

(3cii) 
Because silver is below copper in the electrochemical series. 

(3ciii) 
Oxidation - anode
Reduction - Cathode
[4/10, 3:54 PM] ‪+234 708 632 5914‬: 5ai) 
•To manufacture ammonia 
•Production of fat from vegetation

II) 
Mg(HCO3)2(aq)---->MgCO3(g)+H2O(L)+CO2(g)
i. Temporary hardness 
ii •Waste Soap
   •Furring of kettles

bi)
Oxygen is given off which attract the graphite 

II) 
i•CaO(s)+H20(l)--->ca(OH)2(aq)

ii•used in treating acid soil


 4aii)
Na2SO3(aq) + 2HCl(aq)----->2Nacl(aq)+H2O(s)+SO2(q)

• 4aiii)

dry the gas evolved by passing it through H2SO4 and collect it by downward delivery
4aiv)
because it is denser than air

4bi)
Dalton's law of partial pressure states that in a mixture of gases, which do not react chemically together, a gas will exert a partial pressure, which is the pressure, it will exert if it is kept alone in the vessel.

4bii)
T1=12degree = 285k
P1=690mm Hg
V1=30cm^3
T2=273k
P2=760mmhg
V2=?
Using the general gas law 
V1P1/T1 = V2P2/T2
V2=30*690*273/285*760
V2=261cm^3
V2=26cm^3

4ci)
Cl2(q)+H2O(i)------>HCL(aq)+HOCL(aq)
4cii)
litmus turn red because of the presence of the acid HCL

4di)
chlorine bromine iodine/increasing boiling point
4dii)
because water has two(2)ion pairs of electrons as compared to ammonia which has one


(2ai)
Collision theory states that the rate of a reaction depends on the rate of collision of the reactant molecules. Hence effective collision determines the rate of the reaction because it is the collision that leads to the formation of a product.

(2aii) 
When the rate of collision increases, the rate at which molecules collide with each other will also increase thereby making the kinetic energy of the molecules to also increase. The temperature will also increase because temperature is a measure of average kinetic energy. 

(2bi)  
Draw your diagram 

(2bii) 
C2H5OH + 3O2 ---->2CO2 + 3H2O
1mole of ethanol = 3moles of O2
2.5moles of ethanol will require 3 × 2.5/1 = 7.5moles of O2. 
but 1 mole of gas = 22.4dm3
7.5moles = 7.5 × 22.4 = 168dm3 of O2. 

(2Ci) 
Esterification is the formation of an Ester by the reaction between Alkanol and an acid.

(2cii) Two uses of alkanols 
(i)  They are used as solvents for cellulose 
(ii) They are uses in making perfumes and cosmetics. 
(iii)  They are used for quick drying of paints and nail varnishes.

(2ciii) 
Sodium Ethanoate 

(2di) 
Tin

(2dii ) 

This is because the galvanized plate is corrosion-resistant. It has a protective coating which prevents further oxidation of the metal.

3a)
From the passage of steam through a mass of hot coke at
a very high temperature (about 1000 oC).
The water gas is mixed with more steam and passed over iron
(III) oxide (as catalyst) at 450 o C. More hydrogen is produced
and carbon(II) oxide gets oxidized to carbondioxide. I.e.
The carbondioxide is removed by dissolving the above products in water under 30 atm pressure - CO2 dissolves.
The gas is then passed through copper(I) methanoate in
ammonia solution under pressure to absorb any trace of carbon(II) oxide which might be present as impurity if not
removed - the hydrogen produced is pure.


3aii)
C (s) + H 2 O(g) → CO (g) + H 2(g)
3aiii)
I. by the action of a dilute strong acid on metals, such as zinc:
Ii. by reaction amphoteric metals with a strong base, such as sodium hydroxide:
Iii. by electrolysis of water:


3b)
I. Decrease in temperature shifts reaction towards product
side.
Ii. increase in pressure shifts reaction towards reactant side.
Iii. Increase in concentration of CO product side.


3ci)
Condensation polymerisation is a process whereby many
small monomer molecules join together to form one large polymer, with water, or some other small molecule formed at the same time.
3cii)
I. polyamides
Ii. polyacetals


3ciii) CH3−COO−CH2−CH3,


3d)
Allotropy is the existence of a chemical element in two or more forms, which may differ in the arrangement of
atoms in crystalline solids or in the occurrence of molecules that contain different numbers of atoms.

3dii)
a) diamond,
b) graphite
3diii)
Diamond is used for cutting hard substance.
Graphite is used to
make brake linings, lubricants, and molds in foundries


 (5a)
DRAW THE GRAPH
(5b)
Movement of goods and services
-Movement of people
-Development of tourism
-Opening up new lands and areas
-Generation of revenue
(5c)
-It is very costly to build and maintain
railways
-Railway transport is relatively slow in
some other areas

-Railway network is generally poor