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Edu : Waec 2018 Chemistry Objectives & Theory Expo Answers

Views: 1284 Posts: 1 Started By: oladamats Last Poster: donsmart142 Last Post Date: Apr 10, 2018
1 1 Total
Apr 10 ( Post 1 )



Due to wat happen recently, i have no time to sort answers, we match all west africa answers together to save time pls check very well and pick urs, all answers are correct..... Thank You
Chemistry Obj
1-10: ABDCBCABAC
11-20:DACBBACCAA
21-30: CBCDCDAAAB
31-40: AABACBABAA
41-50: DBBDCBCCDB

1a)
Compound is a chemical substance composed
of many identical molecules (or molecular
sentities) composed of atoms from more than
one element held together by chemical bonds.
1b)
i. Initiation
Ii. Hydrogen abstraction
1c)
i. Iron
Ii. cobalt
1di)
Zn(s) + 2AgNO3--->Zn(NO3)2 + 2Ag(s)
(1dii)
I. Ag is reduced
II. Zn is oxidized
(1e)
16
O - 90% abundance
8
16
O - 10% abundance
8
= The relative atomic mass Ar = (16×90/100) +
(18×10/100)
= 1440/100 + 180/100 = 1440+180/100
= 1620/100 = 16.20
(1f)
The ores of iron are:
-Hematitie(Fe2O3)
-Magnetide(Fe3O4)
(1gi)
Biotechnology is the optimism exploitation of
biological processes for industrial and other
purposes. It is the branch of science that
exploits microorganisms fot the production of
antibiotics, hormones, etc.
(1gii)
Antibiotics
(1h) An element is a substance which can not
be further divided by an ordinary chemical
reaction.
(1i)
- fossil fuel for burning
- Biomass burning
- wetlands
(1j)
It is because the dipole induced dipole bonds
are stronger in iodine than in bromine and than
in chlorine ie there are more electrons in
iodine than in bromine and that in chlorine
(2a)
It means that the standard electrode potential
difference set-up between Zinc and one-molar
solution of its ion at 298K
(2b)
(i) Zn²(Aq) + / Zn(s) ---- cathode
Cu/ Cu²+(aq) ------- anode
(ii) Zn²+(aq)/Zn(s) // Cu / Cu²+
(iii)
At the cathode ---- reduction
At the anode ----- Oxidation.
(iv) EΦ = EΦ - E
= 0.34-(-0.76)
= 0.34+0.76
= +1.10V
(2ci)
- Chemical and allied products industries
- sunshine oil and chemical industries
- Eleme petrochemical industries
(2cii) source of raw materials
Nearness to market
Source of amenities
(2ciii)
-Pollution of air (surrounding)
-Land excavation and improper with disposal
(2di)
Ag2O(s) +H2O2= 2Ag(s)+ O2(g)+H2O(l)
(2dii)
H2O2 + Cl2 => 2HCl(g) + 2H2)(l)
(2e)
-It is an inert gas
-It is slightly denser than air
-It is slightly soluble in water
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)
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.
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)
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)

Go Below For More Answer



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.
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
=================
1a) Fermentation is
the chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, typically involving effervescence and the giving off of heat.
=========
4 ai)
DIAGRAM
4 aii )
Na 2 SO3 ( aq ) + 2 HCl ( aq ) - - - - - > 2 Nacl ( aq ) + H 2 O( s ) + SO2 ( q )
4 aiii)
dry the gas evolved by passing it through H 2 SO4 and collect it by downward delivery
4 aiv )
because it is denser than air
4 bi)
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 .
4 bii )
T1 = 12degree = 285 k
P 1 = 690 mm Hg
V 1 = 30cm^ 3
T2 = 273 k
P 2 = 760 mmhg
V 2 =?
Using the general gas law
V 1 P 1 / T1 = V 2 P 2 / T2
V 2 = 30* 690 * 273 / 285 * 760
V 2 = 261 cm^ 3
V 2 = 26cm^ 3
4 ci )
Cl2 ( q ) + H 2 O( i ) - - - - - - > HCL ( aq ) + HOCL ( aq )
4 cii )
litmus turn red because of the presence of the acid HCL
4 di )
chlorine bromine iodine / increasing boiling point
4 dii )
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.
====================
(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


















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02:59 Tue, 10 Apr 2018 ( Post 123 )
Pls No 4 and obj 41-50

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