WAEC Chemistry Obj and Essay Answer – 2019 May/June Expo

Chemistry Essay/Theory 

CLICK HERE FOR NUMBER 4

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CLICK HERE FOR NUMBER 3
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CLICK HERE FOR NUMBER 3 CONT
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(1a) 
– High temperature of 4500degree(c) or more 
– High pressure 
– Catalyst 
(1b)
– For decoration
– For protection 
(1c)
Calcium oxide (Cao) is alkaline and Hcl is acidic. The two react to form calcium chloride and water; instead of dry Hcl after that, it will end up with wet calcium chloride
(1d) 
This is an oxidation reaction. The acid oxidizes the iron (II) sulphate to iron (III). The baron gas evolved is Nitrogen (IV) oxide
(1ei)
(i) Zinc oxide with H2SO4
ZnO(s) + H2SO4 —> ZnSO4(aq) + H2O(l) 
(ii) Zinc oxide with sodium hydroxide solutions 
ZnO(s) + 2NaOH(aq) —> Na2ZnO(aq) + H2O(l)
(1eii)
Amphoteric property 
(1f) 
(i) Have the same atomic number 
(ii) Have different mass numbers
(1g)
– Hcl 
-O2
(1h)
(i)H2S
(ii)SO2
(1i)
It is the average mass of atoms of the element on which one atomof carbon
It is the number of times the average mass of one atom of the element is heavier than 1/12th of the mass of one atomw carbon 12
(1j)
(i) The concentration of thereactants and products are equal
(ii) The rate of the forward reaction is same as rate of the backward reaction
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(2a)
(i)C10H22—–>(cracking)—->C6H14 + C4H8
P is C4H8
(ii)
H H H H
| | | |
H-C=C-C-C-H
| |
H H

H CH3 H
| | |
H-C= C- C-H
|
H
(iii)

(2b)
Hundi’s rule:Electrons occupy each orbital singly first before pairing takes place in a degenerated orbital
Aufbau’s principle:Electrons enter into orbitals in order of increasing energy
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QUESTION 3
o. limestone is healed to generate to for the
reaction: Caco entaO +Go,is

() Ammonia is used to make brine

N 4s + CD, ca) + 1 OLA) N 1, HC0% ( )
NHy H CO Nacles NaHo tNde

LOG) Chiz O6.com Zymase 325 H,OH(aq) + 2002 92

mounts
GI On fermenting the con released to pressure
in the bottle and t shatters

6)
Cu, Fe, Na, K
increasing reactivity
GT) Sodhim (Na)
C, and Fe
os A redox reaction & on oxidation – reduction
reaction, both occur at the same time

(7) I. Redox
I. Not Reddit.
TV Not Reduce
Not Rederc
v Redo
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5…

(a) (i) – filling of weather balloons
– manufacture of plastics
– manufacture of ammonia by the Haber process
– manufacture of methanol
– oil refinery process / hydrocracking
– used in fuel cells
– manufacture of margarine
– in oxy-hydrogen flame (for welding and cutting metals}
– as reducing agent in production of metals e.g. Cu and Pb from their oxides
– conversion of coal to crude oil
– (liquid) hydrogen is used as rocket fuel / gaseous fuel
(ii) I. – temporary hardness of water
II. – scales / furring of kettles / pipes cause blockage leading to power wastage
– soap is wasted / not suitable for laundry
– not suitable for use in tanning, textiles and paper production

5(b) (i) at high temperatures oxygen gas produced at the anode reacts with the
graphite electrodes to form carbon (IV) oxide
(ii) I. CaO + H2O › Ca(OH)2
II. – used to treat acidic soil
– used to make mortar/plasters/cement/hold bricks
– in manufacture of glass
– purification of water/removing hardness of water
– manufacture of white wash
– to test for CO2
– production of bleaching powder
– to recover / produce ammonia from ammonium chloride/ used in solvay process

5(c) (i) Is the alkaline hydrolysis of fats/oils to produce soap ( and propane- 1,2,3 triol)
OR
The process in which fat or oil is boiled with alkali to produce soap (and propane -1, 2, 3-triol)
(ii) oil / fat and alkali (sodium hydroxide / potassium hydroxide)
(iii) propane-1,2,3-triol
Bottom of furnace

5(d) (i) The O2 in the hot air combines with carbon (Coke) to produce carbon (IV)
Oxide which is reduced to carbon (II) oxide.
C + O2 › CO2
CO2 + C › 2CO
Middle of furnace
(ii) The CaCO3 decomposes under great heat to form CO2 and CaO / CaCO3 decomposes to remove the impurities / SiO2
CaCO3 › CaO + CO2
CaO + SiO2 › CaSiO3
Top of furnace
(iii) Iron (III) oxide is reduced to metallic Iron
Fe2O3 + 3CO > 2Fe + 3CO2
OR
Fe3SO4 + 4C0 — 3 Fe + 4 CO2