2019 WAEC Chemistry Obj and Theory Questions and Answers

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CHEMISTRY OBJ

1-10: BCACDADACA
11-20: DDCADAACBA
21-30: BCABBDDBAA
31-40: DDCBDCDBCB
41-50: BACBCCBDDD

QUESTION 3
o. limestone is healed to generate to for the
reaction: Caco entaO +Go,is

() Ammonia is used to make brine

N 4s + CĐ, 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

(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

(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

5…

(a) (i) – filling of weather balloons

3aii)

In the first, ammonia bubbles up through the brine and is absorbed by it. In the second, carbon dioxide bubbles up through the ammoniated brine, and sodium bicarbonate (baking soda) precipitates out of the solution. Note that, in a basic solution, NaHCO3 is less water-soluble than sodium chloride.

Equation
NaHCO3 — CL+02
3ai)

Equation
NH3+NACL(AQ)— 2NACL
3aii)

In the first, ammonia bubbles up through the brine and is absorbed by it. In the second, carbon dioxide bubbles up through the ammoniated brine, and sodium bicarbonate (baking soda) precipitates out of the solution. Note that, in a basic solution, NaHCO3 is less water-soluble than sodium chloride.

Equation
NaHCO3 — CL+02
4a πŸ‘‡

Gold extraction refers to the processes required to extract gold from its ores. This may require a combination of comminution, mineral processing, hydrometallurgical, and pyrometallurgical processes to be performed on the ore.Gold mining from alluvium ores was once achieved by techniques associated with placer mining such as simple gold panning and sluicing, resulting in direct recovery of small gold nuggets and flakes. Placer mining techniques since the mid to late 20th century have generally only been the practice of artisan miners. Hydraulic mining was used widely in the Californian gold rush, and involved breaking down alluvial deposits with high-pressure jets of water. Hard rock ores have formed the basis of the majority of commercial gold recovery operations since the middle of the 20th century where open pit and or sub-surface mining techniques are used.

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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

No5

(i)It is currently being used in many industries, from chemical and refining to metallurgical, glass and electronics.

ii……
3ai)
The Solvay Process is a continuous
process using limestone (CaCO 3 ) to produce carbon dioxide (CO 2 ) which reacts with ammonia (NH3 ) dissolved in brine (concentrated NaCl(aq)) to produce sodium carbonate.

3aii)

In the first, ammonia bubbles up through the brine and is absorbed by it. In the second, carbon dioxide bubbles up through the ammoniated brine, and sodium bicarbonate (baking soda) precipitates out of the solution. Note that, in a basic solution, NaHCO3 is less water-soluble than sodium chloride.

Equation
NaHCO3 — CL+02

: 3ai)

Equation
NH3+NACL(AQ)— 2NACL

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2019 WAEC CHEMISTRY OBJ $ THEORY QUESTIONS AND ANSWERS

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