WAEC GCE CHEMISTRY ANSWERS 2020

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(1a)

(i) Sodium trioxonitrate (v) decahydrate

NaNO₃ . 10H₂O

(ii) Sodium Oxide –> Na₂O

(iii) Potassium tetraoxophospate (v) –> K₃PO₄

(1b)

Products formed are:

Hydrogen gas (a+ cathode)

Chlorine gas (a+ anode)

(1ci)

it decrease down the group

(1cii)

As the atomic radius increases down the group the attraction of the positive nucleus of the electron outer most electron, thus the ionization energy decreases

(1di)

Nitrogen and carbon (ii) oxide

(1dii)

it is used to heat furnace

(1diii)

it is a source of nitrogen for the manufacture of ammonia

(1ei)

Sodium hydrogen – used in qualitative analysis

– Purification of bauxite

(1eii)

Sodium trioxocarbonate (iv)

-Manufacture of glass

-As a water soften

(1j)

2-amino propane

(2a)

MnO₄⁻ + C₂O₄ + H+ –> Mn²+ Co₂ + H₂O

(i) it must be in acidic medium

(ii)

I : C₂O₄²- — Oxidized (reducing Agent)

II : MnO₄⁻ — Reduced (Oxidizing Agent)

(2iii)

MnO₄⁻ + 8H+ + 5e- –> Mn²+ 4H₂O

(2bi)

– Aeration

– Sedementation

– Filtration

– Chlorination

(2bii)

Filtration the water is passed through a filter bed to remove the remaining fine particles of diot

Chlorination: Chorine is added to water to kill germs

(3)

3ai)
¹³R, ⁸Q
¹³R=1s²,2s²,2p⁶,3s²,3p¹
⁸Q=1s²,2s²,2p⁴

(3aii)
¹³R=2,8,3
Valency of ¹³R is 3
⁸Q= 2,6
Valency of ⁸Q=2

(3di)
2H² SO4(aq)+4NaOH(aq)—>2Na² SO4(aq)+4H²O(s)

(3dii)
Sodium teraoxosulphate (iv) salt and water

(3diii)
The resulting solution NaSO4 is basic and will have no effect on litmus paper

(3div)
When heated to dryness it can be used as a dehydrating agent

(3di)
2H² SO4(aq)+4NaOH(aq)—>2Na² SO4(aq)+4H²O(s)

(3dii)
Sodium teraoxosulphate (iv) salt and water

(3diii)
The resulting solution NaSO4 is basic and will have no effect on litmus paper

(3div)
When heated to dryness it can be used as a dehydrating agent

Waec gce chemistry objective answers will be posted here.

CHEMISTRY OBJ

1-10: DDDADBBABA

11-20: CDABDCCDDC

21-30: ACDBDCCDAB

31-40: BCADABDBAC

41-50: ABB

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