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2020 WAEC GCE 1ST SERIES CHEMISTRY OBJ & THEORY QUESTIONS AND ANSWERS

CHEMISTRY OBJ

1-10: DDDADBBABA

11-20: CDABDCCDDC

21-30: ACDBDCCDAB

31-40: BCADABDBAC

41-50: ABB

 

 

 

(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

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(3)

 

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