Neco 2020/2021 Chemistry obj & Theory Question and Answers Verified Expo

NECO-2020-CHEMISTRY-ANSWERS

You Are To Answer Four (4) Questions
Only. We Answered. FIVE (5) Pls Answer Four(4). Enjoy And Tell People About Us.
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11BDEABDBCEE

21DEEECCCCEC

31ABDAADCAAB

41EDEDAEADDD

51DBEBABBADA

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(1ai)
(i)graphite
(ii)diamond

(1aii)
(i)animal charcoal
(ii)carbon black

(1aiii)
(i)The property of elements are a periodic function of their atomic number
(ii)Elements are arranged in the periodic table according to the order of increasing in their atomic weight.

(1bi)
Periodicity can be defined as the trend or recurring variation in element properties with increasing atomic number.

(1bii)
using; mole = no; of atoms/avogadro’s constant
0.5=no; of atoms/6.023*10²³
no; of atoms = 0.5*6.02*10²³=3.012*10²³atom

(1ci)
Faraday’s first law of electrolysis state that the chemical deposition due to the flow of current through an electrolyte is directly proportional to the quantity of electricity (coulombs) passed through it.

(1cii)
2O²^- + 9^e —>2O²
no; of electron = 4
Q=20300C
G.M.V =22.4dm³.
F=96500C
Mole=Q/n,f
Mole=20300/4*96500
Mole=20300/386000
Mole=0.05mol
Recall; =vol/G.M.V
0.05=vol/22.4
vol=0.05*22.4
vol=1.12dm³

(1di)
Using H²SO⁴
H+ SO⁴^-¹
H+ OH^-
A+ Anode
OH —-> OH + e^-
2OH+(aq)+2OH(aq)—->2H²O(s)+O²(aq)

(1dii)
Tabulate
-Electrolyte- (I)teraoxosulphate(iv)acid
(II)Ester

-non electrolyte-
(III)phenol

(1ei)
(i)mercury

(1eii)
(I)no; of electron in Y =16
(II)no; of mass number =16+18=34
(III)sulphur
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(2ai)
basicity can be defined as the number of replaceable hydrogen ion in an acid

(2aii)
(I) —> 3
(II) —> 1
(III) —> 2

(2bi)
(i)Concentration
(ii)Temperature
(iii)Pressure

(2bii)
(i)Light
(ii)Temperature
(iii)Nature of reactant

(2ci)
Tabulate
S/N; (I), (II)

Indicator; methyl orange, phenolphthalein

Colour in acid; red, colourless

Colour at end point; orange colourless

Colour in base; yellow, pink

Suitable for; strong acid and weak base, weak acid and strong base

(2cii)
(i)Nitrogen —> 1s²,2s²,2p³
(ii)Fluorine —> 1s²,2s²,2p⁵
(iii)Aluminum —> 1s¹,2s²,2p⁶,3s²,3p¹

(2di)
(I)Hydrogen gas is liberated
(II)The purple colour turns colourless
(III)It leads to the deposit of black residue of carbon

(2dii)
(i)It serve as immediate source of energy
(ii)it is used in the manufacture of sweets.
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(4ai)
(I)Burning requires heating while corrosion does not
(II)Boiling occurs at a certain temperature while evaporation occurs at all temperature

(4b)
A concentration solution can be defined as a solution formed when a large quantity of a substance dissolves in a little volume of water

(4bii)
(i)position of ion in electrochemical series
(ii)concentration ion
(iii)nature of electrodes

(4ci)
Al²(SO⁴)³=(27*2)+(32*3)+(16*12) =54+96+192=342glmol

(4cii)
Aluminum teraoxosulphate (iv)

(4ciii)
(i)Propane – 1,2,3,- triol
(ii)Potassium salt

(4di)
Tabulate.
-Soaples detergent-
(i)it does not form scum in hard water
(ii)they are non-biodegradale

-Soapy detergent-
(i)It firm scum in hard water
(ii)They are biodegradable

(4dii)
(i)RCOOH
(ii)ROH

(4diii)
V1=300cm³.
P1=760mmHg
P2=800mmHg,
V2=?
Using; V1*P1 =V2*P2
300*700=V2*300
V2=300*760/800
V2=228000/800
V2=285cm³

(4div)
Its change is +3

(4dv)
Al³^+ (Aluminum ion)
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