NECO Chemistry Questions 2020 Objective and Theory Latest Update

NECO Chemistry Objective Answers:

1-10 DCBBCBBEDC

11-20 CADECEBBDC

21-30 EEBABDADBE

31-40 AECCACDDDC

41-50 DABABCBBCA

51-60 CBBAABCADE

1ai)

A mixture contains two or more constituents which can easily be seperated by physical methods

1aii)

magnesium trioxonitrate(v) = Mg(NO3)2

molar mass of Mg(NO3)2

=(1*24) + 2 (14*1 + 16*3)

=24 + 2 (14 + 48)

=24 + 28 + 96 = 148g/mol

% of nitrogen = 2*24*100/148

% of nitrogen = 48*100/148

% of nitrogen = 4800/148

% of nitrogen = 32.43%

1aiii)

i)calcium oxide (CaO)

ii)calcium choride (CaCl2)

1bi) CnH2n+1OH

1bii) hydrolysation

1biii)

i)displacement reaction

ii)double decomposition reaction

iii)decomposition reaction

iv)catalytic reaction

v)reversible reaction

1biv)

i)endothermic heat change

ii)exothermic heat change

1ci)

i)methyl orange

ii)phenolphthalein

iii)litmus

1cii) NH4Cl+Ca(OH)2—–>CaCl2+2NH3+2H2O

1ciii) it is collected by upward delivery

1civ) mass of gas = 1.58*22.4 = 35.392

        vapour density = 35.392/1

        relative molecular mass= V . D * 2 =35.392*2

        relative molecular mass= 70.784

==================================

5ai)

i)carbon monoxide and hydrogen

ii)carbon monoxide,carbon dioxide,hydrogen and nitrogen

5aii)

i)colloids is an intermediate between true solution and a suspension

ii)condensation is the process by which water vapour in the air is changed to liquid water

5bi) CaC03+2HCl—–>CaCl2+H2O+CO2

5bii)

i)it is used in fire extinguishers

ii)it is used in the manufacturing of mineral water

iii)carbon(iv)oxide is used as a coolant in nuclear reactors

5biii)

i)Cr2O7^-2 =2Cr + C-2*7) = -2

  2Cr – 14 = -2

  2Cr = -2 + 14

  2Cr/2 = 12/2

  Cr = 6

ii)Cr2{SO4}3

   2Cr + 3 (-2*1 + -2*4) = 0

   2Cr + 3 (-2 – 8) = 0

   2Cr + 3 (-10) = 0

   2Cr – 30 = 0

   2Cr/2 = 30/2

   Cr = 15

5ci)

vulcanization is a chemical process of converting neutral rubber or related polymers into more durable materials through the addition of sulfur or other equivalent curatives or accelerators

5cii)

Time Taken(t) for 6.35g of copper(ii)tetraoxosulphate

solution

Cu^2^+ + 2c ——->Cu

Q = 2*63.5*95600

Q = 12255500

Q = 1t

12255500/10 = 10*t/10

t = 1225550/60 = 204258.3

5ciii)

Latex

==================================

4ai)

electrolytic cell is a cell that consist of a container of electrolyte with two electrodes connected to a suitable direct current supply

4aii)

i)daniel cell

ii)Leclanché cell

4aiii)

i)copper

ii)tin

4aiv)

action of dilute acide on zinc

4av)

Zn+2HCl——>ZnCl+H2

4bi)

i)dinitrogen(i)oxide(N2O)

ii)nitrogen(v)oxide(N2O5)

iii)nitrogen(iv)oxide(NO2)

4bii)

charle’s law states that the volume of a fixed mass of gas varies directly with the absolute(kelvin)temperature provided the pressure remains constant.

4biii)

P1 V1 = P2 V2

given that

P1 = 900mmHg

P2 = 750mmHg

V1 = 300cm^3

V2 = ?

V2 = P1V1/P2

V2 = 900*300/750

V2 = 270000/750

V2 = 360cm^3

4biv)

% composition carbon

= 12/(12*6) + (1*6) *100%

= 12/72+6 *100

= 12/78 * 100% = 1200/78%

%composition of carbon = 15.38%

4c)

TABULATE

-THERMOPLASTS-

i)it melts when heat is applied to it

ii)highly recycled

-THERMOSETS-

i)does not melt when heat is applied

ii)cannot be recycled

==================================

2ai)

ionization energy deals with electron loss while electron loss while electron afinity deals with electron gain

2aii)

i)they are used to dry gases

ii)they are used to recover valuable vapours from industrial effluents and refine petroleum

2bi)

TABULATE

-RHOMBIC SULPHUR-

i)bright yellow in colour

ii)it is octohedral in shape

-MONOCLINIC SULPHUR-

i)amber in colour

ii)it is needle like in shape

2bii)

oxygen = 60%

sodium = 40%

oxygen 60/16

3.75/1.74 = 2

sodium 40/23

1.74/1.74 = 1

the emperical formula is NaO2

2biii)

sodium(iv)oxide

2ci)

i)x is hydrophobic region

ii)y is hydrophilic religion

2cii)

i)for laundry purpose

ii)for fuel

2ciii)

i)the distance of outermost electron from the nucleus

ii)the size of the positive nuclear charge

iii)the screening effect of inner electrons

2civ)

period law states that the properties of the elements are a period function of their atomic number

2di)

n—pentane—–>n—butane—–>2—methylbutane—2,2—dimethylpropane

2dii)

i)glucose

ii)galactose

==================================

Completed. enjoy.

CHEMISTRY OBJ : 1-10 DCBBCBBEDC 11-20 CADECEBBDC 21-30 EEBABDADBE 31-40 AECCACDDDC 41-50 DABABCBBCA 51-60 CBBAABCADE

1ai) A mixture contains two or more constituents which can easily be seperated by physical methods

1aii) magnesium trioxonitrate(v) = Mg(NO3)2 molar mass of Mg(NO3)2 =(1*24) + 2 (14*1 + 16*3) =24 + 2 (14 + 48) =24 + 28 + 96 = 148g/mol % of nitrogen = 2*24*100/148 % of nitrogen = 48*100/148 % of nitrogen = 4800/148 % of nitrogen = 32.43%

1aiii) i)calcium oxide (CaO)

ii)calcium choride (CaCl2) 1bi) CnH2n+1OH

1bii) hydrolysation

1biii) i)displacement reaction ii)double decomposition reaction

iii)decomposition reaction iv)catalytic reaction v)reversible reaction

1biv) i)endothermic heat change ii)exothermic heat change

1ci) i)methyl orange ii)phenolphthalein iii)litmus 1cii) NH4Cl+Ca(OH)2—–>CaCl2+2NH3+2H2O 1ciii) it is collected by upward delivery 1civ) mass of gas = 1.58*22.4 = 35.392 vapour density = 35.392/1 relative molecular mass= V . D * 2 =35.392*2 relative molecular mass= 70.784 ==================================

5ai) i)carbon monoxide and hydrogen ii)carbon monoxide,carbon dioxide,hydrogen and nitrogen 5aii) i)colloids is an intermediate between true solution and a suspension ii)condensation is the process by which water vapour in the air is changed to liquid water

5bi) CaC03+2HCl—–>CaCl2+H2O+CO2 5bii) i)it is used in fire extinguishers ii)it is used in the manufacturing of mineral water iii)carbon(iv)oxide is used as a coolant in nuclear reactors 5biii) i)Cr2O7^-2 =2Cr + C-2*7) = -2 2Cr – 14 = -2 2Cr = -2 + 14 2Cr/2 = 12/2 Cr = 6 ii)Cr2{SO4}3 2Cr + 3 (-2*1 + -2*4) = 0 2Cr + 3 (-2 – 8) = 0 2Cr + 3 (-10) = 0 2Cr – 30 = 0 2Cr/2 = 30/2 Cr = 15

5ci) vulcanization is a chemical process of converting netural rubber or related polymers into more durable materials through the addition of sulphur or other equivalent curatives or accelerators 5cii) Time Taken(t) for 6.35g of copper(ii)tetraoxosulphate solution Cu^2^+ + 2c ——->Cu Q = 2*63.5*95600 Q = 12255500 Q = 1t 12255500/10 = 10*t/10 t = 1225550/60 = 204258.3 5ciii) Latex ==================================

4ai) electrolytic cell is a cell that consist of a container of electrolyte with two electrodes connected to a suitable direct current supply 4aii) i)daniel cell ii)Leclanché cell 4aiii) i)copper ii)tin 4aiv) action of dilute acide on zinc 4av) Zn+2HCl——>ZnCl+H2

4bi) i)dinitrogen(i)oxide(N2O) ii)nitrogen(v)oxide(N2O5) iii)nitrogen(iv)oxide(NO2) 4bii) charle’s law states that the volume of a fixed mass of gas varies directly with the absolute(kelvin)temperature provided the pressure remains constant. 4biii) P1 V1 = P2 V2 given that P1 = 900mmHg P2 = 750mmHg V1 = 300cm^3 V2 = ? V2 = P1V1/P2 V2 = 900*300/750 V2 = 270000/750 V2 = 360cm^3 4biv) % composition carbon = 12/(12*6) + (1*6) *100% = 12/72+6 *100 = 12/78 * 100% = 1200/78% %composition of carbon = 15.38%

4c) TABULATE -THERMOPLASTS- i)it melts when heat is applied to it ii)highly recycled -THERMOSETS- i)does not melt when heat is applied ii)cannot be recycled ==================================

2ai) ionization energy deals with electron loss while electron loss while electron afinity deals with electron gain 2aii) i)they are used to dry gases ii)they are used to recover valuable vapours from industrial effluents and refine petroleum

2bi) TABULATE -RHOMBIC SULPHUR- i)bright yellow in colour ii)it is octohedral in shape -MONOCLINIC SULPHUR- i)amber in colour ii)it is needle like in shape 2bii) oxygen = 60% sodium = 40% oxygen 60/16 3.75/1.74 = 2 sodium 40/23 1.74/1.74 = 1 the emperical formula is NaO2 2biii) sodium(iv)oxide

2ci) i)x is hydrophobic region ii)y is hydrophilic religion 2cii) i)for laundry purpose ii)for fuel 2ciii) i)the distance of outermost electron from the nucleus ii)the size of the positive nuclear charge iii)the screening effect of inner electrons 2civ) period law states that the properties of the elements are a period function of their atomic number

2di) n—pentane—–>n—butane—–>2—methylbutane—2,2—dimethylpropane 2dii) i)glucose ii)galactose ================================== Completed. enjoy.