Neco 2016 CHEMISTRY Obj And Theory Answers – May/July Expo - 24reporters©

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CHEMISTRY OBJ:
1-10DCBBCBBEDC
11CADECEBBDC
21EEBABDADBE
31AECCACDDDC
41DABABCBBCA
51CBBAABCADE

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

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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

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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

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