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Chemistry Neco 2015 Answers Available Now!!!




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Wednesday 17th June Paper III & II: Objective
& Essay –
Chemistry – 10:00am – 1:00pm


OBJ TYPE C
1B-The collision between the gas molecules
2A-1s^22s^22p^63s^23p^5
3B-negatively charged ion
4D-High pressures
5C-40
6D-I^-(aq)
7A-addition reaction
8A-can reach completion and by changing the conditions can go back to give the starting substances as products
9D-K^+
10A-calcium hydrogen trioxocarbonate(iv)is decomposed by heat
11D-Monoclinic
12D-Tetraoxosulphate(vi)acid
13A-chromatography
14E-separating funnel
15D-Have the same number of valence electrons
16D-The distance between the comparison
17A-acid
18E-SO4^2-
19D-2.24
20C-210.2
21C-oxidation
22C-benzophenol
23E-methyl propanoate
24D-zinc
25A-cooordiate covalent
26D-increase
27B-16.2
28B-beryllium and boron
29B-m proportional as It
30B-electrons
31A-hydrogen and chlorine
32D-(-15)
33C-oxidation power
34A-H2S
35D-oxidation number
36D-iron
37D-6
38E-thermal oxidation
39B-150
40B-boyle's
41C-nature reactants
42A-H2O(l)->H2O(s)
43D-hydrogenation
44C-C4H10
45B-calcium
46A-brass
47B-carbon
48A-K2CO3
49B-32
50C-lactic
51B-monobasic
52D-Trioxonitrate(V)
53E-(238)(92)U
54C-helium
55D-54
56D-lithosphere
57C-efflorescence
58C-2,3-dimethylhexane
59B-glucose
60A-fructose


Chem-Type A
1-10: AEDBAEABCD
11-20: AACCAAEAAE
21-30: AADDBBADAA
31-40: DABADDACAD
41-50: ADBCEED - BB
51-60: ADCDEDCDED

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CHEMISTRY OBJ obj type c
1-10. BABDCDAADA
11-20.DDAEDDAEDC
21-30. CCEDADBBBB
31-40. ADCADDDEBB
41-50. CADCBABABC
51-60. BDECDDCCBA

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chem-Type D
1-10: CDAAAEABAE
11-20: DDCACDCCAA
21-30: EED - ADBCAE
31-40: DBADDCADAA
41-50: ACBDAADDCB
51-60: ECCDECBBCD

1a. Physical change
i. It is easily reversible.
ii. No new substance are formed.
iii. There is no change in the mass of a substance involved in
such a change.
iv. It does not involve any great heat change except the heat
changes which occur during changes of state, e.g the heat of
dissolution and the latent heats of fusion and vaporization.
CHEMICAL CHANGE.
i. It is not easily reversible.
ii. Entirely new substances are always produced.
iii. there is a change in the mass of a substance that
undergoes such a change.
iv. A considerable amount of heat change is usually involved.
1ii)
GASES DENSER DAN AIR IS THROUGH
DOWNWARD DELIVERY
ii)LESS dense,upward delivery
Gases insoluble and less dense
-Collection by water
1bi) HCL gas and ammonia gas
1bii) highly soluble in water
1biii)
==> Compound:
I) Element are chemically combined
II) It is homogeneous
==> Mixture:
I) Are physically combined
II) It is heterogeneous
1ci) An isotope is a form of a chemical element
whose atomic nucleus contains a specific
number of neutron s, in addition to the
number of proton s that uniquely defines
the element.
The nuclei of most atom s
contain neutrons as well as protons. (An
exception is the common form of hydrogen,
whose nucleus consists of a lone proton.)
Every chemical element has more than one
isotope.
1cii)
=> Atomic Mass(x) | 35 , 37
=> R.abundance (f) | 75 + 25 = 100
=> Atomic by R.A(fx) | 2625 , 925
Total of (Fx) = 2625 + 925 = 3550
RAM = 3550/100
= 35.5
"Note: they are in tabular form
The sign (,) means Next line"
1ciii) Hudrogen gas , tetrachloromethane,methane
1civ)
I) High boiling point and Melting points
ii) Soluble in water & insoluble in organic solvent

(2ai)
Ionization energy

(2aii)
Atomic radius

(2aiii)
Ionization energy increases across the period because the number of electronic shell increases
Atomic radius iincreases because the number of increases

(2aiv)
-Diffusion
-Brownian motion
-Osmosis

(2bi)
Gay lussac's law of combining volume states that the volumes of gases which take part in a chemical reaction bear a simple ratio to one another and to the volume of the gases

(2bii)
Given; nN2=0.64
nCO2=0.5
nO2=0.375
PT=PN2+PCO2+PO2
Molar mass of N2=14*2=28
Molar mass of CO2=12+16*2=44
Molar mass of O2=16*2=32
PN2=(nN2/(nN2+nCO2+nO2))PT
PN2=(0.64/(0.64+0.5+0.375))*760
PN2=(0.64/1.515)*760
PN2=321'mmHg
PCO2=(0.5/1.515)*760
=251mmHg
PO2=(0.375/1.515)*760
=188mmHg
(2ci)
The basicity of an acid is the number of replaceable hydrogen ion in one molecule of an acid

(2cii)
Tetyraoxosulphate(vi)acis is corrosive because its concentrated form causes serious burnt

(2ciii)
Acid salts-KHCO3
Basic salt-Na2CO3

(2di)
Deliquescence substance is a substance when exposed to the atmosphere absorb water from the atmosphere and suddenly turn to solution

(2dii)
Calcium
3a)
Diamond
-Diamond is tetrahedral in nature
-Diamond is the hardest substance
Graphite -Graphite is a crystalline solid
-Graphite has a low melting point
3b)
-Limestone is used to produce the carbon
( iv ) oxide
-Ammonia is used as catalyst
3ci)
Heavy chemicals -> Dye
Fine chemicals -> H2SO 4
3cii )
I- The higher the surface area of
reactants, the higher the rate of
reaction . Reactants in powered form
reacts faster than solid form
II -Catalyst helps to speed up the rate of
chemical reaction
III -Temperature ; The higher the
temperature of reacting vessels ,the higher the
rate of reaction
3d)
-Because they have i 8 ncompletely filled
3d- orbital
-Because they exhibit co-ordinate bond
between molecules -Because they have
magnetic domain
3e)
-Natural gas; It is used for cooking
-Bitumen; It is used for candle wax

5ai)
-Evaporation
-Combustion
-Carbon cycle
5aii )
I- Cathode is the negative electrode
through which current enters . Anode is
the positive electrode through which current
leaves
II -Conductors are solids which allow the
passage of electricity . Electrolyrtes are
solutions which conduct electricity
III -Strong acid is the acid which ionizes
completely in water. Concentrated acid is the
acid which contains no water dilution
5bi)
Mass of copper( m )= MQ /nF
0. 16 =( 63. 5* Q) /( 2* 96500 )
Q=( 0 . 16* 2* 96500 ) /63. 5
Q=486 . 30 Q =I* t
48i 6. 30 =I* ( 15* 60)
I=486 . 30 /900
I=0 . 54A
5bii )
Burning : oxygen is not required for burning while
Rusting : oxygen is required
for rusting
5biii )
-By electrolysis
-By putrification of ores
5ci) Sulphur
5cii )
-Bauxite
-Cryolite
5ciii )
-It speeds up the rate of chemical reaction
-It is not used up in reaction





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