Neco 2015 Chemistry Obj And Theory Answers

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NECO-CHEMISTRY- ANSWER
Chem-TypE A
1-10: AEDBAEABCD
11-20: AACCAAEAAE
21-30: AADDBBADAA
31-40: DABADDACAD
41-50: ADBCEED – BB
51-60: ADCDEDCDED
———————–
chem-Type D
1-10: CDAAAEABAE
11-20: DDCACDCCAA
21-30: EED – ADBCAE
31-40: DBADDCADAA
41-50: ACBDAADDCB
51-60: ECCDECBBCD
———————–
obj type c
1-10. BABDCDAADA
11-20.DDAEDDAEDC
21-30. CCEDADBBBB
31-40. ADCADDDEBB
41-50. CADCBABABC
51-60. BDECDDCCBA

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
================
(No1)
-Physical changes only change the appearance of
a substance, not its chemical composition.
-it’s process that does not cause a substance to
become a fundamentally different substance.
-It involves physical changes.
-Examples : dissolving sugar in water (sugar
molecules are dispersed within the water, but the
individual sugar molecules are unchanged.)
-Boiling water (water molecules are forced away
from each other when the liquid changes to vapor,
but the molecules are still water.
Chemical change xteristics
It’s a process that causes a substance to change
into a new substance with a new chemical
formula.
-it’s also a process involving the breaking or
making of interatomic bonds and the
transformation of a substance (or substances) into
another
-Chemical changes cause a substance to change
into an entirely substance with a new chemical
formula
-Chemical changes are also known as chemical
reactions. The “ingredients” of a reaction are
called reactants, and the end results are called
products.
Examples: iron rusting (iron oxide forms) and
bread rising (yeast converts carbohydrates into
carbon dioxide gase)
1ii)
GASES DENSER DAN AIR IS THROUGH
DOWNWARD DELIVERY
ii)LESS dense,upward delivery Gases insoluble
and less dense
-Collection by water
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 tabulate 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
=================
2bi)
Gay Lussac’s Law of Combining Volumes states
that when gases react, they do so in volumes
which bear a simpleratio to one another, and to the
volume of the product(s) formed if gaseous,
provided the temperature and pressure remain
constant.
—————————–
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->H2SO4
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 i8ncompletely 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
48i6.30=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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