2017 Neco Runz : Sure NECO Answers For Chemistry Obj & Theory 2017 / Expo

                           

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  :VERIFIED CHEMISTRY OBJ:

1-10:BCBAEDCCAB
11-20:CCACDEADBC
21-30:ECBDDADADC
31-40:CABEBBABCA
41-50:BBEBAABDEB
51-60:CBEEECEBDA
 NO1 SOLUTION

1ai)
i)neutral to Litmus paper
ii)Has a boiling point of 100°C

1aii)
=[Na] / [Na2So4]  × 100%
=23/ (23×2) +32+ (16×4)  × 100%
=23/142 × 100%
=16.2%
Percentage of mass of a sodium
=16.2%
Also,
[O4] /[Na2SO4]  × 100%
=(4×16) / 142 × 100%
=64/142 × 100%
=45.1%
Percentage of mass of oxygen
=45.1

1aiii)
-Aluminum
1iv)
-Bauxite (Al2O3 +2H2O)

1bi)
I = (A) Is2 , 2s2 ,2p2
II= (B) Is2 , 2s2, 2p6,3s2
III=(C) Is2, 2s2, 2p6
IV=(D) Is2 ,2s2, 2p6, 3s2,3p5
V=(E)  Is2, 2s2, 2p4

1bi)
A Standard solution is a solution of known concentration.it is a solution containing known amount (in grams or mols) of a substance in a known volume of a solution.

1bii)
A concentrated solution contains lesser molecule of water than a dilute solution

1Ci)
i)simple sugar
ii) complex sugar

1cii) diagram(coming as image)

1ciii)
Insert a glowing splinter into a test tube containing the unknown gas the rekindling of the glowing splinter indicates the presence of oxygen                      


NO2 SOLUTION

2ai)
i)Oxidation is a process involving on loss of electrons
ii)Reduction is a process involving the removal at electronegative elements as well as the addition of electro positive elements

2aii)
i)Nitrogen is a colourless,odourless and tasteless gas
ii)it is slightly lighter than air

2aiii)
X represents urea [(NH2)2Co)]
Y represents water[H2o]

2bi)
Chlorine|35|17|18|1s^2 2s^2 2p^6 3s^2 3p^5
Fluorine|18|9|10|1s^2 2s^2 2p^5

2bii)
No of moles= Mass/Molar mass
=5/25+16+1
=5/40
No of moles=0.125mole

2biii)
Relative atomic Mass=
(18 × 1/3) + (20 × 2/3)
=19.3

2ci)Faraday's second law of electrolysis states that, when the same quantity of electricity is passed through several electrolytes, the mass of the substances deposited are proportional to their respective chemical equivalent or equivalent weight.

2cii)
Single line represents the electrode/electrolyte reaction
- Double lines represents interface in the full cell

2ciii)
Polymerization is the process whereby two or more monomers link together to form a compound of high molecular mass called the polymer

2civ)
i)It is used as a fuel in rockets
ii)It is sometimes uses as an anti-freeze
iii)it is used to dissolve soaps,perfumes etc


NO3 SOLUTION

3ai)
i)high melting and boiling point
ii)Good conductors of heat and electricity
iii)Have characteristic lustre

3aii)
Zn,  Ca,  Au,  Pb
==========>
Increase

3aiii)
Strong electrolytes ionize completely but weak electrolytes only partially ionizes.

3bi)
Ethene is prepared from ethanol in two stage

1st stage==>heat ethanol with excess Conc H2SO4 acid at 170°C
C2H5OH(aq)  + H2SO4 ==>C2H5HSO4(aq) + H2O(l)

2nd stage==>Heat the resulting ethyl hydrogentetraoxo-sulphate(iv)
C2H5HSO4(aq) ==>C2H4(g) +H2SO4(aq)

The Ethene produce is passed through Conc NaOH to remove impurities

3ci)
i)Mechinery should be improved so that more efficient fuel combustion occurs
ii)People should be educated to make them aware of the causes and dangers of pollution

3cii)
Efflorescent substance loses water to the surrounding with deliquescent substance absorbs and turn into solution

3ciii)
i)It is used for absorbing carbon(iv) oxide in the laboratory
ii)It is used in making soap
iii)it is used in refining petroleum



O4 SOLUTION

4ai)
i)addition of soda
ii)addition of zeolite

4aii)
the solubility of KCl increase at a constant rate with the rise in temperature while the solubility of NaCl is independent of temperature

4aiii)
PH of a solution is measure of the molar concentration of hydrogen ions in the solution

4aiv)

i)A is most acidic
ii)E is most basic
iii)C is neutral


4bi)
i)gases are made up of molecules which are in constant random motion
ii)the particles do not attract each other
iii)during motion the molecules of the gas collides with one another and with the wallss of container

4bii)
given that
P 1 = 320MMHg
P 2 = 760MMHg
V 1 = 220Cm ^ 3
V 2 =?
T 1 = 22°C
T 2 = 100°C
using P 1V 1/ T 1= P 2V 2/ T 2
V 2 = 320 × 220 × 100 / 22 × 760
V 2 = 7040000 / 16720
V 2 = 421. 05cm ^ 3

4ci )
Daigram(coming as image)

4cii)
i)it is used for respiration
ii)it is used in industries for removal of carbon sulphur and impurities in pig iron
iii)oxygen is used as propelants in space rocket .                      



NO6 SOLUTION

6ai)
i)solution A is starch solution, sample B is Iodine
ii)the colouration is formed due to the formation of an Iodine starch complex
6iii)
i)Iodine is used in treatment of goitre
ii)Iodine is used in making dye for colour photography

6aii)
dalton's law of partial pressure states that in a mixture of non-reacting gases, the total pressureexerted is equal to the sum of the partial pressuresof the individual gases.

6bi)
C - 4.08/12, H - 0.68/1, O - 5.46/16
0.34/0.34, 0.68/034, 0.34/0.34
1, 2, 1.
The emperical formula is CH2O

6bii)
( CH2O)n =60
((12×1)+(1×2)+(16×1))n=60
(12+2+16)n=60
30n/30=60/30
n=2
(CH2O)2=C2H4O2
the molecular formular is C2H202

6ci)
i)exothermic reaction
ii)A is activation energy, B is DH(Negative)

6cii)
i)removeal of carbon(iv)oxide
ii)liquetying the air

6ciii)
vander waal forces

6di)
fats have higher melting point than oil because fats are more denser

6dii)
i)it is poisonous
ii)it is 2,5 times denser than air
iii)it is greenish-yellow gas with a choking smell

6diii)
Zn^2+ has comppletely filled d-orbitals and there are no vacant d-orbitals for the transition of electrons while Sc^3+ has completely empty d-orbital and there are no electrons for d-d transition thus they are colourless                      


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