Waec Gce 2016 Chemistry Obj And Theory Answers – Nov/Dec Expo

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CHEMISTRY OBJ
1ADCAADAADA
11DDDBBDDDCC
21CBBACBADAD
31CACCBDDADB
41CDBCDBCCBA
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(1a)
(i) Synthetic polymers have more yield and more durable natural polymers
(ii) Synthetic polymers have more resistance to fungal and microbial attack
(1bi) HC = CH + 2HBr –>
H H
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H – C – C – H
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Br Br
(1bii) 1,2 -dibromoethene
(1c) Benzene is soluble in ethanol because benzene and water are not miscible, water is polar while benzene is non polar.
(1di)
Le Chatelier’s principle states that if a system in equilibrium is disturbed by changes in determining factors, such as temperature, pressure, and concentration of components, the system will tend to shift its equilibrium position so as to counteract the effect of the constraint.
(1dii)
(I) K2SO3 wil be oxidized
(II) Zn will be oxidized
(1e)
Dynamic equilibrium is a steady state reached when a reversible reaction occurs at the same rate in both directions and haphysicsnchanging ratio of productsand reactants.
(1f)
Diagram
(1g)
The reaction starts and stops immediately because the reactants are concentrated and concentration increase rate of reaction
(1hi)
Law of conservation of matter/ mass
Law of definite proportion
(1hii)
The principles states that when distributing electron into the energy level,electron enters the orbital with the lowest energy first before higher ones ie according to their energy level
(1i)
Ionization energy of 13Al is less than 12Mg because Mg tends to release or donate its valence electron less readily than Al and the nuclear attraction of the valence or Mg is greter than that of Al
(1j)
-Substitution reaction
-Addition reaction
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(2ai)
Vander waal’s force are weak intermolecular gases at room temperature.
(2aii)
-Electronegativity difference
-Ionization energy
(2aiii)
-Ionization energy
-Electron affinity
(2b)
C-F and C-O
C-N and C-H-O and C-N and C-F and C-O
(2ci)
-Be=1S^22S^2
4Mg=1S^22S^22P^63S^2
They both have the same number of electron in the outermost shell
(2cii)
Mg^2+->Na^+->Ne
The size of positive ion is less than that of the neutral atom
(2bii)
C-F>C-O>C-N>C-H(order of polarity).
(2ci)
4Be=1S^2 2S^2
12mg =1S^2 2S^2 2P^6 3S^2.
(2cii)
4Be and 12Mg have similar chemical properties because they belong to the same group in the periodic table. Both 4Be and 12Mg belongs to group II in the periodic table hence they have similar chemical properties.
(2di)
Transition element: Transition elements are those element with partially or incompletely filled d-orbital. Transition metal form coloured ion (or compound), they acts as catalyst,they have variable oxidation stat, they are paramagnetic, they form complex compound or coordination compound
(2dii)
Most transition metals have variable oxidation state because they undergo bonding with the electron in the ns and (n-I) d-orbital .e.g. most of the first series of transition metal from scandium to Zinc have variable oxidation state because they undergo bonding with electron in 4s and 3d- orbital.
(2diii)
(i) Metals are used in electroplating
(ii) Metals are used in making electronic cables and cooking utensils because they are good conductor of heat and electricity.
(2div)
It is used in electroplating and galvanizing to make electrical cable
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(3ai)
Crystallisation is a separation technique that is used to separate a solid that has dissolved in a liquid and made a solution. The solution is warmed in an open container, allowing the solvent to evaporate, leaving a saturated solution.
(3aii)
Evaporation is the process of a substance in a liquid state changing to a gaseous state due to an increase in temperature and/or pressure.
(3aiii)
Filtration is any of various mechanical,physics