Waec Gce 2016 Chemistry Obj And Theory Answers

CHEMISTRY OBJ
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11DDDBBDDDCC
21CBBACBADAD
31CACCBDDADB
41CDBCDBCCBA
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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
 
 1a)
i)they are relatively of low cost
ii)They have high heat resistance
1bi)
draw the structure
H H
H-C-C-H
Br Br bromoethane
1bii)
bromoethene
1c)
Because Ethanol is less denser than water

1di)
Le Châtelier’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

1dii)
i)F2+2NaOH—–>NaOF+NaF+H20
ii)Cl2+2NaOH—–>NaOCl+NaCl+H20

1dii)
i)K2SO3 has been oxidized
ii)Ag^2+ has been oxidized

1e)
dynamic equilibrium is a steady state reached when a reversible reaction occurs at the same rate in both directions and has an unchanging ratio of products and reactants.
1f)
diagrams
(k)** (k)** (2) (k)** (k)**

1g)
because it attains equilibrium at very fast rate
1hi)
i)electrovalent bonding.
ii)covalent bonding

1hii)
Aufbau principle states that hypothetically, electrons orbiting one or more atoms fill the lowest available energy levels before filling higher levels (e.g., 1s before 2s). In this way, the electrons of an atom, molecule, or ion harmonize into the most stable electron configuration possible.
1i)
The outer electron in aluminium is in a p sub-level. This is higher in energy than the outer electron in magnesium, which is in an s sub-level, so less energy is needed to remove it.
1j)
i)Substitution
ii)addition
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3ai)
  Crystallizationis 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, physical or biological operations that separate solids from fluids (liquids or gases) by adding a medium through which only the fluid can pass.

3bi)
i)Their Melting and Boiling Points increases down the group
ii)Their atomic Radius increases down the group
iii)Their Ionization Energy: decreases down the group

3bii)
4NaOH(aq)+2F2(aq)->4NaF(aq)+O2(g) +2H2O(l)
Cl2(g)+2NaOH(aq)->NaOCl(aq)+NaCl(aq)
+NaCl(aq)+H2O(l)

3ci)
Gas is a state of matter while vapour is
the gaseous state of substance in equilibrium with its liquid or solid state
3cii)
Normal temperature and pressure
3di)
Mg(s)+Cl2(g)->MgCl2(s)

3dii)
n=mass/molarmass
n=24/35.5
n=1.2/24
n=0.05
number of moles=volume used/molar
volume 0.05=V/22.4
V=1.12dm^3

3e)
-Atomic number is the number of protons present in an atomic nucleus of the element
-Mass number of an element is the sum of the protons and neutrons in the atomic nucleus of the element
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4ai)
Hard water is water which does not lather readily with soap. Hard water is formed when water percolates through deposits of limestone and chalk which are largely made up of calcium and magnesium carbonates.

4ii)
-Temporary hardness: Ca(HCO3)2
-Permanent hardness: Na2C03

4aiii)
-By using chemicals like caustiic soda.
-By using permutot OR zeolite

4bi)
i) coagulation
ii) sedimentation
iii) filtration
iv) chlorination/disinfection

4bii)
i) Sodium chloride
ii) Potassium chloride
iii) Chlorine dioxide



4ci)
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent.
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