CORRECT: 2017/2018 NABTEB GCE CHEMISTRY Questions And Answer Expo/Runs « on: November 29, 2017, 09:11:29 pm »  

NABTEB CHEMISTRY OBJ ANSWER
 1-10 BDCACCCBDD
 11-20 BCCCBADAAC
 21-30 CCDBADACBC
 31-40 CDDCAACCBD
 41-50 DBCADBACBA 

 1ai) The Aufbau principle originates from the Pauli’s exclusion principle which says that no two fermions (e.g., electrons) in an atom can have the same set of quantum numbers , hence they have to "pile up" or "build up" into higher energy levels.
 1aii) --An ionic bond involves the loose and gain of electrons ---A covalent bond involves the sharing of electron by two atoms where both atoms contribute ---A dative bond involves sharing of electrons but only one atom contribute the electrons to be shared
1bi) Periodic Law state that properties of the elements are a Periodic function of their atomic numbers
 1bii) --do/does not form common compound =K10 --liberate (s) hydrogen from cold water =J3 --are in the same group =J3,L13 --From(s) an ion by loss of three electrons=L13 1c i)Water - - >Non-linear shape ii) Ammonia-->trigonal pyramidal iii) Methane-->Tetrahedral iv)sulphur(iv)oxide-->Linear shape =========================

 (3ai) Allotropes are atoms of the same element in the same physical state but in different forms. (3aii) *TABULAR FORM* Diamond | Graphite Transparent. | Blank Very strong solid | Soft solid Octahedral shape | Hexagonal shape
 (3aii) Diamond -> For cutting glass For drilling limestones Graphite -> For making pencils For lubricating metals
 (3bi) An, electrolytic cell is made up of an electrolyte, electrodes and sources of electricity where the electrolyte decomposes.
 (3bii) 2 Faraday deposits 63.5g of copper i.e 2x96500c deposits 63.5g of copper 298,500c deposits Xg of copper X = 298,500x63.5 / 2x96500 =98.211g
 (3ci) A reducing agent is the substance that is oxides in a redox reaction
 (3cii) They will turn purple permanent to pink.
 (3ciii) - Pipeline product manufacturing company in portharcourt - Dangote cement in lokoja =========================

 (4ai) A saturated solution contains the maximum amount of solute that the solvent can take at a particular temperature.
 (4aii) A dilute solution contains more solution that solute contain at a temperature.
 (4aiii) A super saturated solution contains more than enough solute than the solvent can contain at the temperature.
(4b) Iodine - Chlorine - For killing micro organisms Alum - For coagulation
(4ci) It reacts with water to form acid It changes blue litmus paper to red It reacts with ammonia gas to form salt.
 (4cii) As an oxidising agent because it reduced to nitrogen gas. As an acidic oxide because the product formed are salt and water only.
 (4di) Disco sulphate
(iii) acid - Hso2
 (4dii) C2HSOH ------->CH3COOH+H20
 (4diii) C2HSOH -------> C2H4+H20 5a) Fractionating tower is the place where various fractions of crude oil are separated based on their boiling point
(5aii) i)Methane
 ii)ethane
 iii)Buthan
5aiii) H H | | H--H- C - - C=C-4 | | C | H -C-H | H 3-METHYL BUTYNE 5iv) i) C2H4(g)+H2] SO4(aq)--->C2H5HSO4 ii)C2H5HSO4+H2O-->C2H5OH(aq) +H2SO4(aq)
 5bi) The boiling point of the Alkanol is much higher even though the two compound are of similar relative molecular Mass. This is due to the presence of hydrogen bonds in butane. Although hydrogen bonds are not strong, much energy is still required to break them before the butan-1-ol molecules can escape as vapour
 5bii) When a wine bottle is uncorked, its contents are exposed to air , causing them to oxidize. ... Bacteria naturally present in grapes can turn either the sugars in grape juice or the alcohol in wine into acetic acid, giving it a vinegar taste (and eventually producing a wine vinegar).
 5biiii) i)it is used for making vinegar
 ii) it is used as a laboratory reagent
 iii)it is used for coagulation of rubber from latex and casein(protein) from milk
 5ci) Fat are solids usually of animal origin while Oils are liquid mainly from plants
 5cii) Oils can be changed into fat by hydrogenation. Margarine is made by this process. Oils, usually from plants such as oil palm, groundnut and soybeans oil, are heated to about 180°C in the presence of finely divided nickel and hydrogen is bubbled in at about 5atm.The hydrogen is added across the double bonds in the saturated carbon chains in the oil. The hardened oils are then mixed with salt, vitamins, skimmed and various fats to form margarine