Neco 2022 Chemistry questions and answers
Chemistry-Obj
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Chemistry-Essay-Answers
(1ai)
(i) KAl(SO₄)₂. 12H₂O
(ii) Na₂SO₄
(1aii)
Number of moles of sodium reascted = reacting mass/molar mass
= 3.6/23
= 0.1565moles
Number of moles of oxygen reacted = (1/4) x Number of sodium
= 1/4 x (3.6/23)
= 0.03913
Reacting mass of oxygen = Number of moles x molar mass
= 0.03913 x (16×2)
= 1.252grams
(1bi)
Air in gaseous form is first passed through caustic soda to remove CO₂. It is compressed and cooled until ut becomes a liquid at -200°C. It is then led to a fractionating column. On distillation, Nitrogen which has a lowet boiling point of -196°C is evolced first leaving behind Oxygen in liquid form. Further heating converts the liquid to a gas at -183°C.
(1bii)
(i) It is used for combustion
(ii) It is used for artificial respiration
(1biii)
This is because room temperature is warmer
(1biv)
(i) Methyl orange
(ii) Phenophthalein
(1ci)
An ion is an atom or molecule which has a net electric charge due to the loss or gain of one or more electrons.
(1cii)
HCl gas doesn’t contain ions
(1cii)
(i) Noble gases: Neon, Helium
(ii) Halogens: Iodine, Fluorine
(iii) Alkaline earth metals: Calcium, Magnesium
(1civ)
Halogens attain stable octet configuration by accepting an electron from donors Group I elements.
(1di)
A sol is a colloid where solid particles are dispersed in liquid medium.
(1dii)
Jelly
(1diii)
(i) Acid-base titrations are used to determine the percentage purity of a substance
(ii) Acid-base titrations are important to determine the number of water molecules in a hydrate.
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