All 50 questions from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2014 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
Beryllium and aluminium have similar properties because they are
A. positioned diagonally to each otherCorrect
B. are both metals
C. belong to the same group
D. belong to the same period
Explanation
The similarity in the properties of beryllium and aluminium is due to their diagonal positioning in the periodic table. The same can be said of carbon and phosphorous, boron and silicon.
If the difference in electronegativity of elements P and Q is 3.0, the bond that will be formed between them is A.
A. ionicCorrect
B. covalent
C. metallic
D. co-ordinate
Explanation
If the electronegativity difference between two combining atoms is large, the bond will be ionic or electrovalent. Small electronegativity difference makes for covalent bond.
Ca(HCO₃)₂ and Mg(HCO₃)₂ are the major substances that are responsible for
A. permanent hardness
B. temporary hardnessCorrect
C. softness
D. alkalinity
Explanation
Ca(HCO3)2 and Mg(HCO3)2 are the major substances that are responsible for temporary hardness, while CaSO4 and MgSO4 are those responsible for permanent hardness.
Mass of Pb(NO₃)₂ = 16.55g. Given Mass of H₂O = 100g, taking the density of water as 1gcm⁻³ (volume of water = 100cm³ = 0.1dm³), calculate the solubility of Pb(NO₃)₂.
A. 0.50moldm⁻³
B. 0.16.55
C. 0.5modm⁻³Correct
D. 16.55g
Explanation
Molar mass of Pb(NO3)2 = 331gmol⁻¹. Mole of Pb(NO3)2 = 16.55g/331gmol⁻¹ = 0.05mol. Solubility = Conc. = Mole/Volume(dm³) = 0.05mol/0.1dm³ = 0.5moldm⁻³.
Ethanoic acid, CH₃COOH, has a basicity of 1. CH₃COOH can also be said to be monobasic. But CH₃COOH has 4 hydrogen atoms per molecule; why does it not have a basicity of 4?
A. It is because only one of those hydrogen can be ionizedCorrect
B. It is a weak acid
C. It has only one carboxyl group
D. It reacts slowly with bases
Explanation
CH3COOH can also be said to be monobasic, but CH3COOH has 4 hydrogen atoms per molecule; why does it not have a basicity of 4? It is because only one of those hydrogen can be ionized.
Which of the following salts will turn litmus red?
A. Zinc chloride
B. Sodium tetrahydroxozincate (II)
C. Potassium hydrogen tetraoxosulphate (VI)Correct
D. Sodium hydrogen tetraoxosulphate (IV)
Explanation
A solution of potassium hydrogen tetraoxosulphate (vi) will turn blue litmus paper red. If one is to consider the origin of the salt, it is from a strong acid (H2SO4) and a strong base (KOH). This would have made it a neutral salt. However, the presence of excess H+ makes it acidic.
Calculate the quantity of electricity required to liberate 10g of copper from a copper compound.
A. 15196.5Correct
B. 32395.5
C. 30156.3
D. 60784.5
Explanation
Q = It = 2 × (60×60)s = 7200C. For 1mole of Cu(64g), 2F(193000C) of electricity will be required. Thus 72000C will produce (64g/193000C)×7200C = 2.39g... For 10g copper: [Cu=64, F=96500Cmol⁻¹], Q required = (10/64)×2×96500 ≈ 15196.5C.
In an equilibrium reaction, which of the following conditions indicates that maximum yield of the product will be obtained?
A. Equilibrium constant is less than zero
B. Equilibrium constant is very largeCorrect
C. Equilibrium constant is very small B is favoured
D. ΔH−TΔS=0, ΔH>TΔS
Explanation
A large value of the equilibrium constant indicates that the reaction lies more to the right, i.e. product formation is favoured. A small value of the equilibrium constant indicates that the backward reaction is favoured.
Cr₂O₇²⁻(aq) + H₂O(l) ⇌ 2CrO₄²⁻(aq) + 2H⁺. What happens to the reaction when the hydrogen ion concentration is increased?
A. The equilibrium position will shift to the leftCorrect
B. More of the products will be formed
C. The reaction will not proceed
D. The equilibrium position will shift to the right
Explanation
When the concentration of hydrogen ion is increased, the backward reaction is favoured so as to enable the consumption of the H+. This is in accordance with Le Chatelier's principle.
In the extraction of sodium from fused sodium chloride, the anode is made of
A. iron
B. platinum
C. graphiteCorrect
D. sodium
Explanation
In the electrolytic extraction of sodium from fused sodium chloride, the anode is made of graphite because sodium is formed at the anode... [C: Chlorine is formed at the anode. Sodium does not react with platinum].
A few drops of NaOH solution was added to an unknown salt forming a white precipitate which is insoluble in excess solution. The cation likely present is A.
A. Al³⁺Correct
B. Zn²⁺
C. Pb²⁺
D. Ca²⁺
Explanation
In the electrolytic extraction of aluminium from alumina, the cathode is iron, graphite is anode. When NaOH forms a white precipitate insoluble in excess base, presence of Al3+ is confirmed.
H H H H | | | | H-C-C-C-C-H | | | | H Cl Br H. The IUPAC nomenclature of the compound above is A. 2-chloro-3-bromobutanol.
A. 2-chloro-3-bromobutanol
B. 2-bromo-3-chlorobutanolCorrect
C. 3-chloro-2-bromobutanol
D. 3-chloro-2-bromobutanol
Explanation
The alkanol obtained from the production of soap is A. methanol B. propanol C. ethanol D. glycerol — the IUPAC name of the shown compound follows alphabetical order, so the name is 3-bromo-2-chloro-butan-1-ol.
Ethyne is passed through a hot tube containing organo-nickel catalyst product benzene: 2C₂H₂ → C₆H₆. Due to the unstable nature of ethyne, it is stored by
A. passing ethyne through a hot tube containing organo-nickel catalyst product benzene
B. dissolving in propanoneCorrect
C. adding water
D. cooling to low temperature
Explanation
Due to the unstable nature of ethyne, it is stored by dissolving in propanone.
Polystyrene is widely used as packaging materials for fragile objects during transportation because of its
A. high compressibilityCorrect
B. high lightness
C. low density
D. high density
Explanation
Polystyrene is widely used as packaging materials for fragile objects during transportation because of its high compressibility. Its high compressibility makes it a good shock absorber.
The process of converting linear alkanes to branched chain and cyclic hydrocarbons by heating in the presence of a catalyst to improve the quality of petrol is referred to as
A. blending
B. refining
C. cracking
D. reformingCorrect
Explanation
The process of converting linear alkanes to branched chain and cyclic hydrocarbons by heating in the presence of a catalyst to improve the quality of petrol is referred to as reforming.
Acids (both organic and inorganic) react with carbonates to liberate carbon(IV) oxide. Since CH₃COOH (ethanoic acid) is an acid, the same must be expected of it: 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂. What type of substance is CH₃COOH?
A. an organic acidCorrect
B. an inorganic acid
C. a base
D. a neutral salt
Explanation
CH3COOH (ethanoic acid) is an organic acid, and like inorganic acids, it reacts with carbonates to liberate carbon(IV) oxide.
