Chemistry 2018 Jamb Examination
Chemistry 2018 Jamb Examination
Question 31
What is the concentration of a solution containing 2g of NaOH in 100cm³ of solution? [Na = 23, O = 16, H = 1]
Molar mass of NaOH = 23 + 16 + 1 = 40 g mol⁻¹.
Number of moles of NaOH = \( \dfrac{2}{40} = 0.05 \) mol.
Volume = 100 cm³ = 0.1 dm³.
Concentration = \( \dfrac{0.05}{0.1} = 0.5 \; \text{mol dm}^{-3} \).
Therefore, the concentration of the solution is 0.50 mol dm⁻³.
Number of moles of NaOH = \( \dfrac{2}{40} = 0.05 \) mol.
Volume = 100 cm³ = 0.1 dm³.
Concentration = \( \dfrac{0.05}{0.1} = 0.5 \; \text{mol dm}^{-3} \).
Therefore, the concentration of the solution is 0.50 mol dm⁻³.
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Question 32
How many atoms are present in 6.0g of magnesium? [Mg = 24, N.A = 6.02 × 10²³ mol⁻¹]
Number of moles of Mg = \( \dfrac{6}{24} = 0.25 \) mol.
Number of atoms = \( 0.25 \times 6.02 \times 10^{23} = 1.505 \times 10^{23} \).
Thus, approximately \( 1.51 \times 10^{23} \) atoms are present in 6.0g of magnesium.
Number of atoms = \( 0.25 \times 6.02 \times 10^{23} = 1.505 \times 10^{23} \).
Thus, approximately \( 1.51 \times 10^{23} \) atoms are present in 6.0g of magnesium.
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Question 33
The radioisotope used in industrial radiography for the rapid checking of faults in welds and casting is?
Cobalt-60 emits high-energy gamma rays, which can penetrate metals and reveal internal defects in welds and castings. This makes it suitable for industrial radiography.
Other isotopes like carbon-14 and iodine-131 are mainly used in biological and medical applications.
Other isotopes like carbon-14 and iodine-131 are mainly used in biological and medical applications.
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Question 34
Beryllium and aluminium have similar properties because they
Beryllium and aluminium exhibit a diagonal relationship in the periodic table, showing similar chemical properties such as amphoteric oxide formation and covalent bonding characteristics.
This similarity arises because they are diagonally related elements (Be in Group 2 and Al in Group 13).
This similarity arises because they are diagonally related elements (Be in Group 2 and Al in Group 13).
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Question 35
\( mE + nF \rightarrow pG + qH \)
In the equation shown, the equilibrium constant is given by?
In the equation shown, the equilibrium constant is given by?
For a general equilibrium reaction \( mE + nF \leftrightharpoons pG + qH \), the equilibrium constant \( K_c \) is given as:\[ K_c = \dfrac{[G]^p[H]^q}{[E]^m[F]^n} \]This expresses the ratio of the concentrations of products to reactants, each raised to their stoichiometric coefficients.
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Question 36
(I) 3CuO(s) + 2NH₃(g) → 3Cu(s) + 3H₂O(l) + N₂(g)
(II) 2NH₃(g) + 3Cl₂(g) → 6HCl(g) + N₂(g)
(III) 4NH₃(g) + 3O₂(g) → 6H₂O(l) + N₂(g)
The reactions represented by the equations above demonstrate the
(II) 2NH₃(g) + 3Cl₂(g) → 6HCl(g) + N₂(g)
(III) 4NH₃(g) + 3O₂(g) → 6H₂O(l) + N₂(g)
The reactions represented by the equations above demonstrate the
In these reactions, ammonia donates electrons and gets oxidised to nitrogen gas. This shows its reducing nature.
For example, in equation (I), CuO is reduced to Cu as NH₃ is oxidised to N₂.
Hence, the reactions demonstrate the reducing properties of ammonia.
For example, in equation (I), CuO is reduced to Cu as NH₃ is oxidised to N₂.
Hence, the reactions demonstrate the reducing properties of ammonia.
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Question 37
The salt that reacts with dilute hydrochloric acid to produce a pungent smelling gas which decolourises acidified purple potassium tetraoxomanganate(VII) solution is
Sodium sulphite (Na₂SO₃) reacts with dilute HCl to produce sulphur dioxide (SO₂), a pungent-smelling gas.
Na2SO3 + 2HCl → 2NaCl + H2O + SO2
SO₂ decolourises acidified KMnO₄ because it acts as a reducing agent, confirming the reaction involves Na₂SO₃.
Na2SO3 + 2HCl → 2NaCl + H2O + SO2
SO₂ decolourises acidified KMnO₄ because it acts as a reducing agent, confirming the reaction involves Na₂SO₃.
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Question 38
The refreshing and characteristic taste of soda water and other soft drinks is as a result of the presence of
The characteristic taste and fizz of soda water come from dissolved carbon(IV) oxide (CO₂).
When the bottle is opened, CO₂ escapes, producing effervescence and a tangy taste due to weak carbonic acid formation.
When the bottle is opened, CO₂ escapes, producing effervescence and a tangy taste due to weak carbonic acid formation.
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Question 39
Which of the following are mixtures?
I. Petroleum
II. Rubber latex
III. Vulcanizer’s solution
IV. Carbon sulphide
I. Petroleum
II. Rubber latex
III. Vulcanizer’s solution
IV. Carbon sulphide
Petroleum, rubber latex, and vulcaniser’s solution are all mixtures because they contain two or more substances physically combined in varying proportions.
Carbon disulphide (carbon sulphide) is a pure compound, not a mixture.
Thus, I, II, and III are mixtures.
Carbon disulphide (carbon sulphide) is a pure compound, not a mixture.
Thus, I, II, and III are mixtures.
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Question 40
A balanced chemical equation obeys the law of
A balanced chemical equation shows equal numbers of each atom on both sides, satisfying the law of conservation of mass.
This law states that matter is neither created nor destroyed in a chemical reaction; atoms are only rearranged.
This law states that matter is neither created nor destroyed in a chemical reaction; atoms are only rearranged.
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