All 36 questions from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2018 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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The formula CH₃CH(Cl)CH(OH)CH₃ represents
Since the hydroxyl functional group is closer to the right end, the chain is named from the right; the correct name is 3-chlorobutan-2-ol.
A violet or deep red-brown colour observed when hydroxylamine hydrochloride and sodium hydroxide are added to an organic substance confirms the presence of a(n)
This is a test for esters (also known as alkanoates); the test is known as the hydroxamic acid test.
The main raw materials for making glass are
The main raw materials for making glass are sand, limestone and sodium trioxocarbonate (iv).
In an electrolytic set up to tin-plate a metal X,
For tin to be plated onto metal X, tin is made the anode (source of tin ions) while X is made the cathode (where tin deposits).
According to the kinetic theory, an increase in temperature causes the kinetic energy of particles to
According to the kinetic theory, an increase in temperature causes an increase in the kinetic energy of particles.
Which of these is a basic salt?
Mg(OH)NO₃ is a basic salt (contains a hydroxide group); NaHSO₄ is an acid salt while Na₂SO₄ and NaCl are normal salts.
Trioxonitrate (v) acid does not react with metals to give hydrogen because it
Trioxonitrate (V) acid (nitric acid) is a strongly oxidizing acid, so it does not react with metals in the normal way to liberate hydrogen gas.
An organic acid contains 40% carbon, 6.6% hydrogen and 53.33% oxygen. Determine its empirical formula
Moles: C=40/12=3.33, H=6.6/1=6.6, O=53.33/16=3.33. Ratio C:H:O = 3.33:6.6:3.33 = 1:2:1, giving empirical formula CH₂O.
Which of the following properties qualifies CO₂ as a fire extinguisher?
CO₂ is used as a fire extinguisher as it neither burns nor supports combustion.
Sulphur is extracted from its deposit by the
Sulphur is extracted from underground deposits via the Frasch process.
20cm³ of a gaseous hydrocarbon was mixed with 150cm³ of oxygen and exploded in a closed vessel at room temperature. After cooling, 110cm³ of gases remained. After absorption by concentrated sodium hydroxide solution, the volume left was 50cm³. The molecular formula of the hydrocarbon is
Volume of CO₂ = 110−50 = 60cm³. Total volume of oxygen used = 150−50 = 100cm³. Using ratios derived from the combustion equation and Avogadro's law: the formula works out to C₃H₆ (propene).
A measure of the degree of disorderliness in a chemical system is known as
Entropy is the measure of the degree of disorderliness of a system.
What are the products of the reaction between ethyl ethanoate and ammonia?
This reaction is known as ammonolysis. The products are the corresponding alkanol and amide: CH₃COOC₂H₅ + NH₃ → CH₃CONH₂ + C₂H₅OH.
Which of the following metals will dissolve in aqueous sodium hydroxide?
Aluminium is an amphoteric metal and can react with (dissolve in) aqueous sodium hydroxide.
Which of the following reagents can be used to differentiate alkanals from alkanones?
Fehling's reagent is suitable for distinguishing an alkanal from an alkanone, since the former (aldehyde) reduces Fehling's solution while the latter (ketone) does not.
Charring of sugar occurs when it is
Charring of sugar occurs when it is dehydrated, e.g. by adding concentrated sulphuric acid, which leaves behind carbon.
Which of the following is not obtained by polymerization?
Plastic, polythene and cellulose are all polymers; petrol is a mixture of hydrocarbons obtained from crude oil, not from polymerization.
Which of the following elements is common to bronze and soft solder?
Bronze is an alloy of copper and tin, while soft solder is an alloy of lead and tin; tin is the element common to both.
An alkanoic acid has molecular mass of 88. Its molecular formula is
The general formula of alkanoic acids is CₙH₂ₙ₊₁COOH. Solving 12n+2n+1+12+16+16+1=88 gives n=3, so the formula is C₃H₇COOH.
Producer gas is a mixture of
Producer gas is a mixture of carbon monoxide (CO) and nitrogen (N₂).
In the reaction between sodium hydroxide and sulphuric acid solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralise 10cm³ of 1.25 molar sulphuric acid?
H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O. Using CaVa/na = CbVb/nb: (1.25×10)/1 = (0.5×Vb)/2 → Vb = (1.25×10×2)/0.5 = 50cm³.
2.5g of potassium trioxonitrate (V) saturates 20g of water at 25°C. Calculate its solubility in grammes per 100g H₂O
Solubility = (2.5/20)×100 = 12.5g per 100g of water.
Calculate the mass of copper deposited when a current of 0.5 ampere was passed through a solution of copper (II) chloride for 45 minutes in an electrolytic cell [Cu=64, F=96500 Cmol⁻¹]
Charge Q = It = 0.5×(45×60) = 1350C. Moles of electrons = Q/F = 1350/96500. Cu²⁺+2e⁻→Cu, so moles Cu = ½×(1350/96500). Mass = moles×64 ≈ 0.224g.
Ca(OH)₂(aq) + 2NH₄Cl(aq) → CaCl₂(aq) + 2H₂O(l) + X. In the reaction above, X is
This is the standard reaction of ammonium salts with a base, releasing ammonia gas (NH₃) and water.
Temporary hardness of water is formed when rain water containing dissolved carbon (IV) oxide flows over deposit of
Rainwater containing dissolved CO₂ reacts with calcium (IV) oxide/carbonate (CaCO₃) deposits to form soluble calcium hydrogen carbonate, causing temporary hardness.
The salt formed from a weak acid and a strong base hydrolyzes in water to form a(n)
A salt of a weak acid and strong base hydrolyzes in water to form an alkaline solution.
The process that occurs when two equivalent forms of a compound are in equilibrium is
When two equivalent structural forms of a compound exist in equilibrium (interconvertible resonance structures), this is described as resonance.
Calculate the amount in moles of a gas which occupies 10.5dm³ at 6atm and 30°C. (R = 0.82 atm dm³K⁻¹mol⁻¹)
Using PV=nRT: n = PV/RT = (6×10.5)/(0.082×303) ≈ 63/24.85 ≈ 1.623 mol (using R≈0.082, T=303K).
¹³₇F + X → ²²₁₁Na + ⁴₂n. In the equation above, X is
Balancing mass and atomic numbers on both sides of the nuclear equation identifies X as a proton, ¹₁P.
In the diagram (electrolysis set-up), Y is a fused CaO/B
In the described electrolysis diagram, Y (the electrolyte in the second cell) is represented as NaOH.
In the diagram, X is
Based on the described experimental set-up in the diagram, X is identified as SO₂.
Mild oxidation of propan-1-ol will yield
Mild (partial) oxidation of a primary alcohol like propan-1-ol yields the corresponding aldehyde, propanal; further oxidation would yield propanoic acid.
Ethane is prepared industrially by
Ethane is obtained industrially through the cracking of larger hydrocarbon fractions from crude oil.
Butter is an example of an emulsion in which a
Butter is an emulsion in which liquid (water droplets) is dispersed in a solid medium (fat).
In the laboratory preparation of trioxonitrate (V) acid, the nitrogen (IV) oxide formed as a by-product is removed by
Bubbling air through the resulting acid solution helps to remove/oxidise the nitrogen (IV) oxide by-product formed during the preparation.
Sodium hydroxide can be used
Sodium hydroxide (as a strong base) is used industrially in the purification of bauxite ore (the Bayer process) during aluminium extraction.
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