All 49 questions from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2011 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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What is the concentration of a solution containing 2g of NaOH in 100cm³ of solution? [Na=23, O=16, H=1]
Mass = 2g. Volume = 100cm³ = 0.1dm³. Molar mass of NaOH = 40gmol⁻¹. Mole = 2/40 = 0.05mol. Concentration = 0.05mol/0.1dm³ = 0.50 mol dm⁻³.
Which of the following properties is NOT peculiar to matter?
The highest entropy is found in gases while solids have the lowest entropy. Random motion of particles increases from solids to gases, not the other way round, so option A is the false statement.
The principle of column chromatography is based on the ability of column constituents to
The principle of column chromatography is based on the ability of constituents to move at different speeds in the column.
[Diagram: PV vs Temperature graph with lines K, L, M, N] From the diagram above, an ideal gas can be represented by
For an ideal gas, the product PV is constant at all temperatures, represented by the horizontal line N on the graph.
Which of the following statements is correct about the periodic table?
Elements in the same period have the same number of electron shells, and the number of valence electrons increases progressively across the period.
The relative atomic mass of a naturally occurring lithium consisting of 90% Li and 10% Li is
R.A.M. = (Mass1x%1 + Mass2x%2)/100 = ((7x90)+(6x10))/100 = 6.9.
An isotope has atomic number of 15 and a mass number of 31. The number of protons it contains is
Atomic number = proton number = 15.
The molecular lattice of iodine is held together by
The molecular lattice of iodine is held together by Van der Waal's forces, the weakest of the intermolecular forces.
The arrangement of particles in crystal lattices can be studied using
The arrangement of particles in crystal lattices can be studied using X-rays. This is known as X-ray crystallography.
[Diagram: number of moles of solute vs temperature graph] From the diagram above, find the amount of solute deposited when 200cm³ of the solution is cooled from 55°C to 40°C.
From the graph, solubility at 55°C = 6 moldm⁻³ and at 40°C = 5 moldm⁻³. Mole present in 200cm³ at 55°C = (200/1000)x6 = 1.2 mole. Mole present at 40°C = (200/1000)x5 = 1.0 mole. Mole crystallized out = 1.2 - 1.0 = 0.2 mole.
The importance of sodium aluminate (III) in the treatment of water is to
The use of sodium aluminate (III) in water treatment is to cause coagulation of fine particles in water.
What type of bond exists between an element X with atomic number 12 and Y with atomic number 17?
X=12X (2,8,2); Y=17Y (2,8,7). To attain octet, X loses two electrons while Y gains an electron, so two atoms of Y combine with one atom of X. The bonding type involving transfer of electrons is electrovalent bond.
Hardness of water is mainly due to presence of
Ca(HCO3)2 and Mg(HCO3)2 are responsible for temporary hardness of water, while CaSO4 and MgSO4 are responsible for permanent hardness; calcium trioxocarbonate (IV), CaCO3, is the underlying compound mainly responsible for hardness.
A suitable solvent for iodine and naphthalene is
Carbon disulphide (CS2) is a suitable solvent for iodine and naphthalene.
Which of the following noble gases is commonly found in the atmosphere?
Argon is the most abundant noble gas in the atmosphere.
N2O4(g) ⇌ 2NO2(g); ΔH=+ve. In the reaction above, an increase in temperature will
Since the forward reaction is endothermic (ΔH=+ve), an increase in temperature will shift the equilibrium to the right and increase the value of the equilibrium constant.
CH3COOH(aq)+OH(aq) ⇌ CH3COO(aq)+H2O(l). In the reaction above, CH3COO(aq) is the
A Bronsted-Lowry acid donates a proton, while the base accepts a proton. A conjugate acid-base pair differ by a proton. CH3COOH and CH3COO constitute a conjugate acid-base pair, with CH3COO as the conjugate base.
How many cations will be produced from a solution of potassium tetraoxosulphate (VI)?
Potassium tetraoxosulphate (VI), K2SO4, having the formula with '2' does not mean it produces two different cations - it produces just one type of cation, the potassium ion (K+). It is only a double salt that can have two different cations.
Which of the following is NOT an alkali?
Ammonia (NH3) is not an alkali but an alkaline gas.
An effect of thermal pollution on water bodies is that the
The solubility of gases decreases as temperature increases. Thus, thermal pollution (raising water temperature) reduces the level of dissolved oxygen in water bodies.
Which of the following is a deliquescent compound?
CaCl2 is deliquescent. Na2CO3.10H2O is efflorescent, while CuO is hygroscopic.
A chemical reaction in which the hydration energy is greater than the lattice energy is referred to as
For an exothermic reaction, the lattice energy is greater than the hydration energy, while the reverse (hydration energy greater than lattice energy) is the case for an endothermic reaction.
The function of zinc electrode in a galvanic cell is that it
The function of the zinc electrode in a galvanic cell is that it produces electrons (it is oxidized, releasing electrons).
CH4(g)+Cl2(g)→CH3Cl(g)+HCl(g). The major factor that influences the rate of the reaction above is
This reaction is catalyzed by light, i.e. it is a photochemical reaction, so light is the major factor influencing its rate.
The condition required for corrosion to take place is the presence of
Moisture (water) and oxygen are the two requirements for corrosion to take place.
[Diagram: energy profile diagram with reactants → products, X labeled] In the diagram above, X is the
X denotes the difference between the energy content of the products and that of the reactants, i.e. the enthalpy change.
[Diagram: rate of reaction decreasing over reaction time] The diagram above best illustrates the effect of decrease in
The graph represents the effect of a decrease in the concentration of reactants on reaction rate. As the concentration of reactant decreases, the reaction rate decreases as well.
MnO4(aq)+Y+5Fe2+(aq)→Mn2+(aq)+5Fe3+(aq)+4H2O(l). In the equation above, Y is
The balanced equation for the redox reaction between MnO4 and Fe2+ is: MnO4+8H+5Fe2+ → Mn2++5Fe3++4H2O. Thus, Y = 8H+(aq).
Given that M is the mass of a substance deposited during electrolysis and Q is the quantity of electricity consumed, then Faraday's first law can be written as [E=Electrochemical equivalent]
Faraday's first law states that the mass deposited is directly proportional to the quantity of electricity: M=EQ, where E is the electrochemical equivalent.
The impurities formed during the laboratory preparation of chlorine gas are removed by
In the laboratory preparation of chlorine gas, hydrogen chloride gas is produced as an impurity. It is removed by passing the gas into water, since HCl is highly soluble in water.
The effect of the presence of impurities such as carbon and sulphur on iron is that they
Presence of impurities in iron lowers its melting point (and also increases the boiling point of a liquid it may be dissolved in, per the general effect of impurities).
A few drops of concentrated HNO3 is added to an unknown solution and boiled for a while. If this produces a brown solution, the cation present is likely to be
The unknown solution originally contains Fe2+, whose heating with HNO3 will oxidize it to Fe3+, which manifests as brown coloration.
The bleaching action of chlorine gas is effective due to the presence of
The bleaching action of chlorine gas is effective due to the presence of water: Cl2+H2O→HCl+HOCl, then HOCl + coloured material → HCl+[O]+bleached material.
In the laboratory preparation of oxygen, dried oxygen is usually collected over
Dried oxygen is usually collected over mercury in the laboratory.
The property of concentrated H2SO4 that makes it suitable for preparing HNO3 is its
The property of H2SO4 that makes it suitable for preparing HNO3 is its boiling point (high boiling point, low volatility) - it is common practice to prepare a more volatile acid from a less volatile one.
Bronze is preferred to copper in the making of medals because it has
Bronze is stronger and more corrosion resistant than copper, making it preferred for medals.
The constituent of baking powder that makes the dough to rise is
The constituent that makes dough rise is NaHCO3. The rising is due to CO2 gas filling the spaces within the flour, released upon decomposition: 2NaHCO3 → Na2CO3+H2O+CO2.
Which of the following compounds is used as a gaseous fuel?
Propane (CH3-CH2-CH3) is commonly used as a gaseous fuel; the cooking gas ('utilgas') used at home is propane or butane.
The ability of carbon to form long chains is referred to as
The ability of an element to form long chains using its own atoms is known as catenation.
Which of the following compounds will undergo polymerization reaction?
Polymerization is common to alkenes and alkynes. C2H4 (ethene) readily undergoes polymerization - important in the plastic industry.
[Structure: CH3-C(OH)(COOH)-H] The compound above exhibits
This compound will exhibit optical isomerism, since it possesses at least one carbon atom surrounded by four different atoms/groups.
An organic compound has an empirical formula CH2O and vapour density of 45. What is its molecular formula? [C=12,H=1,O=16]
Relative molecular mass = 2 x vapour density = 90. (CH2O)n = 90; (12+2+16)n = 90; 30n = 90; n = 3. Molecular formula = (CH2O)3 = C3H6O3.
C6H12O6 -zymase(25°C)→ 2C2H5OH+2CO2. The reaction represented by the equation above is useful in the production of
This reaction demonstrates fermentation, which is useful in the production of ethanol.
The number of isomers that can be obtained from C4H10 is
Butane, C4H10, has only two isomers: n-butane and 2-methylpropane (isobutane).
[Structure: H-C-C-C-C-Cl with H's and an OH shown] The functional groups present in the compound above are
The functional groups present are hydroxyl and chloro group (the term 'halo group' is ambiguous, so the more specific 'chloro-group' is correct).
Which of the following is a primary amine?
A primary amine has only one alkyl group attached to the nitrogen atom, e.g. CH3NH2. A secondary amine has two alkyl groups, e.g. (CH3)2NH, while a tertiary amine has three, e.g. (CH3)3N.
Two organic compounds K and L were treated with a few drops of Fehling's solution respectively. K formed a brick-red precipitate while L remains unaffected. The compound K is an
Fehling's solution distinguishes alkanals (aldehydes) from alkanones (ketones). Alkanals produce a red precipitate with Fehling's solution (they have an oxidizable hydrogen atom, R-CHO) while alkanones do not (R-CO-R).
Which of the following statements is true about 2-methylpropane and butane?
2-methylpropane and butane are isomers - they have the same molecular formula and chemical properties, but different physical properties such as boiling point.
CH3COOH + C2H5OH -Conc.H2SO4→ CH3COOC2H5 + H2O. The reaction above is best described as
This equation demonstrates esterification - the reaction between an alkanoic acid and an alkanol (in the presence of H+ catalyst) to produce an ester and water.
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