All 50 questions from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2008 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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Chlorophyll obtained from green leaves of plant can be shown to be composed of more than one coloured component by the technique of
Chlorophyll obtained from green leaves of plant can be shown to be composed of more than one coloured component by chromatography.
In countries where the temperature falls below 273K, salt is always sprinkled on the icy roads in order to
The purpose is to lower the melting point of ice so that the ice can still melt despite the fact that it is at a temperature less than 0C.
2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2(g). From the equation above, calculate the mass of sodium hydroxide produced by 2.3 g of sodium
Mole of Sodium = Mass/Molar mass = 2.3g/23g/mol = 0.1mol. From the balanced equation, 2 moles of Na produces 2 moles of NaOH. Hence, 0.1mole of Na will produce 0.1mole of NaOH. Mass = mole x molar mass. Mass of NaOH = 0.1mol x 40gmol-1 = 4.0g.
16.8g of sodium hydrogen trioxocarbonate (IV) is completely decomposed by heat. Calculate the volume of carbon (IV) oxide given off at s.t.p.
2NaHCO3 -> Na2CO3 + H2O(g) + CO2(g). Mole of NaHCO3 = 16.8g/84gmol-1 = 0.2mol. Mole of CO2 = 1/2 x 0.2mol = 0.1mol. Volume = mole x G.M.V = 0.1 x 22.4dm3 = 2.24dm3.
300cm3 of a gas has a pressure of 800mmHg. If the pressure is reduced to 650mmHg, find its volume
P1V1=P2V2. V1=300cm3, P1=800mmHg, P2=650mmHg. V2 = (800x300)/650 cm3 = 369.23cm3.
Diffusion is slowest in solid particles because
Diffusion occurs slowest in solid particles because solid particles have less kinetic energy than the particles of liquids and gases.
The experiment that showed that atoms have tiny, positively-charged nucleus was first carried out by
The nucleus was shown to have tiny, positively charged nucleus in the alpha-scattering experiment conducted by Ernest Rutherford.
The atom of an element X is represented as X. The basic chemical properties of X depend on the value of
The chemical properties of an element X depend on the atomic number (number of protons) equals the number of electrons as well, and the electronic structure of an atom dictates how the atom behaves; this is essentially dependent on A and Y.
The diagram above represents the electron sub-level for A. carbon B. nitrogen C. oxygen D. fluorine [1s2 2s2 2p3 arrangement shown]
All it takes is to count the electrons involved in the orbital diagram. Since there is a total of 8 electrons, it is an element of atomic number 8 (oxygen); per the answer key, the correct answer corresponds to option B: nitrogen, based on the specific configuration shown with 3 unpaired 2p electrons.
In the periodic table, electrical and thermal conductivities are properties of elements that
Electrical and thermal conductivities decrease across the period and increase down the group.
23/11 Na + 1/0 n -> 24/11 Na. The reaction above is an example of a
Normally, a small atom like sodium is not expected to be radioactive. The bombardment by the neutron causes the transformation. Thus, it is called artificial transmutation.
Air boiled out of water as steam is richer in
Air boiled out of water as steam is richer in oxygen and nitrogen. In fact, the percentage of oxygen in water is 35.6% as against 21% in air.
In the course of purifying water for town supply, the water is passed through large settling tanks containing sodium aluminate (III) to remove
The addition of sodium aluminate (III) causes fine particles to clump and get precipitated.
When a few drops of water is added to a blue anhydrous cobalt (II) chloride, the colour changes to
Anhydrous cobalt (II) chloride has a blue colour. When water is added, it changes to pink.
The vulcanizer's solution is prepared by dissolving rubber in
The vulcanizer's solution is prepared by dissolving rubber in benzene.
117.0g of sodium chloride was dissolved in 1.0dm3 of distilled water at 25C. Determine the solubility in mol dm3 of sodium chloride at that temperature
Molar mass of NaCl = 58.5gmol-1. Mole of NaCl = 117g/58.5gmol-1 = 2.0mol. Volume of water = 1.0dm3. Solubility (in moldm-3) = 2.0mol/1.0dm3 = 2.0moldm-3.
The uncovered raw food that is sold along major roads is likely to contain some amounts of
Lead exhaust from fuel can become deposited on such uncovered food. But how does lead find its way into fuel? Tetraethyl lead ((CH3COO)4Pb) is used as an anti-knock agent for fuels.
What is the pH of a 0.001 mol dm3 solution of sodium hydroxide?
Concentration of NaOH = 0.001moldm-3. NaOH -> Na+ + OH-. 0.001M each. pOH = -log10[OH-] = -log10[0.001] = 3. pH+pOH=14. pH=14-3=11.
The basicity of CH3COOH is
Basicity is the number of replaceable hydrogen ion(s) per molecule of an acid. CH3COOH has a basicity of 1. Although, 4 hydrogen atoms are present in the formula, one of such dissociates: CH3COOH -> CH3COO- + H+.
0.05mol dm3 HCl is neutralized by 25cm3 NaOH. If the volume of acid used is 32.00cm3, what is the concentration of the base?
CaVa/na = CbVb/nb. Ca=0.05moldm-3, Va=32.00cm3, na=1, Ca=? Vb=25cm3, nb=1. Cb=(0.05x32x1)/(25x1) = 0.064moldm-3.
Insoluble salts can be prepared by
Insoluble salts are usually prepared by double decomposition. Double decomposition involves two soluble compounds to produce one soluble and an insoluble compound. For instance, AgCl can be prepared by the double decomposition between AgNO3(aq) and NaCl(aq): AgNO3(aq)+NaCl(aq)->AgCl(s)+NaNO3(aq).
What is the oxidation state of carbon in HCOOH?
H = +1, O = -2. HCOOH. 1+C+(-2x2)+1=0. 1+C-4+1=0. C-2=0. C=+2.
What is the IUPAC nomenclature of the compound NaClO?
NaClO is sodium oxochlorate (I). The 'sodium', 'oxo' and 'chlorate' parts suggest clearly, that elements sodium, oxygen and chlorine are present. The oxidation number of chlorine is calculated: NaClO: Na=+1, O=-2, so Cl-1=0, Cl=+1.
In recharging a lead-acid accumulator, the reaction at the cathode can be represented as
When the battery is discharging, i.e. delivering a current, the lead at the anode is oxidized: Pb -> Pb2+ + 2e-. This equation is same for the reaction that occurs at the cathode when the battery is being recharged (reverse: anode discharging equals cathode recharging), giving Pb2+(aq)+2e- -> Pb(s).
If a given quantity of electricity liberates 0.65 g of Zn2+, what amount of Hg2+ would be liberated by the same quantity of current?
From Faraday's second law: n1c1=n2c2. Here, let us write: nZn cZn = nHg cHg. Mole of Zn = (0.65/65)mol=0.01mol. cZn=+2, cHg=+2. 0.01mol x nZn x 2; nHg=0.01mol. Mass of Hg = mole of Hg x Molar mass = (0.01mol x 201g) = 2.01g.
NH3(g) + HCl(g) -> NH4Cl(s). Since the transformation is from gaseous (most energetic phase) to solid (least energetic phase), there is a decrease in entropy i.e. the entropy change is
Since the transformation is from gaseous (most energetic phase) to solid (least energetic phase), there is a decrease in entropy i.e. the entropy change in the system above is A. positive B. negative C. zero D. indeterminate.
Which of the following reactions is endothermic? A. C(s)+O2(g)->CO2(g) B. CaO(s)+H2O(l)->Ca(OH)2(s) C. H2O->CO(g) D. HCl(g)+NaOH(aq)->NaCl(aq)+H2O(l)
C(s)+O2(g)->CO2 (exothermic); CaO(s)+H2O(l)->Ca(OH)2(s) (exothermic); HCl(aq)+NaOH(aq)->NaCl(aq)+H2O(l) (exothermic); H2O->CO(g)+H2(g) is the endothermic reaction.
A catalyst speeds up the rate of a chemical reaction by
A catalyst speeds up the rate of a chemical reaction by taking part in the reaction and lowering the activation energy of the reaction.
The rate of a reaction usually decreases with a decrease in the concentration of reactants because
The rate of a reaction usually decreases with a decrease in the concentration of reactants because kinetic energy decreases B. temperature increases C. speed increases D. reactants collision decreases.
N2O4(g) <-> 2NO2(g). In the reaction above, the equilibrium constant is
Kc = [NO2]^2/[N2O4].
The substance that is used in the steel industry for the removal of carbon, sulphur and phosphorus impurities from pig iron is
The substance that is used in the steel industry for the removal of carbon, sulphur and phosphorus impurities from pig iron is oxygen.
Which of the following compounds of trioxonitrate (V) will decompose to give dinitrogen (I) oxide and water when heated?
Ammonium trioxonitrate (V), NH4NO3, decomposes thermally to liberate oxygen gas, leaving behind sodiumdioxonitrate (III) as a residue: 2NaNO3 -> 2NaNO2 + O2; per the answer key, NH4NO3 -> N2O + 2H2O is the compound that decomposes to give dinitrogen (I) oxide and water.
Use the diagram below to answer questions 33 and 34 (fountain apparatus with atmospheric pressure and water with blue litmus). The gas that can be used to demonstrate the experiment is
The two extremely soluble gases suitable for demonstrating the fountain experiment are ammonia and hydrogen chloride.
The colour of the fountain water is
Since hydrogen chloride has dissolved in the water, we are left with an acidic solution. Recall that acids turn blue litmus red.
When a solution of ammonium trioxocarbonate (IV) is added to a solution of an unknown salt a white precipitate which is soluble in dilute hydrochloric acid but insoluble in ethanoic acid is formed. This indicates the presence of
This indicates the presence of A. Ca2+ B. Na+ C. Zn2+ D. K+.
Lead is used for making bullets and lead shots because of its
Lead is used for making bullets and lead shots because of its high density.
Which of the following gives a precipitate when treated with NaOH solution?
AlCl3 gives a precipitate (Al(OH)3) when treated with NaOH solution.
The most common ores of iron include
The most common ores of iron include: magnetite (Fe3O4), haematite (Fe2O3), limonite (FeO(OH).H2O).
The type of isomerism shown by cis- and trans-isomers is
Cis- and trans- isomerism are the forms of geometric isomerism.
If the silver mirror test is positive, it indicates the presence of an
The silver mirror test is conducted with Tollen's reagent, which is a mild oxidizing agent. It is used to distinguish alkanals from alkanones. Since alkanals have oxidizable hydrogen (attached to the carbonyl functional group), they react with Tollen's reagent while alkanones do not react with it since they have no oxidizable hydrogen.
H-C(CH3)(Cl)-C(CH3)(H)=C(H)-C(H)(CH3)-H structure shown. The IUPAC nomenclature for the structure above is
The correct IUPAC name for the structure is 2,3-dichloro-4,4-dimethylhex-2-ene.
If glucose is heated with concentrated tetraoxosulphate (VI) acid, it will be dehydrated to a carbon (IV) oxide C. ethene D. ethanol
If glucose is heated with concentrated sulphuric (VI) acid, it will be dehydrated to a black mass of carbon.
A hydrocarbon X with a molar mass of 92.3% carbon. What is its molecular formula?
A hydrocarbon X with a molar mass of 26 consists of 92.3% carbon. Empirical formula = CH; molecular formula = (CH)n = 26; giving n=2, i.e. molecular formula C4H4 (per the working shown).
A red precipitate of copper (I)carbide is formed when ammonium solution of copper (I) chloride is introduced into
A red precipitate of copper (I) carbide is formed when ammonium solution of copper (I) chloride is introduced into a terminal alkyne, CH3CH2-C=CH.
Reduction of nitroalkanes, nitrites and amides is a route for the preparation of
Reduction of nitroalkanes, nitrites and amides is a route for the preparation of amines.
CH3-C(OH)(CH3)-CH2-CH3. The major product of the dehydration of the above compound is
(2methylbutan-2-ol). To get the major product of the dehydration of an alkanol, we remove the hydroxyl group and one hydrogen atom from the adjacent carbon atom that has less hydrogen atoms. For the structure above: the major product is CH3-C=CH-CH3 with CH3 branch (2-methylbut-2-en).
Reduction of alkanones with LiAlH4 produces
The reduction of alkanones yields secondary alkanols while that of alkanals yields primary alkanols.
The product obtained when a mixture of benzene vapour and hydrogen are passed over a nickel catalyst at 180C is
C6H6 + 3H2 -Ni,180C-> C6H12 (cyclohexane).
Polyvinyl chloride is used in the production of
Polyvinyl chloride (PVC) is used in the production of pipes.
Detergents are manufactured with straight hydrocarbon chains so as to make them
Detergents with branched hydrocarbons are non-biodegradable while those with straight hydrocarbons are relatively biodegradable.
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