JAMB UTME - Chemistry - 1998
Question 1 Rapport
The line observed in the sample hydrogen spectrum are due to emission of?
Détails de la réponse
The line observed in the sample hydrogen spectrum are due to the emission of energy by electron transition. When an electron moves from a higher energy level to a lower energy level, it releases energy in the form of light. This light is observed as a spectral line in the hydrogen spectrum. The different lines in the spectrum correspond to different energy transitions between the electron levels in the hydrogen atom. Therefore, the correct option is "energy by electron transition". The other options are not correct as they do not explain the observed spectral lines in the hydrogen spectrum.
Question 2 Rapport
On cracking medicinal paraffin, a gas is evolved which gives a pop sound with a lighted splinter and an oily liquid which decolourizes bromine solution is also obtained. The products of the cracking are ?
Détails de la réponse
When medicinal paraffin is cracked, two products are obtained - a gas and an oily liquid. The gas produced gives a pop sound with a lighted splinter, indicating the presence of hydrogen gas. The oily liquid obtained decolorizes bromine solution, indicating the presence of an unsaturated compound that can react with bromine. Therefore, the products of the cracking of medicinal paraffin are hydrogen gas and an unsaturated hydrocarbon (alkene), which is produced by breaking some of the carbon-carbon bonds in the original paraffin molecule. Thus, the correct option is: hydrogen gas and alkene.
Question 3 Rapport
A gas that turns a filter paper previously soaked in lead ethanoate solution black is?
Détails de la réponse
The gas that turns a filter paper previously soaked in lead ethanoate solution black is hydrogen sulphide (H2S). When H2S is passed through lead ethanoate solution, it reacts with lead ions (Pb2+) in the solution to form black lead sulphide (PbS). This reaction causes the filter paper soaked in lead ethanoate solution to turn black. Therefore, the correct option is "hydrogen sulphide".
Question 4 Rapport
The property used in obtaining oxygen and nitrogen industrially from air is the?
Détails de la réponse
Question 5 Rapport
Which of the following is observed when a solution of iron (III) chloride is mixed with a solution of sodium hydroxide?
Détails de la réponse
When a solution of iron (III) chloride is mixed with a solution of sodium hydroxide, a brown precipitate is formed. This reaction is a classic example of a precipitation reaction, which is a type of chemical reaction where an insoluble solid (precipitate) forms upon mixing two solutions together. In this case, the brown precipitate is iron (III) hydroxide, which is insoluble in water. The reaction can be represented by the following equation: FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl.
Question 6 Rapport
How many structural isomers can be drawn for the non-cyclic alkanol with molecular formula C 4H10O?
Détails de la réponse
The molecular formula of the given non-cyclic alkanol is C4H10O. To find the number of structural isomers possible, we need to draw all the possible structures with the given molecular formula. There are three types of isomers possible: 1. Chain isomers: These isomers differ in the arrangement of the carbon chain. For C4H10O, there are two possible arrangements of the carbon chain, giving two chain isomers. 2. Positional isomers: These isomers differ in the position of the functional group (-OH) on the carbon chain. For C4H10O, there are two possible positions for the -OH group, giving two positional isomers. 3. Functional group isomers: These isomers have a different functional group. However, since we are given that the compound is an alkanol (an alcohol), there are no functional group isomers possible. Therefore, the total number of structural isomers possible for C4H10O is the sum of chain and positional isomers, which is 2 + 2 = 4. Hence, the answer is 4.
Question 7 Rapport
8.0 g of an element X react with an excess of copper (ll) tetraoxosulphate (lV) solution to deposit 21.3 g of copper. The correct equation for the reaction is?(Cu = 64).
Détails de la réponse
Question 8 Rapport
In the diagram above , the activation energy for the backward reaction is
Détails de la réponse
The activation energy for a reaction is defined as the minimum amount of energy required for the reactants to form products. In the given diagram, the forward reaction has an energy level of 15 kJ, while the reverse reaction has an energy level of 40 kJ. Since the activation energy is the minimum amount of energy required for the reverse reaction to occur, it is the difference between the energy levels of the products and the activation energy of the reverse reaction. Therefore, the activation energy for the backward reaction is 40 kJ - 15 kJ = 25 kJ. Therefore, the correct answer is +25 kJ.
Question 9 Rapport
In the experiment above, X could be a solution of
Détails de la réponse
In the experiment above, X could be a solution of "sodium trioxonitrate (lll) and ammonium chloride". This is because the experiment involves the preparation of ammonia gas. Ammonia gas is obtained from the reaction of ammonium chloride and an alkali metal trioxonitrate (V). Sodium trioxonitrate (V) is an alkali metal trioxonitrate (V) while sodium trioxonitrate (lll) does not exist. Therefore, the only option that has an alkali metal trioxonitrate (V) and ammonium chloride is "sodium trioxonitrate (lll) and ammonium chloride".
Question 10 Rapport
The diagram above represents an atom that can combine with chlorine to form
Question 11 Rapport
The addition of water to calcium oxide leads to?
Détails de la réponse
The addition of water to calcium oxide results in a chemical change. This chemical reaction is also known as slaking of lime. When water is added to calcium oxide (also known as quicklime), a highly exothermic reaction takes place, releasing a large amount of heat energy. This reaction forms calcium hydroxide (also known as slaked lime), which is a white powder that is sparingly soluble in water. The chemical equation for this reaction is: CaO + H2O → Ca(OH)2 + heat energy So, the correct answer is "a chemical change."
Question 12 Rapport
3CuO(s) + 2NH3(g) → 3Cu(s) + 3H2O(I) N2(g) (i).
2NH3(g) + 3Cl2(g) → 6HCl(g) + N2(g) (ii).
4NH3(g) + 3O2(g) → 6H2O(I) + 2N2(g) (iii).
The reactions represented by the equations above demonstrate the?
Détails de la réponse
Question 13 Rapport
Alloys are often used in preference to pure metals because?
Détails de la réponse
Alloys are often used in preference to pure metals because the metallic properties of alloys are improved. Pure metals may have certain limitations or properties that are not ideal for a particular use. By combining two or more metals, alloys can have improved strength, hardness, corrosion resistance, ductility, and other properties. Alloys can also be less expensive than pure metals, as they can be made from less costly metals combined with smaller amounts of more expensive metals to achieve the desired properties. Therefore, the correct option is "metallic properties are improved in alloys".
Question 14 Rapport
Which of the following electron configurations indicates an atom with the highest ionization energy?
Détails de la réponse
Question 15 Rapport
Mg2+(aq) + 2e->(aq) → Mg(s)E°(volts) = 2.370
Zn2+(aq) + 2e->(aq) → Zn(s)E°(volts) = -0.763
Cds2+(aq) + 2e->(aq) → Cd(s)E°(volts) = 0.403
Cu2+(aq) + 2e->(aq) → Cu(s)E°(volts) = 0.340
In the electrochemical series above, the strongest reducing agents is?
Détails de la réponse
Question 16 Rapport
If an element X of an atomic number Z and mass number Y is irradiated by an intense concentration of neutrons, the relevant nuclear equation is?
Détails de la réponse
Question 17 Rapport
A common characteristic shared by iron and aluminium is that both?
Détails de la réponse
Question 18 Rapport
30cm3 of hydrogen was collected over water at 27°C and 780 mm Hg. If the vapour pressure of water at the temperature of the experiment was 10 mm Hg, calculate the volume of the gas at 760 mm Hg and 7°C?
Détails de la réponse
Y1 = 30cm3 T1 = 27 + 273 = 300K and P1 = (780 - 10)mm Hg i.e the pressure minus the vapour pressure of water
P2 = 760mm Hg and T2 = 7 + 273 = 280K
From (P2V2) / (T2) = (P1V1) / (T1)
(770 x 30) / (300) = (760 x O2) / (280)
V2 = (770 x 30x 280) / (300 x 760)
V2 = 28.4 cm3
Question 19 Rapport
A solid begins to melt when?
Détails de la réponse
A solid begins to melt when the constituent particles acquire a greater kinetic energy. When heat is added to a solid, the temperature of the solid increases. As the temperature increases, the kinetic energy of the particles in the solid also increases. At a certain temperature, called the melting point, the kinetic energy of the particles overcomes the intermolecular forces holding the solid together, causing the solid to transition into a liquid state. Therefore, option A is the correct answer.
Question 20 Rapport
2X(g) + Y(g) ? Z(g): In the equation above, The rate of formation of Z is found to be independent of the concentration of Y and to quadruple when the concentration of X is doubled. The correct equation for the reaction is?
Détails de la réponse
The question presents a chemical equation involving two reactants (X and Y) and a product (Z). The rate of formation of Z is found to be independent of the concentration of Y and to quadruple when the concentration of X is doubled. The task is to choose the correct equation for the reaction. The correct answer is R = k (X)^2 (Y)^0, which is the. The rate equation shows that the rate of formation of Z is directly proportional to the concentration of X squared and does not depend on the concentration of Y. The rate constant k is specific to the reaction and its temperature. The exponent of Y is zero, indicating that the concentration of Y does not affect the rate of formation of Z. Option (a) R = k (X)(Y) is incorrect because the rate is independent of the concentration of Y. Option (c) R = K (X)^0 (Y)^2 is incorrect because the rate of formation of Z depends on the concentration of X, and the exponent of X should be 2. Option (d) R = K (X)^2 (Y)^0 is correct, but it has a typo, where the degree symbol should be superscripted.
Question 21 Rapport
If sulphur (IV) oxide and methane are released simultaneously at the opposite ends of a narrow tube, the rates of diffusion Rso2 and Rch4 will be in the ratio? (S = 32, O = 16, C = 12, H = 1)
Détails de la réponse
Question 22 Rapport
Terylene is synthesized from ethane- 1, 2-diol and benzene - 1, 4-dicarboxylic acid by?
Détails de la réponse
Terylene is synthesized from ethane-1,2-diol and benzene-1,4-dicarboxylic acid by a condensation reaction. In this type of reaction, two molecules combine to form a larger molecule, with the elimination of a smaller molecule as a byproduct. In the case of Terylene, the smaller molecule that is eliminated is water. Therefore, the correct answer is condensation reaction.
Question 23 Rapport
90.0g of MgCI2 was placed in 50.0cm3 of water to give a saturated solubility of the salt is 8.0 mol dm3 at the same temperature, what is the mass of the salt left undissolved at the given temperature?(Mg = 24, Cl = 35.5)
Détails de la réponse
The question is asking for the mass of MgCl2 left undissolved in water. We know that the solubility of the salt is 8.0 mol dm^3 at the given temperature, and we have 50.0 cm^3 of water. Therefore, the maximum amount of MgCl2 that can dissolve in the water is: 8.0 mol/dm^3 x 0.050 dm^3 = 0.40 mol The molar mass of MgCl2 is: 24.3 + (2 x 35.5) = 95.3 g/mol So, the mass of MgCl2 that can dissolve in the water is: 0.40 mol x 95.3 g/mol = 38.12 g Therefore, the mass of MgCl2 left undissolved is: 90.0 g - 38.12 g = 51.88 g, which can be rounded to 52.0 g. So the answer is: 52.0g
Question 24 Rapport
Potassium tetraoxomanganate (VII) is often added to impure water to?
Détails de la réponse
Question 25 Rapport
The oxide that remains unchanged when heated in hydrogen is?
Détails de la réponse
Question 26 Rapport
C3H8(g) + 502(g) → 4H2O + 3CO2(g). Form the equation above the volume of oxygen at s.t.p. required to burn 50cm3 of propane is?
Détails de la réponse
C3H8 + 502 → 4H2O + 3CO2.
From the equation above 1 dm3 of C3H8 require 5dm3 of O2 at s.t.p.
∴ 50cm3 of C3H8 require x = (50) / (1000) x 5 x 1
x = (250) / (1000)
x = 250cm
Question 27 Rapport
Soap lather is an example of a colloid in which a?
Détails de la réponse
Soap lather is an example of a colloid in which a gas is dispersed in liquid. Colloids are mixtures in which small particles of one substance are dispersed evenly throughout another substance. In the case of soap lather, small bubbles of gas (air) are dispersed throughout a liquid (soap solution), creating a foam-like substance.
Question 28 Rapport
A mixture of iron and sulphur can be separated by dissolving the mixture in?
Détails de la réponse
Question 29 Rapport
Which of the following is true concerning the properties of benzene and hexane?
Détails de la réponse
It is a reaction between a saturated compound and unsaturated, so both will involve the sharing of molecules or transfer of molecules, which is substitution reaction.
Question 30 Rapport
A given amount of gas occupies 10.0 dm3 at atm, and 273°C. The number of moles of the gas present is?
(Molar volume of a gas at s.t.p. = 22.4 dm3)
Détails de la réponse
Question 31 Rapport
An example of aromatic compound is?
Détails de la réponse
An example of an aromatic compound is C6H5OH. Aromatic compounds are organic compounds that contain a cyclic arrangement of atoms with alternating double bonds, called an aromatic ring. These compounds are characterized by their stability and distinctive odors. C6H5OH, also known as phenol, is a common aromatic compound used in the manufacture of plastics, resins, and pharmaceuticals.
Question 32 Rapport
Excess phosphorus was burnt in a gas jar and the residual gas passed successively over concentrated KOH solution and concentration H2SO4 before being collected in a flask. The gases collected are?
Détails de la réponse
Question 33 Rapport
One mole of hydrocarbon contains 6g of hydrogen. If the molecular weight is 54, the hydrocarbon is an?
Détails de la réponse
CxH6
? CxH6 = 54
12x + 6 = 54
12x = 54 - 6
12x = 48
x = (48)/(12)
x = 4
We have CxH6 butyne
A formular of alkyne
Question 34 Rapport
A solution containing chloride ions gives white precipitate with silver trioxonitrate(V) Solution. The precipitate will be insoluble in dilute?
Détails de la réponse
Question 35 Rapport
2Cl2(g) + 2H2O(g) 4HCl(g) + O2(g)
∆H° = +115KJ mol-1. In the above equilibrium reaction, a decrease in temperature will?
Détails de la réponse
Question 36 Rapport
The pH of a solution obtained by mixing 100cm3 of a 0.2M solution of NaOH is?
Détails de la réponse
Question 37 Rapport
The soil around a battery manufacturing factory is likely to contain a high concentration of?
Détails de la réponse
The correct answer is "Pb2+ salts". Battery manufacturing involves lead-acid batteries which contain lead compounds. Lead (Pb) is toxic, and it can easily contaminate the soil around the factory site through various processes such as leakage or disposal of waste materials. Once lead is in the soil, it can easily bind to the soil particles and remain there for a long time. Therefore, the soil around a battery manufacturing factory is likely to contain a high concentration of Pb2+ salts. Ca2+, Mg2+, and Al3+ salts are not typically associated with battery manufacturing and are less likely to be found in high concentrations in the soil around a battery manufacturing factory.
Question 38 Rapport
All the metal below will react with water only in the form of steam to liberate hydrogen gas EXCEPT?
Détails de la réponse
