Each question is followed by four options lettered A to D. Find the correct option for each question and shade in pencil on your answer sheet, the answer space which bears the same letter as the option you have chosen. Give only one answer to each question. An example is given below.
Which of the following elements reacts with water?
A. Carbon. B. Sodium. C. Sulphur. D. Iodine.
The correct answer is Sodium which is lettered D and therefore answer space D would be shaded.
Think carefully before you shade the answer spaces; erase completely any answer(s) you wish to change.
Do all rough work on this question paper.
Now answer the following questions.
1. Which of the following laws or theory cannot be explained by the application of the kinetic theory of gases?
Explanation:
The correct answer is:
D
Topic: Kinetic Theory of Gases
The kinetic theory of gases explains the behavior of gases and can be used to derive Boyle's, Charles', and Gay-Lussac's laws.
However, Dalton's atomic theory is a fundamental theory about the nature of matter and atoms, and it is not derived from or explained by the kinetic theory of gases.
2. The primary component of natural gas is
Explanation:
The correct answer is:
A
Topic: Composition of Natural Gas
Methane (CH4) makes up the majority of natural gas, typically comprising 70–90% of its content.
It is the simplest hydrocarbon and the main fuel used for heating and electricity generation in natural gas systems.
3. Thermal cracking of alkanes usually
Explanation:
The correct answer is:
B
Topic: Cracking of Hydrocarbons
Thermal cracking is a high-temperature process in which large alkane molecules decompose into smaller hydrocarbons, including alkanes and alkenes.
This decomposition reaction helps convert heavy fractions of crude oil into more useful lighter products like gasoline and ethene.
4. Carbon is deposited in the exhaust pipes of cars because of
Explanation:
The correct answer is:
C
Topic: Combustion of Hydrocarbons
Carbon deposits form in car exhausts when petrol undergoes incomplete combustion, typically due to insufficient oxygen. This results in the production of carbon (soot) instead of carbon dioxide, leading to black soot buildup in the exhaust system.
5. How many moles of copper would be deposited by passing 1 Faraday of electricity through a CuCl₂ solution?
Explanation:
The correct answer is:
B
Topic: Electrolysis and Faraday's Laws
In CuCl₂, copper exists as Cu2+. To deposit 1 mole of Cu from solution, 2 moles of electrons (2 Faradays) are needed. Therefore, 1 Faraday will deposit 0.5 moles of Cu.
6. Alkenes can be manufactured by
Explanation:
The correct answer is:
C
Topic: Organic Chemistry – Hydrocarbon Reactions
Alkenes are commonly produced through the cracking of large hydrocarbon molecules. This process breaks down long-chain alkanes into smaller alkanes and alkenes using heat and sometimes catalysts.
7. Petrochemistry is an example of
Explanation:
The correct answer is:
C
Topic: Branches of Chemistry
Petrochemistry deals with the transformation of crude oil and natural gas into useful products like plastics and fuels.
It is an example of applied chemistry because it involves practical industrial applications of chemical principles.
8. Species that occur in a reaction pathway but not in the overall reaction are known as
Explanation:
The correct answer is:
A
Topic: Reaction Mechanisms
Intermediates are species that appear in the steps of a reaction mechanism but cancel out when the steps are combined to give the overall reaction.
They are formed and consumed during the reaction process.
9. Which of the following statements is correct?
Explanation:
The correct answer is:
A
Topic: Isomerism and Hydrocarbon Properties
Pentane (C5H12) has three chain isomers: n-pentane, isopentane (methylbutane), and neopentane (dimethylpropane).
Including stereoisomers, it is often cited as having five isomers in total. Other statements are incorrect based on the nature of hydrocarbons and their reactions.
10. The best indicator to use for the titration of ethanoic acid with sodium hydroxide is
Explanation:
The correct answer is:
B
Topic: Acid-Base Titration
Phenolphthalein is the most suitable indicator for titrating a weak acid (ethanoic acid) against a strong base (sodium hydroxide), as it changes color in the basic pH range, accurately reflecting the endpoint of this type of titration.
11. The reduction half equation of the following reaction is:
Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
Explanation:
The correct answer is:
C
Topic: Redox Reactions
In the given reaction, copper ions (Cu2+) gain two electrons to form solid copper (Cu).
This is a reduction process. The correct reduction half-equation is: Cu2+(aq) + 2e− → Cu(s).
12. If 100 cm3 of a saturated solution of sodium tetraoxosulphate (VI) at 30 °C contains 10.5 g of the salt, what would be its solubility at this temperature?
13. An example of a crystalline substance that does not possess water of crystallization is
Explanation:
The correct answer is:
A
Topic: Water of Crystallization
Sodium trioxocarbonate (IV), commonly known as sodium carbonate, does not contain water of crystallization.
In contrast, other substances like iron(II) tetraoxosulphate and sodium tetraoxosulphate often possess water of crystallization.
14. The salt solution formed from a reaction between ethanoic acid and sodium hydroxide solution would be
Explanation:
The correct answer is:
B
Topic: Acid-Base Reactions
The reaction between ethanoic acid (a weak acid) and sodium hydroxide (a strong base) forms a salt, sodium acetate, which in solution is neutral.
The strong base neutralizes the weak acid, resulting in a solution with a near-neutral pH.
15. Which of the following reactions represents the hydrolysis of an alkanoate?
Explanation:
The correct answer is:
C
Topic: Hydrolysis of Alkanoates
The hydrolysis of an alkanoate (ester) involves breaking the ester bond in the presence of water, forming an alcohol and a carboxylate ion.
In the reaction CH3COOC2H5 + H2O → CH3COO− + CH3CH2OH, ethyl acetate (an ester) reacts with water to form acetate ions and ethanol.
16. Which of the following statements about the collision theory is correct?
Explanation:
The correct answer is:
D
Topic: Collision Theory
According to the collision theory, chemical reactions occur when particles collide with enough energy and proper orientation.
The rate of reaction depends on the number of these "effective collisions".
17. Why are H2SO4 and CaCl2not suitable for drying ammonia gas? They
Explanation:
The correct answer is:
A
Topic: Drying of Gases
H2SO4 and CaCl2 are not suitable for drying ammonia gas because they react with it, thus altering the composition of the gas instead of simply removing moisture.
18. Which of the following equations does not illustrate correctly one of the reactions of chlorine?
Explanation:
The correct answer is:
B
Topic: Reactions of Chlorine
Chlorine is less reactive than fluorine and cannot displace fluorine from its compounds.
Therefore, option B is incorrect, as Cl2 cannot react with NaF to produce F2.
19. How many unpaired electrons are present in 26Fe3+?
Explanation:
The correct answer is:A
Topic: Electronic Configuration and Unpaired Electrons
The atomic number of Fe is 26.
Its electronic configuration is [Ar] 3d6 4s2.
For Fe3+, three electrons are removed—two from the 4s orbital and one from the 3d orbital, leaving 3d5.
The five 3d orbitals each have one unpaired electron, so there are 5 unpaired electrons.
20. Going down group II in the periodic table normally
Explanation:
The correct answer is:D
Topic: Periodic Trends in Group II Elements
As you go down Group II of the periodic table, the atomic radius increases due to the addition of electron shells.
This increased distance from the nucleus and the greater shielding effect reduce the nucleus’s ability to attract electrons, leading to a decrease in electronegativity.
21. Which of the following elements has its valence electrons in the s-orbital?
Explanation:
The correct answer is:D
Topic: Electron Configuration
Sodium has the electron configuration 1s² 2s² 2p⁶ 3s¹. Its valence electron (in the outermost shell) is in the 3s-orbital, making it an s-block element.
The others (Aluminium, Phosphorus, Carbon) have their valence electrons in the p-orbitals.
22. The periodic property that is used to determine whether a covalent molecule is polar or not is
Explanation:
The correct answer is:B
Topic: Chemical Bonding – Molecular Polarity
Electronegativity is the ability of an atom to attract shared electrons in a chemical bond.
A difference in electronegativity between atoms leads to an unequal sharing of electrons, resulting in a polar covalent molecule.
23. The following steps are scientific methods except
Explanation:
The correct answer is:C
Topic: Scientific Methods
Open-mindedness is a personal trait or attitude of a scientist, not a step in the scientific method.
The main steps include observation, problem identification, hypothesis, experimentation, data collection, and analysis.
24. Isoelectronic species have the same number of
Explanation:
The correct answer is:D
Topic: Atomic Structure
Isoelectronic species are atoms or ions that have the same number of electrons.
For example, O2−, F−, Na+, and Ne all have 10 electrons and are therefore isoelectronic.
25. An element X has two isotopes, (⁶⁵₃₀X) and (⁶⁶₃₀X), with relative abundances of 60% and 40% respectively. The relative atomic mass of X is
Explanation:
The correct answer is:B
Topic: Isotopes and Relative Atomic Mass
The relative atomic mass is calculated by multiplying each isotope's mass by its relative abundance and summing the results:
26. The pairs of compounds that belong to the same homologous series is
Explanation:
The correct answer is:A
Topic: Homologous Series
C₂H₆ (ethane) and C₄H₁₀ (butane) are both alkanes and belong to the same homologous series, differing by CH₂ units.
Members of a homologous series have the same functional group and general formula.
27. A consequence of global warming is
Explanation:
The correct answer is:D
Topic: Climate Change
Global warming leads to melting of polar ice caps and rising sea levels, which increases the risk of flooding in low-lying coastal areas.
28. Which of the following gases has the lowest rate of diffusion?
[ H = 1.0, C = 12.0, N = 14.0, O = 16.0]
Explanation:
The correct answer is:B
Topic: Gas Laws (Graham's Law of Diffusion)
According to Graham’s Law, the rate of diffusion of a gas is inversely proportional to the square root of its molar mass.
Oxygen (O2) has a higher molar mass (32 g/mol) than nitrogen (28 g/mol), ammonia (17 g/mol), and methane (16 g/mol), thus it diffuses the slowest.
29. The gas that is less dense than air is:
Explanation:
The correct answer is:D
Topic: Properties of Gases
Nitrogen (N2) has a molar mass of 28 g/mol, which is slightly less than that of air (approximately 29 g/mol).
Therefore, nitrogen is less dense than air. Other options like carbon dioxide (44 g/mol), oxygen (32 g/mol), and chlorine (71 g/mol) are denser than air.
30. Which of the following equimolar solutions has the highest conductivity?
Explanation:
The correct answer is:A
Topic: Electrolytes and Conductivity
H2SO4 (sulfuric acid) is a strong diprotic acid that ionizes completely in solution, releasing more ions (2 H+ and SO42−) than the others.
This results in higher electrical conductivity compared to the weak acid H2CO3, the strong base NaOH (which provides fewer ions), and the salt CH3COONa.
31. What takes place at the cathode during electrolysis?
Explanation:
The correct answer is:D
Topic: Electrolysis
At the cathode, cations (positively charged ions) gain electrons (reduction) and are discharged as neutral atoms or molecules.
Anions (negatively charged ions) are attracted to the anode, where they lose electrons (oxidation).
32. How many grammes of NaOH(s) would be needed to produce 100.0 cm3 of a 0.20 mol dm-3 NaOH(aq)? [NaOH = 40.0]
Explanation:
The correct answer is:C
Topic: Molarity and Mass Calculation
To calculate the mass of NaOH needed, use the formula:
moles = concentration × volume
Convert the volume from cm3 to dm3 (100.0 cm3 = 0.100 dm3). Then, calculate the moles of NaOH:
moles = 0.20 mol/dm3 × 0.100 dm3 = 0.020 mol
Finally, calculate the mass:
mass = moles × molar mass = 0.020 mol × 40.0 g/mol = 0.80 g
33. The formation of a bond between hydrogen and a highly electronegative atom results in
Explanation:
The correct answer is:C
Topic: Chemical Bonding
When hydrogen bonds with a highly electronegative atom (like oxygen or nitrogen), it results in polarity.
This creates a dipole, where one end of the molecule has a partial positive charge and the other has a partial negative charge.
34. The molecule that has a non-polar covalent bond is
Explanation:
The correct answer is:A
Topic: Covalent Bonds
Cl2 (chlorine gas) has a non-polar covalent bond because both chlorine atoms have the same electronegativity, resulting in an equal sharing of electrons.
In contrast, HCl, NH3, and H2O all have polar covalent bonds due to differences in electronegativity between the atoms involved.
35. Which of the elements in the table below would react more readily with chlorine?
Element
Ionization energy (kJ mol-1 x 10-3)
W
12.0
X
21.0
Y
106.0
Z
200.0
Explanation:
The correct answer is:C
Topic: Reactivity with Chlorine
The reactivity of an element with chlorine generally increases as its ionization energy decreases.
The lower the ionization energy, the easier it is for the element to lose electrons and form a positive ion, making it more reactive with chlorine. Based on the table, W (12.0) and X (21.0) have the lowest ionization energies, and are therefore more likely to react with chlorine.
36. The relative molar mass of a gaseous hydrocarbon is 30. Determine its vapour density.
Explanation:
The correct answer is:
D
Topic: Vapour Density Calculation
To determine the vapour density, we use the formula:
Vapour Density = Molar Mass of the Gas / 2
Given the relative molar mass of the gas is 30, the vapour density is:
Vapour Density = 30 / 2 = 15
37. Consider the following reaction equation:
2SO3(g) → 2SO2(g) + O2(g); ∆H = +198 kJ mol-1
Which of the following statements about the reaction is correct?
Explanation:
Correct Answer: A
This is an endothermic reaction because ∆H is positive (+198 kJ mol-1), indicating that the system absorbs energy from the surroundings.
Therefore, 198 kJ of energy is absorbed during the reaction.
38. Which of the following properties does not give evidence of the kinetic theory of matter?
Explanation:
Correct Answer: D
Polymerization is a chemical reaction that involves the joining of small molecules (monomers) to form a larger molecule (polymer).
It is not a physical process that demonstrates the motion of particles, unlike melting, diffusion, and evaporation, which are key evidence of the kinetic theory of matter.
39. A compound that could be dried by using conc. tetraoxosulphate (VI) acid and not by calcium oxide is likely to be
Explanation:
Correct Answer: C
Concentrated tetraoxosulphate (VI) acid (H2SO4) is suitable for drying alkaline gases such as ammonia because it is acidic and can absorb water vapor without reacting significantly with the gas.
Calcium oxide, being basic, would react with alkaline gases and is therefore unsuitable.
40. Positive ions in a sea of electrons are found in
Explanation:
Correct Answer: B
Metallic bonds consist of positive metal ions arranged in a lattice, surrounded by a 'sea' of delocalized electrons.
This structure explains many of the characteristic properties of metals, such as electrical conductivity and malleability.
41. Dilute trioxonitrate (V) acid does not produce hydrogen when it reacts with metals because
Explanation:
Correct Answer: C
Dilute trioxonitrate (V) acid (HNO₃) does not typically liberate hydrogen gas when reacting with metals because it acts as a strong oxidizing agent.
Instead of producing hydrogen, it often reduces to nitrogen oxides.
42. How many moles are there in 3.0 g of O3?
[ O = 16.0 ]
Explanation:
Correct Answer: B
The molar mass of O3 is 3 × 16 = 48 g/mol. So, number of moles = mass / molar mass = 3.0 g / 48 g/mol = 0.0625 mol.
43. Copper (II) ions are able to participate in co-ordinate covalent bonding because they
Explanation:
Correct Answer: B
Copper(II) ions (Cu2+) can form coordinate covalent bonds because they have vacant d-orbitals that can accept lone pairs of electrons from donor atoms in ligands.
44. Determine the volume of 0.100 mol of HCl in 0.250 mol dm-3 of solution.
Explanation:
Correct Answer: A
We can use the formula: Concentration = moles/volume. Rearranging to find volume: Volume = moles / concentration = 0.100 mol / 0.250 mol/dm3 = 0.4 dm3 = 400 cm3.
45. Which of the statements about gases is not correct?
Explanation:
Correct Answer: C
According to the kinetic theory of gases, when gas molecules collide, they transfer energy, but the total kinetic energy of the gas system remains constant if the temperature is constant.
So, while individual collisions affect the kinetic energy of the particles involved, the total kinetic energy is not unchanged unless the temperature changes. Therefore, the statement "The total kinetic energy of the gas is not affected by collision" is incorrect.
46. Arrange the following compounds in decreasing order of their boiling points: NH3, HF, SiH4, CH4
Explanation:
Correct Answer: D
HF (Hydrogen fluoride) has the highest boiling point due to strong hydrogen bonding between molecules.
NH3 (Ammonia) also forms hydrogen bonds, but not as strong as HF, so it has the next highest boiling point.
SiH4 (Silane) and CH4 (Methane) have lower boiling points because they are nonpolar molecules and only exhibit weak London dispersion forces.
Therefore, the correct order of boiling points is HF > NH3 > SiH4 > CH4.
47. The following statements are correct except
Explanation:
Correct Answer: A
In general, the volume of solid metals does not decrease significantly when pressure is applied to them. Metals are relatively incompressible in their solid form.
In contrast, gases experience a large decrease in volume when pressure is applied.
The other statements are correct.
Carbon atoms in methane are indeed further apart than in solid diamond, particles move faster in gases than in liquids, and energy is released during freezing when a liquid turns to a solid.
48. The vapour density of an organic compound with the molecular formula C2H4O2 is
[ H = 1.0, C = 12.0, O = 16.0]
Explanation:
Correct Answer: B
Vapour density is calculated as half the relative molecular mass (RMM).
For C2H4O2:
RMM = (12 × 2) + (1 × 4) + (16 × 2)
= 24 + 4 + 32
= 60.
Vapour Density = 60 ÷ 2 = 30
49. A mixture containing two salts of different solubility can be separated by
Explanation:
Correct Answer: B
Crystallization is used to separate salts with different solubility by allowing the less soluble salt to crystallize out first upon cooling or evaporation of the solvent.
50. The separation technique that is suitable for separating iodine from tetrachloromethane is
Explanation:
Correct Answer: C
Solvent extraction is used when one of the substances (e.g., iodine) is more soluble in a second solvent (like water or alcohol) than in tetrachloromethane.
