Subject: Chemistry Duration: 1hr 30 mins
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Table of Contents: Weekly Scheme of Work
- Week 1: Water: Sources, Types, Uses, and Structure; Lab Preparation and Test for Water
- Week 2: Hardness of Water: Causes, Removal, and Municipal Water Purification
- Week 3: Solubility and Solutions: Definitions, Solubility Curves, and Uses
- Week 4: Mass/Volume Relationship; Mole and Molar Quantities
- Week 5: Relative Atomic Mass and Molecular Mass; Mass and Volume Calculations
- Week 6: Acids and Bases: Standard Solution Preparation, Indicators, and Titration
- Week 7: Hydrocarbons: Nature of Carbon, Organic Compound Features, and Classification
- Week 8: Alkanes: Nomenclature, Preparation, Properties, and Uses
- Week 9: Alkenes: Nomenclature, Preparation, Properties, and Uses
- Week 10: Alkynes: Nomenclature, Preparation, Properties, and Uses
- Week 11: Aromatic Hydrocarbons: Benzene Structure, Preparation, Properties, and Uses
- Week 12: Alkanols: Types, Classes, Fermentation, Properties, and Uses
Section A: Objective Questions
- Water is described as a universal solvent because:
A. it dissolves only salts
B. it dissolves all liquids
C. it dissolves many substances
D. it is used for bathing - Hard water contains:
A. sodium ions
B. calcium and magnesium ions
C. chlorine gas
D. hydrogen gas - Temporary hardness in water can be removed by:
A. boiling
B. filtration
C. addition of salt
D. decantation - The chemical test for water is the use of:
A. blue litmus paper
B. cobalt (II) chloride paper
C. pH paper
D. red litmus paper - The structure of water is:
A. linear
B. circular
C. angular (bent)
D. tetrahedral - One method of purifying water for municipal supply is:
A. freezing
B. ionization
C. distillation
D. chlorination - Solubility is defined as:
A. mass of solute dissolved in 1g of solvent
B. mass of solvent dissolved in 100g of solute
C. maximum amount of solute that dissolves in 100g of solvent at a given temperature
D. minimum amount of solvent that dissolves a solute - Which of the following affects solubility?
A. pH
B. light
C. temperature
D. density - A solubility curve is a graph of:
A. volume vs mass
B. solubility vs temperature
C. solubility vs density
D. pressure vs solubility - What is the molar mass of H2O?
A. 16 g/mol
B. 18 g/mol
C. 20 g/mol
D. 12 g/mol - The mole is:
A. a measurement of volume
B. a measure of energy
C. the amount of substance containing as many particles as atoms in 12g of carbon-12
D. the mass of any element - What is the volume occupied by 1 mole of any gas at s.t.p?
A. 22.4 cm³
B. 22.4 dm³
C. 1.0 dm³
D. 44.8 cm³ - Which of the following is a strong acid?
A. HCl
B. CH3COOH
C. NH3
D. NaOH - What is the correct color change of methyl orange in acid?
A. Yellow to red
B. Red to yellow
C. Blue to red
D. Green to yellow - A standard solution is:
A. any solution of a known base
B. a solution of unknown concentration
C. a solution whose concentration is known
D. a mixture of acids - In a titration, the end point is determined by:
A. the bubbling of gas
B. colour change of the indicator
C. evaporation of solution
D. precipitation formation - Carbon is tetravalent because it:
A. forms 3 bonds
B. forms 4 covalent bonds
C. is unreactive
D. dissolves in acid - Organic compounds are mainly based on:
A. nitrogen
B. carbon
C. oxygen
D. sodium - Hydrocarbons are compounds of:
A. hydrogen and chlorine
B. hydrogen and carbon
C. oxygen and nitrogen
D. hydrogen and oxygen - Alkanes are:
A. unsaturated hydrocarbons
B. saturated hydrocarbons
C. aromatic compounds
D. alcohols - The general formula of alkanes is:
A. CnH2n
B. CnH2n+1
C. CnH2n+2
D. CnHn - Which of the following is an alkane?
A. C2H4
B. C3H8
C. C4H6
D. C6H6 - Alkenes are identified by which functional group?
A. -OH
B. -COOH
C. C=C
D. C≡C - Ethene is an example of a(n):
A. alkane
B. alkyne
C. alkene
D. aromatic - Alkyne functional group is:
A. C=C
B. -OH
C. C≡C
D. CH3 - The general formula for alkynes is:
A. CnH2n
B. CnH2n-2
C. CnH2n+2
D. CnH2n+4 - Which hydrocarbon is aromatic?
A. Ethyne
B. Ethane
C. Benzene
D. Methane - The molecular formula of benzene is:
A. C6H6
B. C6H12
C. C5H10
D. C3H6 - Benzene is best described as:
A. saturated hydrocarbon
B. unsaturated hydrocarbon with alternating double bonds
C. compound with triple bonds
D. alcohol - Alkanols contain which functional group?
A. -COOH
B. -OH
C. -CHO
D. -C=O - Ethanol is prepared industrially by:
A. photosynthesis
B. fermentation
C. combustion
D. hydrogenation - The boiling point of ethanol is approximately:
A. 100°C
B. 78°C
C. 60°C
D. 120°C - Which of the following is a property of ethanol?
A. It is solid at room temperature
B. It is non-flammable
C. It is a good solvent
D. It does not mix with water - Alcohols are classified based on:
A. their colour
B. the number of OH groups
C. the number of carbon atoms
D. their molar masses - Which of the following is a primary alcohol?
A. Ethanol
B. Propan-2-ol
C. Butan-2-ol
D. Methanal - The molecular formula of ethanol is:
A. C2H5OH
B. CH3COOH
C. CH3OH
D. C3H7OH - One use of ethanol is:
A. to solidify glass
B. as a cooling agent
C. in perfumes and as fuel
D. to rust iron - Which indicator is used in acid-base titration?
A. Phenolphthalein
B. Barium chloride
C. Sodium hydroxide
D. Iron sulphate - The relative molecular mass of CO2 is:
A. 40
B. 44
C. 32
D. 28 - What volume does 2 moles of gas occupy at s.t.p?
A. 22.4 dm³
B. 44.8 dm³
C. 11.2 dm³
D. 1.0 dm³
Section B: Theory
1. Water: Sources and Structure
(a) List two natural sources of water.
(b) Explain why water is referred to as a universal solvent.
(c) Describe the molecular structure of water.
2. Hardness and Purification of Water
(a) Differentiate between temporary and permanent hardness of water.
(b) State one method of removing each type of hardness.
(c) Outline three steps in the purification of water for municipal supply.
3. Solubility and Solutions
(a) Define solubility.
(b) State two factors that affect solubility.
(c) A solution contains 25g of a solute in 100g of water at 30°C. What is the solubility of the solute?
(d) Draw and label a typical solubility curve.
4. Mass/Volume and Molar Quantities
(a) Define mole.
(b) Calculate the number of moles in 9g of water (H₂O = 18g/mol).
(c) Calculate the volume occupied by 3 moles of a gas at s.t.p. (1 mole = 22.4 dm³).
5. Acid-Base Reactions and Indicators
(a) What is a standard solution?
(b) Name two indicators used in acid-base titrations and state their colour changes in acid and base.
(c) Write a balanced equation for the reaction between HCl and NaOH.
6. Titration Calculations
25.0 cm³ of a solution of HCl required 20.0 cm³ of 0.10 mol/dm³ NaOH for neutralization. Calculate the concentration of the HCl solution in mol/dm³.
7. Hydrocarbons: Classification
(a) Define hydrocarbons.
(b) Classify the following as alkanes, alkenes, alkynes or aromatic hydrocarbons: (i) CH₄ (ii) C₂H₄ (iii) C₆H₆
(c) State two characteristics of organic compounds.
8. Alkanes and Alkenes
(a) Write the general formula for alkanes.
(b) Name and draw the structure of the first four alkanes.
(c) Describe one chemical test used to distinguish between alkanes and alkenes.
9. Benzene and Aromatic Hydrocarbons
(a) Describe the structure of benzene.
(b) Write two uses of benzene.
(c) Why is benzene classified as an aromatic compound?
10. Alkanols (Alcohols)
(a) What is the functional group of alcohols?
(b) Describe one method of preparing ethanol in the laboratory or industry.
(c) List two uses and two physical properties of ethanol.
Section C: Objective Answers
- C — Water is called a universal solvent because it dissolves many substances.
- B — Hard water contains calcium and magnesium ions.
- A — Temporary hardness is removed by boiling.
- B — Cobalt (II) chloride paper turns pink in the presence of water.
- C — Water has a bent (angular) structure due to lone pairs on oxygen.
- D — Chlorination is a common method for municipal water purification.
- C — Solubility is the maximum amount of solute that dissolves in 100g of solvent at a given temperature.
- C — Temperature affects the solubility of most substances.
- B — A solubility curve shows solubility against temperature.
- B — Molar mass of water = 2(1) + 16 = 18 g/mol.
- C — The mole measures amount of substance with same number of particles as in 12g of carbon-12.
- B — 1 mole of any gas occupies 22.4 dm³ at s.t.p.
- A — HCl is a strong acid.
- A — Methyl orange turns from yellow to red in acidic solution.
- C — A standard solution is one with known concentration.
- B — The end point in titration is observed through colour change of indicator.
- B — Carbon forms 4 covalent bonds due to tetravalency.
- B — Organic compounds are carbon-based.
- B — Hydrocarbons contain only hydrogen and carbon.
- B — Alkanes are saturated hydrocarbons.
- C — The general formula for alkanes is CnH2n+2.
- B — C3H8 (propane) is an alkane.
- C — Alkenes have a double bond (C=C).
- C — Ethene (C2H4) is an alkene.
- C — Alkynes contain a triple bond (C≡C).
- B — General formula for alkynes is CnH2n-2.
- C — Benzene is an aromatic hydrocarbon.
- A — Benzene’s formula is C6H6.
- B — Benzene is an unsaturated hydrocarbon with alternating double bonds.
- B — Alkanols contain the hydroxyl (-OH) group.
- B — Ethanol is made industrially by fermentation.
- B — Ethanol boils at around 78°C.
- C — Ethanol is a good solvent.
- B — Alcohols are classified by the number of -OH groups.
- A — Ethanol is a primary alcohol.
- A — The formula of ethanol is C2H5OH.
- C — Ethanol is used in perfumes and as fuel.
- A — Phenolphthalein is used in acid-base titrations.
- B — Relative molecular mass of CO₂ is 12 + 2(16) = 44.
- B — 2 moles of gas at s.t.p. occupy 2 × 22.4 = 44.8 dm³.
Section D: Theory Answers
1. Water: Sources and Structure
(a) Two natural sources of water:
- Rainwater
- Underground water (wells, springs)
(b) Water is referred to as a universal solvent because it can dissolve a wide variety of substances solids, liquids, and gases more than any other known liquid. This property makes it very useful in chemical reactions and biological processes.
(c) Water has an angular (bent) molecular structure. It consists of two hydrogen atoms covalently bonded to one oxygen atom, forming an angle of approximately 104.5°. This gives water its polar nature.
2. Hardness and Purification of Water
(a)
- Temporary hardness is caused by the presence of dissolved bicarbonates of calcium and magnesium.
- Permanent hardness is caused by the presence of chlorides or sulfates of calcium and magnesium.
(b)
- Temporary hardness can be removed by boiling.
- Permanent hardness can be removed by adding washing soda (sodium carbonate).
(c) Three steps in municipal water purification:
- Sedimentation – large particles settle.
- Filtration – removal of smaller impurities.
- Chlorination – adding chlorine to kill pathogens.
3. Solubility and Solutions
(a) Solubility is defined as the maximum amount of solute that can dissolve in 100 g of solvent at a specific temperature to form a saturated solution.
(b) Two factors that affect solubility:
- Temperature
- Nature of solute and solvent
(c) Solubility = (mass of solute ÷ mass of solvent) × 100
= (25 ÷ 100) × 100 = 25 g/100 g of water
(d) (See diagram of solubility curve – a line graph of temperature on X-axis and solubility on Y-axis, generally rising with temperature)
4. Mass/Volume and Molar Quantities
(a) A mole is the amount of substance that contains as many particles as there are atoms in 12 grams of carbon-12.
(b) Moles = Mass ÷ Molar Mass = 9g ÷ 18g/mol = 0.5 moles
(c) Volume = Moles × Molar volume = 3 × 22.4 = 67.2 dm³
5. Acid-Base Reactions and Indicators
(a) A standard solution is a solution whose concentration is accurately known.
(b) Indicators and colour changes:
- Methyl orange: red in acid, yellow in base
- Phenolphthalein: colourless in acid, pink in base
(c) Balanced equation:
HCl + NaOH → NaCl + H₂O
6. Titration Calculations
Given:
- Volume of HCl = 25.0 cm³ = 0.025 dm³
- Volume of NaOH = 20.0 cm³ = 0.020 dm³
- Concentration of NaOH = 0.10 mol/dm³
Balanced equation: HCl + NaOH → NaCl + H₂O
Using: C₁V₁ = C₂V₂
Let concentration of HCl = C₁
C₁ × 0.025 = 0.10 × 0.020
C₁ = (0.10 × 0.020) ÷ 0.025 = 0.08 mol/dm³
7. Hydrocarbons: Classification
(a) Hydrocarbons are organic compounds made up of only carbon and hydrogen.
(b) Classification:
- CH₄ – Alkane
- C₂H₄ – Alkene
- C₆H₆ – Aromatic hydrocarbon
(c) Characteristics of organic compounds:
- Covalent bonding
- Low melting and boiling points
8. Alkanes and Alkenes
(a) General formula of alkanes: CnH2n+2
(b) First four alkanes:
- Methane: CH₄
- Ethane: C₂H₆
- Propane: C₃H₈
- Butane: C₄H₁₀
(c) Test to distinguish:
- Alkenes decolourize bromine water, alkanes do not.
9. Benzene and Aromatic Hydrocarbons
(a) Benzene has a ring structure with six carbon atoms and alternating double bonds (resonance structure).
(b) Uses:
- Manufacture of plastics
- Solvent for chemical reactions
(c) Benzene is classified as aromatic because it contains a conjugated ring system with delocalized electrons.
10. Alkanols (Alcohols)
(a) Functional group: –OH (hydroxyl group)
(b) Industrial preparation of ethanol:
- Fermentation of glucose using yeast: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
(c) Uses:
- As fuel
- In perfumes
Physical properties:
- Colorless liquid
- Boils at 78°C
Student-Focused Conclusion
To succeed in Chemistry, mastering each week’s topic is crucial. Revisit water purification processes, solve mole concept problems, and understand hydrocarbons deeply. Regular revision, consistent problem-solving, and practicing past questions will boost your confidence.
Avoid shortcuts in preparation. Focus on understanding principles rather than cramming. Remember, integrity during exams is key to academic success.
