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Grade 12 Chemistry national exam, 2014 E.C. (2022 G.C.)
61 questions · 120 minutes. The first 5 answers are shown with explanations; sit the whole paper timed in the app to get your score and the textbook page behind every question.
- 1.What is the difference between reversible and irreversible reactions?
- A. In reversible reactions, the reaction goes to completion.
- B. In irreversible reactions, there is a mixture of products and reactants.
- C. In reversible reactions, there is equilibrium between reactants and products.
- D. In irreversible reactions, there is equilibrium between reactants and products.
Answer: C. This question tests the difference between reversible and irreversible reactions. A reversible reaction can proceed in both directions and reach equilibrium between reactants and products, so C is correct. A describes completion, not a reversible reaction; B describes a possible mixture but not the defining difference; D wrongly says an irreversible reaction reaches equilibrium. Textbook: Grade 11, unit 5 · section 5.2.1. - 2.Consider the reactions all given below are in gaseous state. For which of the following reactions is K p less than K c ?
- A. N 2 O 4 ⇌ 2NO 2
- B. 2SO 2 + O 2 ⇌ 2SO 3
- C. 2H 2 ⇌ H 2 + I 2
- D. N 2 + O 2 ⇌ 2NO
Answer: B. The key idea is that the change in gas moles is products minus reactants. $K_p=K_c(RT)^{\Delta n}$, so when $\Delta n<0$, $K_p<K_c$. In B, $\Delta n=2-3=-1$, so it fits; A has $\Delta n=+1$, while C and D have $\Delta n=0$, so they do not. Textbook: Grade 11, unit 5 · section 5.2.4. - 3.The heating curve shown below shows a substance in the solid, liquid and gas phase. Which segment represents only the liquid phase?
- A. 3
- B. 5
- C. 1
- D. 2
- 4.What is enthalpy change? It is
- A. the amount of heat given out or absorbed in a reaction at constant pressure and volume
- B. the amount of heat absorbed in a reaction
- C. the amount of heat given out in a reaction
- D. the amount of heat given out or absorbed in a reaction at constant pressure
Answer: D. Enthalpy change is the heat absorbed or released during a reaction at constant pressure. D states this. A incorrectly adds constant volume, while B and C describe only heat absorbed or only heat released. Textbook: Grade 10, unit 4 · section 4.1. - 5.What is oxidation? Oxidation is
- A. the addition of electron(s) to the oxidizing agent
- B. the reduction of the oxidation state of the oxidizing agent
- C. the addition of hydrogen to a substance and the removal of oxygen from a substance
- D. the loss of electrons by a species, accompanied by an increase in oxidation number
Answer: D. Oxidation means losing electrons, which increases a species’ oxidation number. D gives this definition. A describes electron gain, B describes a decrease in oxidation number, and C describes reduction by hydrogen gain or oxygen loss. Textbook: Grade 10, unit 1 · section 1.4. - 6.What is meant by preferential discharge, if a number of ions are present in a solution? It means that the one which requires
- A. highest energy will be liberated first at a given electrode
- B. highest energy will be liberated last at a given electrode
- C. least energy will be liberated first at a given electrode
- D. least energy will be liberated last at a given electrode
Answer: C. The key idea is that preferential discharge means the ion that needs the least energy is released first at an electrode. Therefore, the ion requiring the least energy is discharged first, as stated in C. A says highest energy first; B says highest energy last; D says least energy last. Textbook: Grade 12, unit 2 · section 2.2.3. - 7.Which of the following is a property of covalent compounds? Covalent compounds
- A. is generally insoluble in water
- B. is crystalline solids at room temperature
- C. is non-volatile
- D. has high melting and boiling points
Answer, explanation and textbook page: open in the app. - 8.Which of the following is a covalent molecule?
- A. [NH4]+
- B. CO3-
- C. PCl3
- D. NaCl
Answer, explanation and textbook page: open in the app. - 9.What is the concentration of a solution? It is
- A. the amount of solute needed to make a concentrated solution
- B. number of moles of solute and number of moles of solvent
- C. the quantity of solute in a given quantity of solution
- D. the amount of solvent needed to dissolve a solute
Answer, explanation and textbook page: open in the app. - 10.How many moles of C 12 H 22 O 11 (sucrose Molecular weight= 342.91 g/mol) is needed there to prepare 2.0 L of 0.3 M solution?
- A. 0.6
- B. 6.6
- C. 0.15
- D. 0.43
Answer, explanation and textbook page: open in the app. - 11.At 75°C, the vapor pressure of pure water is 39 kPa. Which one of the vapor pressure of a solution obtained by dissolving 34.2 g sucrose in 180 mL of water? (Assume that the density of water is 1.000 g/mL)
- A. 41.1 kPa
- B. 44.5 kPa
- C. 31.2 kPa
- D. 38.6 kPa
Answer, explanation and textbook page: open in the app. - 12.Which of the following statements is NOT true about the colligative properties of electrolytes and non-electrolytes?
- A. The effect of non-electrolytes on colligative properties is very low compared to electrolytes
- B. The effect of non-electrolytes on colligative properties is the same as those of electrolytes
- C. The effect of electrolytes on colligative properties is very high compared to non-electrolytes
- D. The colligative properties of non-electrolytes are not considerably changed
Answer, explanation and textbook page: open in the app. - 13.What is the purpose of synthetic cryolite in the extraction of aluminum by the Hall's process?
- A. Cryolite increases the melting point of alumina.
- B. Cryolite is used as a catalyst in the extraction of aluminum.
- C. Cryolite increases the purity of the extracted aluminum.
- D. Cryolite reduces the melting point of alumina.
Answer, explanation and textbook page: open in the app. - 14.Which of the following is a chemical property of aluminum?
- A. Aluminum is a good conductor of heat and electricity.
- B. Aluminum has a lower density than any other commercial metal.
- C. Aluminum liberates hydrogen gas from dilute acids like HCl and H 2 SO 4 .
- D. Aluminum is a grey metal in color.
Answer, explanation and textbook page: open in the app. - 15.For the reaction shown below, which of the following is a conjugate acid-base pair? HC 3 O -(aq) + H 2 O(l) ⇌ H 3 O + + CO 3 2-
- A. H 3 O + and HCO 3 -
- B. HCO 4 - and CO 4 2-
- C. HCO 3 - and H 2 O
- D. H 2 O and CO 2
Answer, explanation and textbook page: open in the app. - 16.How can a project of establishing an industry that consumes coal affect the environment?
- A. Production of high level of lead in the atmosphere
- B. By changing the pH of water
- C. Increment in concentration of nitric oxide
- D. Rise in global temperature
Answer, explanation and textbook page: open in the app. - 17.Which of the following is a fundamental quantity SI unit?
- A. Pressure
- B. Length
- C. Speed
- D. Force
Answer, explanation and textbook page: open in the app. - 18.Which of the following postulates of Dalton's atomic theory was modified by the modern atomic theory?
- A. Atoms are neither created nor destroyed in chemical reactions
- B. Compounds are formed when atoms of more than one element combine
- C. Atoms are the smallest particles of all elements
- D. Atoms are indivisible and indestructible
Answer, explanation and textbook page: open in the app. - 19.Which of the following includes all of the known atomic models?
- A. Bohr Model, Rutherford Mechanical Model
- B. Thomson Model, Dalton's Atomic Model
- C. Bohr Model, Thomson Model, Rutherford Model, Dalton's Atomic Model
- D. Valence Bond Model, Quantum Mechanical Model, Thomson Model, Rutherford Model
Answer, explanation and textbook page: open in the app. - 20.What does Mendeleev's Periodic Law state? Properties of elements are
- A. periodic functions of their electron configurations
- B. atomic radius
- C. atomic numbers
- D. atomic masses
Answer, explanation and textbook page: open in the app. - 21.What is the mole ratio of oxygen gas to carbon dioxide gas in the following reaction? C 3 H 8 (g) + 5O 2 (g) → 3CO 2 (g) + 4H 2 O (l)
- A. 2 mole oxygen gas to 3 mole carbon dioxide
- B. 7 mole oxygen gas to 5 mole carbon dioxide
- C. 10 mole oxygen gas to 6 mole carbon dioxide
- D. 5 mole oxygen gas to 3 mole carbon dioxide
Answer, explanation and textbook page: open in the app. - 22.Consider the following chemical equation for the combustion of ethane (C 2 H 6 ) in the presence of oxygen to produce carbon dioxide and water: C 2 H 6 (g) + 7O 2 (g) → 4CO 2 (g) + 6H 2 O (l) In this reaction:
- A. Water is formed at a rate equal to 2/3 the rate of formation of CO 2
- B. CO 2 is formed twice as fast as ethane is consumed
- C. The rate of consumption of ethane is 7 times faster than the rate of consumption of oxygen
- D. The rate of formation of CO 2 equals the rate of formation of water
Answer, explanation and textbook page: open in the app. - 23.The electron configuration of Cu (Z=29) is:
- A. [Kr]4s 2 3d 9
- B. [Ar]4s 2 3d 10
- C. [Ar]4s 2 3p 8
- D. [Ar]4s 2 4d 9
Answer, explanation and textbook page: open in the app. - 24.How does a catalyst increase the rate of a reaction?
- A. By lowering the activation energy
- B. By changing the equilibrium constant
- C. By forming an intermediate complex
- D. By increasing the activation energy
Answer, explanation and textbook page: open in the app. - 25.Which of the following statements correctly describes Boyle's Law?
- A. The volume of a gas at a given temperature is proportional to the square root of the applied pressure
- B. The volume of a gas at a given temperature is inversely proportional to the square root of the applied pressure
- C. The volume of a gas at a given temperature is directly proportional to the applied pressure
- D. The volume of a gas at a given temperature is inversely proportional to the applied pressure
Answer, explanation and textbook page: open in the app. - 26.Among the following reactions, which one shows a coordinate covalent bond formation?
- A. H - + ·Cl : → H-Cl
- B. H - + ·H → H:H
- C. C
- D. D
Answer, explanation and textbook page: open in the app. - 27.Which of the following belongs to chemical bonding theories?
- A. Molecular orbital theory and kinetic-molecular theory
- B. Valence bond theory and valence shell electron pair repulsion theory
- C. Kinetic-molecular theory and valence shell electron pair repulsion theory
- D. Valence bond theory and molecular orbital theory
Answer, explanation and textbook page: open in the app. - 28.In which of the following molecules is the central atom sp 2 hybridized?
- A. SO 2
- B. CO
- C. CO 2
- D. N 2 O
Answer, explanation and textbook page: open in the app. - 29.The half-life of a reaction is the time taken for the
- A. rate constant to decrease by 50% of its initial value
- B. complete conversion of a reactant into a product
- C. reactant concentration to decrease by 50% of its initial value
- D. rate constant to increase by 50% of its initial value
Answer, explanation and textbook page: open in the app. - 30.In the scientific method, a predictive statement that can be tested experimentally is:
- A. proof
- B. hypothesis
- C. truth
- D. evidence
Answer, explanation and textbook page: open in the app. - 31.Which of the following is NOT true about cathode rays? Cathode rays
- A. contain particles, which are positively charged
- B. are common constituents of all matter and their m/e is constant for all gases
- C. contain particles, which are negatively charged
- D. travel in straight lines from cathode to the anode
Answer, explanation and textbook page: open in the app. - 32.Which of the following statements is correct about the energy of a photon?
- A. It is directly related to the intensity of the light
- B. It is directly proportional to the wavelength of the light
- C. It is directly proportional to the observed frequency of the light
- D. It is inversely proportional to the observed frequency of the light
Answer, explanation and textbook page: open in the app. - 33.Which of the following explains the emission spectra of atoms consisting of a series of fine lines?
- A. The energy of the atoms is continuous with discrete frequencies
- B. An electron that revolves around the nucleus emits specific energy values in an atom
- C. An electron can have specific transition by energy changes corresponding to photon of specific wavelength
- D. An electron undergoes a transition by energy changes corresponding to photon of specific wavelength
Answer, explanation and textbook page: open in the app. - 34.For a reaction: ½ A → the rate of disappearance of 'A' is related to the appearance of 'B' by the expression:
- A. -Δ[A]/Δt = 1/2 Δ[B]/Δt
- B. Δ[A]/Δt = 1/4 Δ[B]/Δt
- C. -Δ[A]/Δt = Δ[B]/Δt
- D. Δ[A]/Δt = 4Δ[B]/Δt
Answer, explanation and textbook page: open in the app. - 35.Which of the following does represent a general property of a base?
- A. Soluble bases release hydronium ion in aqueous solution
- B. Aqueous solution of bases turns methyl orange to red
- C. Solutions of strong bases are good conductors of electricity
- D. Aqueous solution of bases turns blue litmus paper to red
Answer, explanation and textbook page: open in the app. - 36.For the conversion of 3.5 yards into meter using the factor label method, which of the following is the correct step?
- A. (3.5 yards/1)(3.5 feet/1 yard)(12 in/1 foot)(1 in/2.54 cm)(1 m/100 cm)
- B. (3.5 yards/1)(3.5 feet/1 yard)(12 in/1 foot)(2.54 cm/1 in)(1 m/100 cm)
- C. (3.5 yards/1)(1 yard/3.5 feet)(12 in/1 foot)(2.54 cm/1 in)(1 m/100 cm)
- D. (3.5 yards/1)(1 yard/3.5 feet)(12 in/1 foot)(1 in/2.54 cm)(1 m/100 cm)
Answer, explanation and textbook page: open in the app. - 37.The process in which a compound absorbs electrical energy and decomposes into its elements is
- A. hydrolysis
- B. electropating
- C. electrolysis
- D. solvolysis
Answer, explanation and textbook page: open in the app. - 38.Which of the following is true about galvanic cells used in commercial lead storage batteries? In lead storage batteries,
- A. half of the galvanic cells are connected in series
- B. the galvanic cells are made up of PbO 2 of anodes
- C. galvanic cells are connected in series
- D. galvanic cells are connected in parallel
Answer, explanation and textbook page: open in the app. - 39.Sodium carbonate is a basic salt because it is a salt of
- A. a weak acid and a weak base and the cation of the weak base can be hydrolyzed
- B. a strong acid and a weak base and the anion of the strong acid can be hydrolyzed
- C. a strong base and a weak acid and the anion of the weak acid can be hydrolyzed
- D. a strong base and a strong acid and the anion of the strong acid can be hydrolyzed
Answer, explanation and textbook page: open in the app. - 40.Which of the following statements is true for an acid-base titration?
- A. An acid-base titration is a method of quantitative analysis for determining the concentration of an acid or base
- B. An acid-base titration is a method of qualitative analysis for determining the concentration of an acid or base
- C. Indicators catalyze an acid-base titration to show the inflection point of the titration curve
- D. Acid-base titrations cannot be carried out in the absence of indicators
Answer, explanation and textbook page: open in the app. - 41.What is the change in internal energy (ΔE) for a reaction, in which the system absorbs 650 J of heat and 125 J of work is done on the system?
- A. -775 J
- B. -535 J
- C. 775 J
- D. 535 J
Answer, explanation and textbook page: open in the app. - 42.Which statement describes the formation of a covalent bond? In covalent bond electrons are
- A. shared between non-metallic atoms
- B. transferred from non-metallic atoms to metallic atoms
- C. shared between metallic atoms
- D. transferred from metallic atoms to non-metallic atoms
Answer, explanation and textbook page: open in the app. - 43.How do the elements of Group IIA form ions?
- A. By losing 2 electrons
- B. By gaining 2 electrons
- C. By gaining one electron
- D. By losing one electron
Answer, explanation and textbook page: open in the app. - 44.How is hydrogen bonding formed? It is formed when a hydrogen atom is bonded to
- A. highly electronegative elements, chlorine, oxygen and nitrogen
- B. highly electronegative elements, fluorine, oxygen and nitrogen
- C. highly electronegative elements, fluorine, chlorine and oxygen
- D. highly electronegative elements, fluorine, oxygen and phosphorus
Answer, explanation and textbook page: open in the app. - 45.Which one of the following types of energy change occurs from the combustion of carbon in oxygen?
- A. heat energy
- B. solar energy
- C. light energy
- D. electrical energy
Answer, explanation and textbook page: open in the app. - 46.The self-ionization of water can be expressed by the equation: H 2 O(l) + H 2 O(l)⇌ H 3 O + (aq) + OH - (aq) Which of the following is the correct expression of the ionic product of water?
- A. K w = [H 3 O + ][OH - ]
- B. K w = [H 2 O][OH - ]/[H 3 O + ]
- C. K w = [H 3 O + ][HO - ]
- D. K w = [H 3 O + ][OH - ]
Answer, explanation and textbook page: open in the app. - 47.What is the effect of a common ion in an electrolytic solution?
- A. It decreases the solubility of a solute
- B. It has no effect on the pH of a solution
- C. It suppresses the ionization of a weak acid and raises the pH
- D. It suppresses the ionization of a weak base and lowers the pOH
Answer, explanation and textbook page: open in the app. - 48.Consider a bottle containing water, water vapor and air in equilibrium. If the temperature decreases slightly, the amount of water vapor:
- A. will decrease and the vapor pressure will increase
- B. and vapor pressure will decrease
- C. and vapor pressure will increase
- D. will increase and the vapor pressure will decrease
Answer, explanation and textbook page: open in the app. - 49.Why do water droplets collect on the outside of a glass of water on a hot day?
- A. There will be a condensation of water vapor on the glass
- B. There will be a sublimation of water vapor on the outside of a glass
- C. There is heat exchange between the water in the glass and the surrounding
- D. Water from the glass starts to vaporize
Answer, explanation and textbook page: open in the app. - 50.What are hydrocarbons? Compounds that contain
- A. benzene rings only
- B. benzene and its derivatives only
- C. hydrogen and carbon with no benzene rings
- D. hydrogen and carbon only
Answer, explanation and textbook page: open in the app. - 51.Which of the following statement is INCORRECT regarding the boiling points of alkanes?
- A. Boiling points of straight chain alkanes is greater than that of branched chain alkanes
- B. The boiling point of cycloalkanes is higher than that of linear alkanes
- C. Boiling points increases with stronger Van der Waals forces
- D. Surface area is the only factor that determines the boiling points of alkanes
Answer, explanation and textbook page: open in the app. - 52.Which of the following statements is NOT correct about minerals and ores?
- A. Minerals are the natural forms in which various metals exist
- B. Ores are usually used to extract metals economically
- C. All minerals are ores
- D. All ores are minerals
Answer, explanation and textbook page: open in the app. - 53.Why is CaCl₂ added to NaCl in a 1:1⁄2 ratio in the Down's cell for the manufacturing of sodium metal?
- A. CaCl₂ is used to lower the density of the mixture
- B. CaCl₂ is used as an electrolyte
- C. CaCl₂ is used as a catalyst
- D. CaCl₂ is used to lower the melting temperature of NaCl
Answer, explanation and textbook page: open in the app. - 54.Which of the following is NOT a major step in metallurgical processes?
- A. Pretreatment
- B. Extracting the metal and refining
- C. Mining the ore
- D. Concentrating the ore
Answer, explanation and textbook page: open in the app. - 55.Which monomers are used for the synthesis of Teflon?
- A. Styrene and Phenol
- B. Tetrafluoroethylene
- C. Isoprene
- D. Propylene
Answer, explanation and textbook page: open in the app. - 56.What is the rate of dissolution? It is
- A. the rate at which a solid dissociates
- B. the speed at which a solid sublimes
- C. the rate at which a solid turns to liquid
- D. the speed at which a solid substrate goes into solution
Answer, explanation and textbook page: open in the app. - 57.Which one of the following is correctly stated regarding solubility as an equilibrium process?
- A. Supersaturated solution is a solution that contains more than the equilibrium amount of dissolved solute
- B. Supersaturated solution is more stable than saturated solution
- C. Unsaturated solution is a solution that is in equilibrium with respect to a given dissolved substance
- D. Unsaturated solution is a solution in which more of the solute can be dissolved
Answer, explanation and textbook page: open in the app. - 58.Which of the following carboxylic acids is a solid substance at room temperature?
- A. Nonanoic acid
- B. Decanoic acid
- C. Heptanoic acid
- D. Octanoic acid
Answer, explanation and textbook page: open in the app. - 65.What is the IUPAC name of an ester having the molecular formula C₄H₉O₂?
- A. Ethyl butyrate
- B. Pentyl butyrate
- C. Ethyl butanoate
- D. Methyl butyrate
Answer, explanation and textbook page: open in the app. - 66.What is the formula of pentanoic acid?
- A. CH₃(CH₂)₃COOH
- B. CH₃(CH₂)₄COOH
- C. CH₃(CH₂)₂COOH
- D. CH₃(CH₂)₃COOH
Answer, explanation and textbook page: open in the app. - 70.Which of the following represents the structure of a disaccharide?
- A. A
- B. B
- C. C
- D. D
Answer, explanation and textbook page: open in the app.