Gobezoch › Past exams › Chemistry

Grade 12 Chemistry national exam, 2009 E.C. (2017 G.C.)

68 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.

Sit this paper (timed)Practice mode
  1. 1.Which of the following covalent bonds is the most polar?
    • A. H - F
    • B. H - C
    • C. H - H
    • D. H - N
    Answer: A. The key idea is that a bond is more polar when its atoms have a larger difference in electronegativity, meaning their pull on shared electrons differs more. Fluorine pulls electrons much more strongly than hydrogen, so $\mathrm{H-F}$ is the most polar bond listed. $\mathrm{H-C}$ and $\mathrm{H-N}$ have smaller differences; $\mathrm{H-H}$ has no difference. Textbook: Grade 9, unit 5 · section 5.3.
  2. 2.The force that hold different atoms or ions together are called?
    • A. Electric forces
    • B. Physical bonds
    • C. Chemical bond
    • D. Atomic forces
    Answer: C. A chemical bond is the force that holds atoms or ions together. The name for this holding force is a chemical bond. A is too general; B is not the correct term; D is not the correct term. Textbook: Grade 11, unit 2 · section 2.3.2.
  3. 3.How many electrons are shared between two atoms in a double bond?
    • A. 2
    • B. 3
    • C. 4
    • D. 6
    Answer: C. The question tests how many electrons make a double bond. A double bond contains two shared pairs, so it has $2\times2=4$ shared electrons. A gives one shared pair, or $2$ electrons. B gives $3$ electrons, not a whole number of shared pairs. D gives three shared pairs, which is a triple bond. Textbook: Grade 9, unit 5 · section 5.3.
  4. 4.What is the chemical formula of the compound formed by aluminium (III) and sulphate ion, $\mathrm{SO_4^{2-}}$ ?
    • A. $\mathrm{AlSO_4}$
    • B. $\mathrm{Al_2SO_4}$
    • C. $\mathrm{Al_2(SO_4)_3}$
    • D. $\mathrm{Al(SO_4)_3}$
    Answer: C. The key idea is that an ionic compound must have a total charge of zero. Aluminium ions have charge $+3$ and sulfate ions have charge $-2$, so $2(+3)+3(-2)=0$ and the formula is $\mathrm{Al_2(SO_4)_3}$. A is wrong because its charges do not balance; B is wrong because its charges do not balance; D is wrong because its charges do not balance. Textbook: Grade 9, unit 5 · section 5.2.
  5. 6.Which of the following is the correct order for electrons filling in orbitals?
    • A. 3s, 3p, 4s, 3d
    • B. 2p, 3s, 3p, 3d
    • C. 3p, 4s, 3d, 5s
    • D. 4s, 3d, 4p, 4d
    Answer: A. According to the Aufbau principle (the (n + l) rule), the filling order of orbitals is 3s (n+l = 3), 3p (n+l = 4), 4s (n+l = 4, lower n), and then 3d (n+l = 5). Textbook: Grade 11, unit 1 · section 1.7.
  6. 7.The normal human eye responds to visible light of wavelength ranging from about 390nm to 710nm. What is the frequency range of the human eye? 7.7 × 10 s 14 −1 4.2 × 10 s 14 −1 4.2 × 10 s 14 −1 7.7 × 10 s 14 −1
    • A. to
    • B. to 1.3 × 10 s −15 −1 2.4 × 10 s −15 −1 2.4 × 10 s −15 −1 1.3 × 10 s −15 −1
    • C. to
    • D. to
    Answer, explanation and textbook page: open in the app.
  7. 8.How many different types of orbitals are there in the third energy level?
    • A. 2
    • B. 3
    • C. 6
    • D. 7
    Answer, explanation and textbook page: open in the app.
  8. 9.The Heisenberg uncertainty principle states that
    • A. Two atoms of the same element must have the same number of protons.
    • B. No two electrons din the same atom can have the same set of four quantum numbers.
    • C. It is impossible to determine both position and momentum of an electron simultaneously.
    • D. Electrons of atoms in ground state enter energetically equivalent stet of orbitals singly before they pair any orbitals of the set.
    Answer, explanation and textbook page: open in the app.
  9. 10.Which of the following transitions will have minimum wavelength?
    • A. n4 n1
    • B. n2 n1 → → → →
    • C. n4 n2
    • D. n3 n1
    Answer, explanation and textbook page: open in the app.
  10. 11.What is the energy associated with one photon of a microwave radiation having a frequency of $2.45\times10^9\,\text{s}^{-1}$?
    • A. $1.62\times10^{24}\,\text{J}$
    • B. $2.45\times10^9\,\text{J}$
    • C. $2.45\times10^{-9}\,\text{J}$
    • D. $1.62\times10^{-24}\,\text{J}$
    Answer, explanation and textbook page: open in the app.
  11. 12.What is the frequency of a radiation (in Hz) from an atom if its wavelength is $1.0 \times 10^{-9}\,\text{nm}$?
    • A. $3.3 \times 10^{-27}$
    • B. $3.0 \times 10^{17}$
    • C. $3.0 \times 10^{8}$
    • D. $3.0 \times 10^{26}$
    Answer, explanation and textbook page: open in the app.
  12. 13.Which of the following particle was discovered by the cathode rays experiment?
    • A. Electron
    • B. Neutron
    • C. Nucleus
    • D. Proton
    Answer, explanation and textbook page: open in the app.
  13. 14.Which of the following is NOT a laboratory safety rule?
    • A. You should tie back loose hair.
    • B. You should never add acid to water.
    • C. Do not suck solution in the pipette by mouth.
    • D. When lighting a Bunsen Burner, you should light the match stick before turning on the gas.
    Answer, explanation and textbook page: open in the app.
  14. 15.Which of the following is the correct relationship between picometer (PM) and nanometer (nm)?
    • A. 1Pm = 10nm
    • B. 1pm = 100nm
    • C. 1nm = 10pm
    • D. 1nm = 1000pm
    Answer, explanation and textbook page: open in the app.
  15. 16.How many significant figures has the sum of 2.453, 4.6 and 8.14?
    • A. 2
    • B. 3
    • C. 4
    • D. 5
    Answer, explanation and textbook page: open in the app.
  16. 17.Which one of the following measurements has the greatest number of significant figures?
    • A. 0.00046
    • B. 0.0046
    • C. 460
    • D. $4.6\times10^6$
    Answer, explanation and textbook page: open in the app.
  17. 18.Which of the following methods is used to convert oils into fats?
    • A. Esterification reaction using strong bases like NaOH or KOH
    • B. Saponification reaction using strong bases like NaOH or KOH
    • C. Hydrolysis reaction in the presence of water and a catalyst
    • D. Hydrogenation reaction at high temperature and in the presence of a catalyst
    Answer, explanation and textbook page: open in the app.
  18. 19.The solubility of compounds containing the carboxylic acid group can be increased by reaction with
    • A. Sulphuric acid
    • B. Sodium hydroxide
    • C. Water
    • D. Benzoic acid
    Answer, explanation and textbook page: open in the app.
  19. 20.What products will be formed when a carboxylic acid reacts with an alcohol?
    • A. Ketone and water
    • B. Amide and water
    • C. Acid chloride and water
    • D. Easter and water
    Answer, explanation and textbook page: open in the app.
  20. 21.Consider the reaction What is the equilibrium constant expression if the initial concentration of , is 0.1M and the equilibrium concentration of A is expressed by x? (Assume the initial concentrations of A and B are both zero.) x −3x x.3
    • B. 0.1 −x (0.1 −3x)3 x −x3 x(3x)3
    • D. (0.1 −3x)3 0.1 −x
    Answer, explanation and textbook page: open in the app.
  21. 22.Consider the following reaction at equilibrium. $2\mathrm{CO_2}\,(\mathrm{g}) \rightleftharpoons 2\mathrm{CO}\,(\mathrm{g}) + \mathrm{O_2}\,(\mathrm{g})\ \Delta H^0 = -514\mathrm{KJ}$ What does Le Chatelier's principle predict when the temperature for the reaction is increased?
    • A. The value of the equilibrium constant will increase.
    • B. The value of the equilibrium constant will decrease.
    • C. The partial pressure of $\mathrm{O_2}\,(\mathrm{g})$ at equilibrium will increase.
    • D. The partial pressure of $\mathrm{CO_2}\,(\mathrm{g})$ at equilibrium will increase.
    Answer, explanation and textbook page: open in the app.
  22. 23.For one component system, when would the degree of freedom becomes one?
    • A. When only one phase is present.
    • B. When two phases are present at equilibrium.
    • C. When three phases are present at equilibrium.
    • D. At all times.
    Answer, explanation and textbook page: open in the app.
  23. 24.Which one of the following is correct when a reaction reaches equilibrium?
    • A. The reaction rate for the forward direction is decreased to zero.
    • B. The rate of the forward and reverse reaction becomes equal.
    • C. The rate of the reverse reaction is reached a maximum.
    • D. The amounts of reactants and products becomes equal.
    Answer, explanation and textbook page: open in the app.
  24. 25.A possible mechanism for the reaction, is Step: Slow Step: Fast Overall: According to the mechanism, what will be the rate law? K[B]2
    • A. Rate = K[A][B]
    • B. Rate = K[A][B]2
    • C. Rate =
    • D. Rate = K[A]
    Answer, explanation and textbook page: open in the app.
  25. 26.The initial rate of a reaction products was measured for several different starting concentrations of A and B, with the following results. Exp [A] [B] Initial rate of formation of C (M/s) 9.6 × 10−6 1 0.04 0.04 1.92 × 10−5 2 0.08 0.04 9.6 × 10−6 3 0.02 0.02 [A] 0 [B] What is the initial rate of reaction when = 0.12M and = 0.015M? 0 0.006Ms−1 0.006M s −2 −1
    • B. 1.08 × 10 Ms −5 −1 1.08 × 10 Ms −4 −1
    Answer, explanation and textbook page: open in the app.
  26. 27.Given the following data for the reaction: ] 4 + [N ] 2 − Experiment Rate 1 0.010M 0.020M 0.020M/s 2 0.015M 0.020M 0.03M/s 3 0.010M 0.010M 0.005M/s What will be the rate law for the given reaction? K[NH ][NO ] 4 + 2 − K[NH ] [NO ] 4 + 2 2 K[NH
    • A. Rate =
    • B. Rate = ] 4 + 2 2 −2 K[NH ] 4 + 2 −2 ] [NO ][NO
    • C. Rate =
    • D. Rate =
    Answer, explanation and textbook page: open in the app.
  27. 28.The rate of a reaction increases with increasing the concentration of reactant molecules, because
    • A. The average kinetic energy of the molecules increases.
    • B. The frequency of molecular collisions increase.
    • C. The order of the reaction increases
    • D. The activation energy increases.
    Answer, explanation and textbook page: open in the app.
  28. 29.Consider the following reactions: At a certain temperature, the rate of decomposition of is mol/s. What will be the rate of formation of ?
    • A. 1.0 x 10-5mol/s
    • B. 2.5 x 10-6mol/s
    • C. 1.3 x 10-6mol/s
    • D. 5.0 x 10-6mol/s
    Answer, explanation and textbook page: open in the app.
  29. 30.Which of the following refer to a reaction that is NOT dependent on the concentration of a reactant?
    • A. Second order reaction
    • B. First order reaction
    • C. Zero order reaction
    • D. Third order reaction
    Answer, explanation and textbook page: open in the app.
  30. 31.What is the bond order of a superoxide anion, with the chemical formula ?
    • A. 3
    • B. 2.5
    • C. 2
    • D. 1.5
    Answer, explanation and textbook page: open in the app.
  31. 32.What kind of hybrid orbitals are utilized by the carbon atom in $\mathrm{CF_4}$ molecules?
    • A. Sp
    • B. Sp$^2$
    • C. Sp$^3$
    • D. Sp$^3$d
    Answer, explanation and textbook page: open in the app.
  32. 33.Which statement about indicators is always correct?
    • A. The mid-point of the PH rage of an indicator is 7.0
    • B. The PH rage is greater with higher PKa values.
    • C. The colour red indicates an acidic solution.
    • D. The PKa values of the indicator is within its PH range.
    Answer, explanation and textbook page: open in the app.
  33. 34.The suppression of ionization of a weak acid or a weak base by adding one of its own ions is known as:
    • A. Buffer effect
    • B. Ionization effect
    • C. Common ion effect
    • D. Association effect
    Answer, explanation and textbook page: open in the app.
  34. 35.Nitrous acid, $\mathrm{HNO_2}$ is 0.37% ionized in 3.0M solution. What is the $K_a$ for this acid?
    • A. $\dfrac{3.0(0.0037)^2}{99.63}$
    • B. $\dfrac{(0.0037)^2}{0.9963}$
    • C. $\dfrac{3.0(0.0037)^2}{0.9963}$
    • D. $\dfrac{0.9963}{(0.0037)^2}$
    Answer, explanation and textbook page: open in the app.
  35. 36.Among the following acids, which has the lowest value?
    • B. HCOOH CH CH COOH 3 2 (CH )2CHCOOH 3 CH COOH 3
    Answer, explanation and textbook page: open in the app.
  36. 37.Which one of the following is a Lewis acid?
    • A. $\mathrm{NH_3}$
    • B. $\mathrm{CCl_4}$
    • C. $\mathrm{AlCl_3}$
    • D. $\mathrm{LiCl}$
    Answer, explanation and textbook page: open in the app.
  37. 38.Which of the following is the conjugate acid of the ion? H S 2 − S 2 −
    • B. S− H S 2
    Answer, explanation and textbook page: open in the app.
  38. 39.What will be the ration of the boiling point elevation of a 0.1M solution of sucrose, sodium sulphate and potassium bromide?
    • A. 1 : 3 : 1
    • B. 1 : 1 : 2
    • C. 1: 3 : 2
    • D. 1 : 2 : 2
    Answer, explanation and textbook page: open in the app.
  39. 40.When the molecular equation: Is written in terms of ionic equation, which one of the following pairs will be the spectator ions? Na+ Cl− Ca2+ Cl−
    • A. and
    • B. and Na 3 2− Cl− Ca2+ CO 3 2−
    • C. and
    • D. and
    Answer, explanation and textbook page: open in the app.
  40. 41.If 0.454kg of nitroglycerin explodes according to the following reaction: $2\mathrm{C_3H_5(NO_2)_3}\rightarrow 6\mathrm{CO_2}+3\mathrm{N_2}+5\mathrm{H_2}$ What is the total volume of gases in $\mathrm{dm^3}$ produced at STP?
    • A. 44.8
    • B. 163
    • C. 397.7
    • D. 650
    Answer, explanation and textbook page: open in the app.
  41. 42.How many grams of methanol would have to be added to water to prepare $150\text{ml}$ of solution which is $2.0\mathrm{M}$ methanol?
    • A. 2.4
    • B. 9.6
    • C. $9.6\times10^3$
    • D. $4.3\times10^2$
    Answer, explanation and textbook page: open in the app.
  42. 43.A certain 500g toothpaste sample has 0.2g of fluoride. What is the concentration of the fluoride in ppm?
    • A. 200
    • B. 250
    • C. 400
    • D. 1000
    Answer, explanation and textbook page: open in the app.
  43. 44.What will be the normality of a 2.3M sulphuric acid solution?
    • A. 0.23N
    • B. 0.46N
    • C. 2.3N
    • D. 4.6N
    Answer, explanation and textbook page: open in the app.
  44. 45.The solubility of NaCl in water at C is 36g in 100g of water. A solution that contains 18g of NaCl in 50g of 200 water at C is
    • A. Saturated
    • B. Unsaturated
    • C. Supersaturated
    • D. Dilute
    Answer, explanation and textbook page: open in the app.
  45. 46.Which of the following pairs of substances are miscible?
    • A. Water and gasoline
    • B. Water and oxygen
    • C. Water and salt
    • D. Water and ethanol
    Answer, explanation and textbook page: open in the app.
  46. 47.Which of the following types of solution are possible? 1. Solid dissolved in a liquid 2. Gas dissolved in a gas 3. Gas dissolved in a liquid 4. Solid dissolved in a solid
    • A. 1 and 2
    • B. 1, 2, 3 and 4
    • C. 1, 2 and 4
    • D. 1
    Answer, explanation and textbook page: open in the app.
  47. 48.The chemical makeup of oil is esters of glycerol with three
    • A. Identical saturated fatty acids.
    • B. Predominantly saturated fatty acids.
    • C. Predominantly unsaturated fatty acids.
    • D. Identical unsaturated fatty acids.
    Answer, explanation and textbook page: open in the app.
  48. 49.Which of the following general class of organic molecules do triglycerides belong to?
    • A. Ketones
    • B. Carboxylic acids
    • C. Esters
    • D. Ethers
    Answer, explanation and textbook page: open in the app.
  49. 50.What type of polymerization occurs when amino acids react to form peptides and proteins?
    • A. Addition polymerization
    • B. Condensation polymerization
    • C. Substitution polymerization
    • D. Hydration polymerization
    Answer, explanation and textbook page: open in the app.
  50. 51.Which of the following is the most abundant polysaccharide?
    • A. Amylose
    • B. Cellulose
    • C. Starch
    • D. Sucrose
    Answer, explanation and textbook page: open in the app.
  51. 52.What is the other name for polymethyl methacrylate (PMMA)?
    • A. Perspex
    • B. Teflon
    • C. Bakelite
    • D. Nylon- 6
    Answer, explanation and textbook page: open in the app.
  52. 53.What is the monomer of polyvinyl chloride (PVC)?
    • A. Cloroethane
    • B. Ethylene dichloride
    • C. Chloroform
    • D. Ethyl chloride
    Answer, explanation and textbook page: open in the app.
  53. 54.The second step in the production of sulphuric acid is given by the reaction: Which conditions would increase the yield of this reaction?
    • A. High temperature and low pressure
    • B. Low temperature and high pressure
    • C. High temperature and high pressure
    • D. Low temperature and low pressure
    Answer, explanation and textbook page: open in the app.
  54. 55.Which of the following reactions is used in the production of industrially important chemical?
    • B. H S O (l) + H O(l) →2H SO (aq) 2 2 7 2 2 4 3NO (g) + H O(l) →2HNO (aq) + NO (g) 3 2 3 2 (NH )2HPO (s) + NH (g) →NH H PO (s) 4 4 3 4 2 4 2Cr(s) + Al O (s) →Cr O (s) + 2Al(s) 2 3 2 3
    Answer, explanation and textbook page: open in the app.
  55. 56.Which one of the following metal is used for galvanization of iron sheets?
    • A. Nickel
    • B. Zinc
    • C. Chromium
    • D. Aluminium
    Answer, explanation and textbook page: open in the app.
  56. 57.In what way is the phosphorous cycle differs from the carbon and nitrogen cycle?
    • A. Phosphorus is more abundant than carbon and nitrogen
    • B. Phosphorus is less important than carbon and nitrogen
    • C. Phosphorus, once used by an organism does not cycle back to the environment
    • D. The reservoirs for phosphorus exists in mineral form in rocks than in the atmosphere
    Answer, explanation and textbook page: open in the app.
  57. 58.Which one of the following is needed for photosynthesis?
    • A. Carbon dioxide
    • B. Nitrogen
    • C. Oxygen
    • D. Phosphorus
    Answer, explanation and textbook page: open in the app.
  58. 59.Consider the reaction: , E0 = 0.78V What is the value of E when [Cu ] 2+ [Fe ] 2+ is equal to 0.040M and is equal to 0.40M?
    • A. 0.72V
    • B. 0.75V
    • C. 0.81V
    • D. 0.84V
    Answer, explanation and textbook page: open in the app.
  59. 60.For the electrochemical cell represented by: The standard reduction potentials for and are +0.34 and -0.76V, respectively, what will be the cell reaction that occurs spontaneously and its cell voltage? Cu + Zn = Cu + Zn 2+ 2+ E (V) 0 Zn + Cu = Zn + Cu 2+ 2+ E (V) 0
    • A. = 1.10
    • B. = 0.42 Cu + Zn = Zn + Cu 2+ 2+ E (V) 0 Cu + Zn = Cu + Zn 2+ 2+ E (V) 0
    • C. = 0.42
    • D. = 1.10
    Answer, explanation and textbook page: open in the app.
  60. 61.What product(s) is /are formed during the electrolysis of a concentrated aqueous solution of sodium chloride?
    • A. $\mathrm{Cl_2(g)}$
    • B. $\mathrm{Cl_2(g)}$ and $\mathrm{H_2(g)}$
    • C. $\mathrm{NaOH(aq)}$ and $\mathrm{Cl_2(g)}$
    • D. $\mathrm{Cl_2(g)}$, $\mathrm{H_2(g)}$ and $\mathrm{NaOH(aq)}$
    Answer, explanation and textbook page: open in the app.
  61. 62.In the reaction: $\mathrm{Pb} + (s),\ \mathrm{PbO_2} + \mathrm{H_2SO_4(aq)} \rightarrow 2\mathrm{PbSO_4(s)} + 2\mathrm{H_2O(l)}$ Which substance behaves as the oxidizing agent?
    • A. Pb
    • B. PbSO₄
    • C. PbO₂
    • D. H₂SO₄
    Answer, explanation and textbook page: open in the app.
  62. 63.What mass of magnesium (Mg) is produced in the electrolysis of molten $\mathrm{MgCl_2}$, if a current of $7.50 \times 10^2\,\text{A}$ is passed through the molten salt for 1.00 hour?
    • A. $3.4 \times 10^2\text{g}$
    • B. $9.92 \times 10^2\text{g}$
    • C. $1.7 \times 10^2\text{g}$
    • D. $4.96 \times 10^2\text{g}$
    Answer, explanation and textbook page: open in the app.
  63. 64.Devices in which oxidation- reduction reaction is induced by an electric current are called
    • A. Galvanic cells
    • B. Electrolytic cells
    • C. Voltaic cells
    • D. Electromotive cells
    Answer, explanation and textbook page: open in the app.
  64. 65.In the following reaction: 3Cl (aq) + 4CrO (aq) + 23H (aq) →3HClO (aq) + 4Cr (aq) + 10H O(l) − 4 2− + 2 3+ 2 Cl− What is the behaviour (aq)?
    • A. An acid
    • B. A base
    • C. An oxidizing agent
    • D. A reducing agent
    Answer, explanation and textbook page: open in the app.
  65. 66.Based on the following information (KJ) -286 414 -425 What will be the standard enthalpy changes for the reaction? ?
    • A. -978KJ
    • B. -722KJ
    • C. -150KJ
    • D. +275KJ
    Answer, explanation and textbook page: open in the app.
  66. 67.At what condition(s) is the equation, , applicable?
    • A. For constant pressure and temperature processes
    • B. Only for constant pressure processes
    • C. Only for constant temperature processes
    • D. Only for constant volume processes
    Answer, explanation and textbook page: open in the app.
  67. 68.What is a thermodynamic system that exchanges both energy and matter with the surroundings?
    • A. Adiabatic
    • B. Closed
    • C. Isolated
    • D. Open
    Answer, explanation and textbook page: open in the app.
  68. 69.Use the following equilibrium reaction for questions 81 What is the equilibrium expression? (M) 2[CO] K = h [C] [O ] 2 2 [CO]2
    • B. K = 2[C] + [O ] 2 K = [O ] 2 2[CO] K = [O ] 2 [CO]2
    Answer, explanation and textbook page: open in the app.
Other Chemistry years: 2018 2017 2016 2015 2014 2013 2012 2011 2010 2008 2007 2006 2005