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Grade 12 Chemistry national exam, 2015 E.C. (2023 G.C.)
76 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.Which one of the following is a colorless, flammable volatile liquid and miscible with non-polar solvents?
- A. Methane
- B. Methanol
- C. Ethanol
- D. Benzene
Answer: D. The question tests which substance is a volatile liquid that mixes with non-polar solvents. Benzene is a colorless, flammable liquid and mixes with non-polar solvents, so D fits. Methane is a gas; methanol and ethanol are alcohols that mix well with water rather than being the intended non-polar solvent. Textbook: Grade 10, unit 2 · section 2.2. - 2.Which one of the following petroleum products is used as a solvent and in dry cleaning?
- A. Diesel oil
- B. Paraffin wax
- C. Petroleum ether
- D. kerosene
Answer: C. Petroleum ether is a light petroleum product used as a solvent. It is used in dry cleaning, so option C is correct. Diesel oil is mainly a fuel; paraffin wax is a solid wax; kerosene is mainly used as a fuel. Textbook: Grade 10, unit 6 · section 6.5. - 3.Which one of the following is NOT TRUE about laboratory preparation of ethylene by dehydration of ethanol?
- A. The collected ethylene gas in the experiment decolorizes alkaline $\mathrm{KMnO_4}$.
- B. Combustion of ethylene produces a non-luminous flame.
- C. Concentrated sulphuric acid is used as a dehydrating agent.
- D. The collected ethylene gas in the experiment decolorizes $\mathrm{Br_2}$ in $\mathrm{CCl_4}$.
Answer: B. The question tests the properties of ethylene made by removing water from ethanol. B is NOT TRUE because ethylene burns with a luminous, often smoky flame, not a non-luminous flame. A is true because ethylene decolorizes alkaline $\mathrm{KMnO_4}$; C is true because concentrated sulphuric acid removes water; D is true because ethylene decolorizes $\mathrm{Br_2}$ in $\mathrm{CCl_4}$. Textbook: Grade 10, unit 6 · section 6.3. - 4.Which one of the following is an essential nutrient of plants?
- A. Potassium
- B. Sodium
- C. Lead
- D. Aluminum
Answer: A. The key idea is that plants need certain elements as nutrients to grow. Potassium is an essential plant nutrient. Sodium is not essential for most plants, while lead and aluminum are not essential nutrients. Textbook: Grade 10, unit 3 · section 3.5. - 5.In a kinetic experiment, a student placed crystals of iodine in a closed reaction vessel, introduced a given quantity of hydrogen gas, and collected data to calculate the rate of formation of hydrogen iodide. What would be the effect obtained on the rate of the reaction, if the student takes more amount of iodine from that used in the first experiment?
- A. The rate of the reaction will be constant.
- B. The formation of hydrogen iodide will be decreased.
- C. It lowers the rate of the reaction.
- D. It speeds up the rate of the reaction.
Answer: A. For a reaction involving a solid, adding more solid does not raise its concentration in the reaction mixture. If the solid iodine crystals have the same exposed surface, more iodine does not change the reaction rate. B is wrong because the extra iodine does not decrease hydrogen iodide formation. C is wrong because it does not lower the rate. D is wrong because it does not speed up the rate. Textbook: Grade 11, unit 5 · section 5.2.4. - 6.Which of the following CORRECTLY relates the vapor pressure of a liquid with its boiling point? Boiling point is
- A. the temperature at which the kinetic energy of molecules is much less than the intermolecular force.
- B. the temperature at which molecules present in the vapor phase go back to the liquid state.
- C. the temperature at which the vapor pressure becomes equal to the external pressure.
- D. the temperature at which all the three physical state co-exist.
Answer, explanation and textbook page: open in the app. - 7.Consider this equilibrium system: CO (g) + Fe O 4 (s) ⇌ CO O 2 (g) + 3 FeO (s) Which of the following disturbances shift the equilibrium position to the right?
- A. Adding Fe O (s)
- B. Removing FeO (s) 3 4
- C. Removing CO (g)
- D. Removing CO₂ (g)
Answer, explanation and textbook page: open in the app. - 8.Which one of the following resulted from interaction of the atomic orbitals of bonding atoms to produce new electron distribution associated with the entire molecule?
- A. Bohr orbit
- B. Electron orbit
- C. Molecular orbital
- D. Hybrid orbital
Answer, explanation and textbook page: open in the app. - 9.Which one of the following graphs illustrates the rate change in terms of a change in reactant concentration with time?
Answer, explanation and textbook page: open in the app. - 10.The heat change at constant pressure that results when 1 mole of a compound is formed from its elements in their standard states is
- A. standard enthalpy of formation
- B. standard reduction potential
- C. standard enthalpy of reaction
- D. standard entropy of reaction
Answer, explanation and textbook page: open in the app. - 11.What is a redox reaction? It is a reaction in which
- A. an acid and a base neutralize each other.
- B. atoms or ions of two compound exchange bonding partners.
- C. electrons are transferred between species.
- D. two insoluble ions in compounds form an insoluble products.
Answer, explanation and textbook page: open in the app. - 12.Which one of the following explains how electroplating takes place?
- A. Metal is deposited on the anode by reduction of ions in the electrolyte solution.
- B. The cations in the electrolyte are supplied either by the added salt or from oxidation of the anode.
- C. The object to be electroplated either metal or graphite-coated plastic constitutes the anode.
- D. The electrolyte is an aqueous solution of a salt of the plated metal.
Answer, explanation and textbook page: open in the app. - 13.How does the equivalent mass of a base is obtained?
- A. By dividing its number of equivalent by the number of OH - ions furnished by one formula unit of a base.
- B. By multiplying its number of equivalent by the number of OH - ions furnished by one formula unit of a base.
- C. By dividing its molar mass by the number of OH - ions furnished by one formula unit of a base.
- D. By multiplying its molar mass by the number of OH - ions furnished by one formula unit of a base.
Answer, explanation and textbook page: open in the app. - 14.Which one of the following reactions would occur spontaneously in an aqueous solution at 25°C? Assume that the initial concentrations of the dissolved species are all 1.0 M. Half reaction E°(V) Sn 2 + ( aq ) + 2 e - ➝ Sn ( s ) -0.14 Br 2 ( l ) + 2 e - → 2 Br - ( aq ) +1.07 Ag + ( aq ) + e - → Ag ( s ) +0.80 Ni 2+ ( aq ) + 2 e - → Ni ( s ) -0.25 Ca 2+ ( aq ) + 2 e - → Ca ( s ) -2.87 Cd 2+ ( aq ) + 2 e - → Cd ( s ) -0.40 Cu 2+ ( aq ) + e - → Cu + ( aq ) +0.15 Fe 3+ ( aq ) → Fe 2+ ( aq ) +0.77
- A. Ca ( s ) + Cd 2+ ( aq ) → Ca 2+ ( aq ) + Cd ( s )
- B. Cu 2+ ( aq ) + Fe 2+ ( aq ) → Cu + ( aq ) + Fe 3+ ( aq )
- C. 2 Br - ( aq ) + Sn 2+ ( aq ) → Br 2 ( 1 ) + Sn ( s )
- D. 2 Ag ( s ) + Ni 2+ ( aq ) → 2 Ag + ( aq ) + Ni ( s )
Answer, explanation and textbook page: open in the app. - 15.Which one of the following is the main reason for the large difference in dipole-moment between the triatomic molecules water (H₂O) and carbon dioxide (CO₂)?
- A. The bonds in carbon dioxide (CO₂) are directed 180° and bond polarity reinforces each other.
- B. The presence of multiple bonds in carbon dioxide (CO₂) while single bonds in water.
- C. The higher electronegativity difference among atoms in water (H₂O) than in carbon dioxide (CO₂).
- D. The presence of lone pairs of electrons in water (H₂O) partially reinforces bond polarities.
Answer, explanation and textbook page: open in the app. - 16.How many non-bonding pairs of electrons are present in the valence shell of the central atom in $\mathrm{ClF_3}$?
- A. 2
- B. 3
- C. 0
- D. 1
Answer, explanation and textbook page: open in the app. - 17.Which one would be observed in a laboratory activity that is applied on naphthalene?
- A. It is soluble in water.
- B. It shows relatively high melting point.
- C. It conducts electricity in molten state.
- D. It is soluble in benzene.
Answer, explanation and textbook page: open in the app. - 18.Which one of the following statements is CORRECT?
- A. Valence bond model explain molecular shape from the interaction of atomic orbitals.
- B. In Lewis model, electrons repel one another and a pair of bonding electrons lies far apart as possible.
- C. Lewis model predicts the shapes, of molecules based on electron-pair repulsions around a central atom.
- D. Valence bond model simply shows the linkage between atoms and the presence of lone pairs.
Answer, explanation and textbook page: open in the app. - 19.The energy required to completely separate one mole of a solid ionic compound into gaseous ions is a/an
- A. Bond energy
- B. Lattice energy
- C. Chemical potential
- D. Boiling Point
Answer, explanation and textbook page: open in the app. - 20.Which of the properties of solvents WOULD NOT be affected by the formation of a solution with a non-volatile solute?
- A. Freezing Point
- B. Chemical identity
- C. Chemical potential
- D. Boiling Point
Answer, explanation and textbook page: open in the app. - 21.The partial pressure of acetylene, $\mathrm{C_2H_2}$, in a container is 10 atm at $25^\circ\text{C}$. What is the solubility in molarity of $\mathrm{C_2H_2}$, assume that $\mathrm{C_2H_2}$ obeys Henry's law? ($K_H = 1.04\,\text{mol/L atm}$)
- A. 10.4
- B. 104
- C. 0.104
- D. 9.62
Answer, explanation and textbook page: open in the app. - 22.What is the normality of a solution that contains 19.6 g of $\mathrm{H_2SO_4}$ in 20 mL of the solution?
- A. 10
- B. 20
- C. 0.01
- D. 0.02
Answer, explanation and textbook page: open in the app. - 23.Which one of the following is the diagrammatic representation of 35 31 Cl?
Answer, explanation and textbook page: open in the app. - 24.The point in a titration at which the number of moles of OH ions added to a solution is equal to the number of + moles of H ions originally present is
- A. Equivalence point
- B. Triple point
- C. End point
- D. Zero point
Answer, explanation and textbook page: open in the app. - 25.Which of the following statements describes chemical industries? It is
- A. a firm that involves usage of raw material to produce desired products by using chemical reactions and refining methods.
- B. a process in which dissolved solute comes out of solution and forms crystals.
- C. an expression for the chemical composition of a compound in terms of the symbols of the atoms of the elements involved.
- D. an area of chemistry concerned with the speeds, or rates, at which chemical reactions occur.
Answer, explanation and textbook page: open in the app. - 26.What will be the product if phosphorus reacts with excess amount of oxygen?
- A. P 4 O 6
- B. P 4 O 10
- C. H 3 PO 4
- D. H 3 PO 3
Answer, explanation and textbook page: open in the app. - 27.One of the basic differences between metallic conduction and electrolytic conduction is:
- A. The conduction of electricity is due to the movement of ions in metallic conduction while the flow of mobile electrons in electrolytic conduction.
- B. The charge carriers in metals are localized electrons while strongly held ions are in electrolytic conduction.
- C. The charge carriers in metals are cations and anions while mobile electrons are in electrolytic conduction.
- D. The conduction of electricity is due to the movement of ions in an electrolytic conduction while the flow of mobile electrons in metallic conduction.
Answer, explanation and textbook page: open in the app. - 28.Which one of the following gases is released from combustion of a fuel in an industrial machinery causing global warming?
- A. $\mathrm{SO_2}$
- B. $\mathrm{NO}$
- C. $\mathrm{CO_2}$
- D. $\mathrm{CO}$
Answer, explanation and textbook page: open in the app. - 29.The number of digits to the right of the decimal point denotes:
- A. Scientific notation
- B. Conversion factor
- C. Decimal places
- D. Significant figures
Answer, explanation and textbook page: open in the app. - 30.Which one of the following IS TRUE about isotopes?
- A. Isotopes of an element have the same chemical properties.
- B. Isotopes of the same elements contain the same number of neutrons.
- C. Isotopes of an element are identical in mass number.
- D. Isotopes of an element are atoms that have different number of electrons and protons.
Answer, explanation and textbook page: open in the app. - 31.Which one of the following describes the quantum mechanical model?
- A. Electrons moved around the nucleus of an atom in circular orbits.
- B. An atom is a sphere with a positively charged matter, in which electrons are embedded.
- C. An atom is represented by a solid indestructible sphere.
- D. The locations of electrons in an atom are described in terms of probability.
Answer, explanation and textbook page: open in the app. - 32.Which one of the following is an ionic compound?
- A. $\mathrm{H_2O_2}$
- B. $\mathrm{PCl_3}$
- C. $\mathrm{CO_2}$
- D. $\mathrm{CaCl_2}$
Answer, explanation and textbook page: open in the app. - 33.An element is located in Group VIIA and 3 period of the modern periodic table. On the basis of this the element;
- A. has extremely low electron affinity.
- B. forms an acidic oxide.
- C. has very low ionization energy.
- D. generally forms an ion with -2 charges.
Answer, explanation and textbook page: open in the app. - 34.Which one of the following is the reducing agent in the following reaction? $8\mathrm{NH_3(g)}+6\mathrm{NO_2(g)}\to7\mathrm{N_2(g)}+12\mathrm{H_2O(l)}$
- A. $\mathrm{N_2}$
- B. $\mathrm{H_2O}$
- C. $\mathrm{NH_3}$
- D. $\mathrm{NO_2}$
Answer, explanation and textbook page: open in the app. - 35.Carbon forms two stable compounds with oxygen, namely, carbon monoxide and carbon dioxide. For a fixed mass of carbon, the ratio of oxygen in carbon monoxide to oxygen in carbon dioxide is 1:2. This result is consistent with the law of
- A. multiple proportion.
- B. constant composition.
- C. conservation of mass.
- D. definite proportion.
Answer, explanation and textbook page: open in the app. - 36.When a system at equilibrium is disturbed by a change of variable, the system shifts the equilibrium position in a way that tends to counteract this change of variable. This is a statement for
- A. Le Chatelier Principle
- B. Heisenberg uncertainty principle
- C. Aufbau principle
- D. Pauli's exclusion principle
Answer, explanation and textbook page: open in the app. - 37.Which one of the following gas laws states the volume of a fixed amount of gas maintained at constant pressure is directly proportional to the absolute temperature of the gas?
- A. Combined gas law
- B. Avogadro's law
- C. Boyle's law
- D. Charles' law
Answer, explanation and textbook page: open in the app. - 38.Which one of the following is an example of molecular crystals?
- A. Magnesium
- B. Solid carbon dioxide
- C. Sodium Chloride
- D. Diamond
Answer, explanation and textbook page: open in the app. - 39.Which one of the following COULD NOT be considered as factor influencing the rate of chemical reaction?
- A. Temperature of reactants
- B. The rate constant of the reaction
- C. Surface area of reactants
- D. Presence of catalyst
Answer, explanation and textbook page: open in the app. - 40.In which of the following order of a reaction, a plot of $\ln [A]_t$ versus time is a straight line whose slope is $-k$?
- A. Second
- B. Third
- C. Zero
- D. First
Answer, explanation and textbook page: open in the app. - 41.A forward and reverse reaction continues to take place at equal rate in microscopic level without change in composition at macroscopic level. This statement is the definition of
- A. The law of mass action
- B. Degree of freedom
- C. Dynamic equilibrium
- D. Chemical kinetics
Answer, explanation and textbook page: open in the app. - 42.What are the four quantum numbers for an electron in a 2s orbital?
- A. 2,0,1,+½
- B. 2,0,0,+½
- C. 2,1,1,+½
- D. 2,1,0,+½
Answer, explanation and textbook page: open in the app. - 43.A student uses a digital balance (±0.02), a thermometer (±0.1), a measuring cylinder (±0.05), and a beaker (±0.5) during an experiment. Which of the above instrument is more precise?
- A. The measuring cylinder
- B. The Beaker
- C. The digital balance
- D. The thermometer
Answer, explanation and textbook page: open in the app. - 44.Which one of the following explains that light has BOTH wave and particle nature?
- A. Light consists of electromagnetic waves which have an oscillating electric and magnetic disturbance that spreads electromagnetic radiation.
- B. Microscopic systems, such as atoms and molecules can possess wave properties.
- C. An electron that is bound to the nucleus behaves like a standing wave and its position is given in terms of probability.
- D. A beam of light is a stream of particles of electromagnetic energy, with energy proportional to the observed frequency of the light.
Answer, explanation and textbook page: open in the app. - 45.A nuclear breakdown in which particles or electromagnetic radiation is emitted is _______________.
- A. Radioactive decay
- B. Radio wave
- C. Radioactivity
- D. Radioactive isotopes
Answer, explanation and textbook page: open in the app. - 46.Which statement describes valence shell electron pair repulsion (VSEPR) theory?
- A. A covalent bond is formed when orbitals of two atoms overlap and the overlap region is occupied by a pair of electrons.
- B. Atomic orbitals are capable of combining to produce new electron distribution.
- C. Electron pairs will be as far apart from each other in three dimensional spaces as possible.
- D. Each degenerate orbitals are occupied by a single electron before the second electrons of opposite spin enters the orbitals.
Answer, explanation and textbook page: open in the app. - 47.Which of the following compounds reacts with basic oxide to form salt and water?
- A. Neutral oxide
- B. Base
- C. Acidic oxide
- D. Acid
Answer, explanation and textbook page: open in the app. - 48.Which one of the following reaction represents formation of an acid from its salt?
- A. AgNO 3 ( aq ) + NaCl ( aq ) → NaNO 3 ( aq ) + AgCl ( s )
- B. NaNO 3 ( s ) + H 2 SO 4 ( l ) → NaHSO 4 ( s ) + HNO 3 ( l )
- C. P 2 O 5 ( s ) + 6 NaOH ( aq ) → 2 Na 3 PO 4 ( s ) + 3 H 2 O ( l )
- D. CH 3 COOH ( aq ) + CH 3 OH ( aq ) → CH 3 CO 2 CH 3 ( aq ) + H 2 O ( l )
Answer, explanation and textbook page: open in the app. - 49.The negative logarithm of the molar concentration of hydrogen ion to the base ten is known as ____________.
- A. pOH
- B. $K_a$
- C. $K_w$
- D. pH
Answer, explanation and textbook page: open in the app. - 50.Which one of the following galvanic cell is an example of secondary cell?
- A. Zinc-carbon dry cell
- B. Leclanche dry cell
- C. Lead storage cell
- D. Daniel's cell
Answer, explanation and textbook page: open in the app. - 51.Which one of the following is responsible for electrolytic conductivity?
- A. Movement of ions.
- B. Electrons held in a fixed position.
- C. Free electrons.
- D. Ions strongly held in a fixed position.
Answer, explanation and textbook page: open in the app. - 52.The pH of a 0.1 M solution of formic acid (HCOOH) is 3. What is the Ka of the acid? −5 −4
- A. 9.99 x 10
- B. 9.99 x 10 −7 −5
- C. 1.01 x 10
- D. 1.01 x 10
Answer, explanation and textbook page: open in the app. - 53.A system does 15 J of work and no other changes take place. Which of the following function has fallen by 15 J?
- A. Entropy
- B. Enthalpy
- C. Specific heat
- D. Internal energy
Answer, explanation and textbook page: open in the app. - 54.Which of the following is CORRECTLY stated about the spontaneity of a reaction?
- A. For an exothermic reaction with negative reaction entropy, the reaction is spontaneous at high temperature.
- B. For an endothermic reaction with positive reaction entropy, the reaction is non-spontaneous at low temperature.
- C. For an exothermic reaction with positive reaction entropy, the reaction is non-spontaneous at all temperature.
- D. For an endothermic reaction with negative reaction entropy, the reaction is spontaneous at all temperature.
Answer, explanation and textbook page: open in the app. - 55.In thermodynamics: solutions in a beaker, a gas in a cylinder, a reaction vessel, a biological cell are examples of a
- A. thermodynamic system
- B. path function
- C. state function
- D. thermodynamic variables
Answer, explanation and textbook page: open in the app. - 56.Given the following: bond energies (kJ/mol) H-H 936 N-N 193 N=N 409 N≡N 942 and the enthalpy for the reaction 1 2 N 2 ( g ) + 3 2 H 2 ( g ) → NH 3 ( g ) ; ΔH = -45 kJ/mol What is the bond energy for NH ? 3
- A. 1080
- B. 960
- C. 1170
- D. 1125
Answer, explanation and textbook page: open in the app. - 57.Which of the following would occur during the formation of ions?
- A. Valence electrons are transferred from one atom to another.
- B. The electronic configuration of an atom forming the ion remains unaffected.
- C. Valence electrons are shared between atoms.
- D. Inner most shell electrons are involved.
Answer, explanation and textbook page: open in the app. - 58.In order to illustrate the structure and properties of a solid, a student put hundred marble balls in to a box that representing metal cations and the empty space between and around the marble representing the electron sea. Which one of the following bonding is represented by this model?
- A. Dative bonding
- B. Metallic bonding
- C. Ionic bonding
- D. Covalent bonding
Answer, explanation and textbook page: open in the app. - 59.Which one of the following explains dipole-dipole force?
- A. An electrostatic attraction between metal ions and valence electrons.
- B. An attractive force resulting from temporary dipoles induced in molecules.
- C. The intermolecular attraction between oppositely charged poles of nearby polar molecules.
- D. A type of intermolecular force that exists between non- polar molecules.
Answer, explanation and textbook page: open in the app. - 60.Which one of the following reactions creates energy in our bodies during respiration?
- A. N 2 H 4 CO ( g ) + H 2 O ( g ) → 2 NH 3 ( l ) + CO 2 ( g )
- B. C 6 H 12 O 6 ( s ) → 2 C 2 H 5 OH ( l ) + 2 CO 2 ( g )
- C. 6 CO 2 ( g ) + 6 H 2 O ( l ) → C 6 H 12 O 6 ( s ) + 6 O 2 ( g )
- D. C 6 H 12 O 6 ( s ) + 6 O 2 ( g ) → 6 CO 2 ( g ) + 6 H 2 O ( l )
Answer, explanation and textbook page: open in the app. - 61."A reaction that involves the exchange of positive and negative ions of each reactant". This is a definition of a
- A. Single displacement reaction
- B. Double displacement reaction
- C. Combination reaction
- D. Decomposition reaction
Answer, explanation and textbook page: open in the app. - 62.Which one of the following statement is TRUE about gases?
- A. The volume of a gas is equal to the volume of its container.
- B. When a gas sample is heated at constant pressure, its volume decreases.
- C. The volume of a gas is kept constant as pressure increases.
- D. The particles of gases are closely packed together.
Answer, explanation and textbook page: open in the app. - 63.Which one of the following mathematical expressions is derived from the combination of Boyle's law, Charles' law and Avogadro's law?
- A. V α ( P n T )
- B. V α ( nP T )
- C. V α ( T nP )
- D. V α ( nT P )
Answer, explanation and textbook page: open in the app. - 64.180 g of calcium carbonate ($\mathrm{CaCO_3}$) is allowed to react with 156 gram of hydrochloric acid ($\mathrm{HCl}$), according to the following reaction. Which of the following substances is the limiting reagent? (Atomic masses; Ca=40, Cl 35.5, O=16, C=12, H=1) $\mathrm{CaCO_3}+2\ \mathrm{HCl}\rightarrow\mathrm{CaCl_2}+\mathrm{CO_2}+\mathrm{H_2O}$
- A. $\mathrm{CO_2}$
- B. $\mathrm{H_2O}$
- C. $\mathrm{CaCO_3}$
- D. $\mathrm{HCl}$
Answer, explanation and textbook page: open in the app. - 65.Which one of the following isomers differs in the arrangement of carbon atoms in the longest continuous carbon chain?
- A. Structural
- B. Cis-trans
- C. Position
- D. Geometric
Answer, explanation and textbook page: open in the app. - 66.Which one of the following methods can be used in the laboratory for the preparation of alkynes?
- A. Hydrogenation of alkenes with a metal catalyst.
- B. Dehydrohalogenation of adjacent dihalides with sodium hydroxide.
- C. Heating of sodium salt of an organic acid with soda lime.
- D. Dehydration of alcohols with concentrated sulphuric acid.
Answer, explanation and textbook page: open in the app. - 67.Which one of the following is TRUE about the electrolysis of a molten hypothetical electrolyte, MX?
- A. The overall reaction is redox reaction.
- B. Electrons are not transferred from one species to the other.
- C. M is produced at the anode.
- D. X is produced at the negative electrode.
Answer, explanation and textbook page: open in the app. - 68.During the extraction of an unknown metal, the metallic ore was fused with NaOH in air and then dissolved in water to obtain the soluble unknown metal containing species. Reduction with carbon is followed after the solution is treated with HCl. Finally the obtained oxide is reduced to its metallic form by aluminum. The most probable unknown metal would be
- A. Pb
- B. Cr
- C. Zn
- D. Ca
Answer, explanation and textbook page: open in the app. - 69.Why tin does NOT react with cold water but calcium reacts with cold water quite readily?
- A. Due to the pH of water.
- B. Due to its physical state.
- C. Due to the formation of a thin oxide layer.
- D. Due to its less reactive nature.
Answer, explanation and textbook page: open in the app. - 70.Why is vulcanization performed in natural rubber?
- A. To increase the number of monomer unit in the natural rubber.
- B. To decrease the number of monomer unit in the natural rubber.
- C. To establish cross-links between polymer chain in the natural rubber.
- D. To convert the monomer unit in natural rubber in to polymer.
Answer, explanation and textbook page: open in the app. - 71.Which one of the following explains the determination of the cell potential of Zn-Cu cell using voltmeter?
- A. After the experiment the mass of zinc is increased.
- B. Each U-tube served as a salt bridge that can be filled with saturated KCI.
- C. In the Zn half- cell, Zn metal will be dipped in CuSO solution. 4
- D. In the Cu half-cell, Cu metal will be dipped in ZnSO solution. 4
Answer, explanation and textbook page: open in the app. - 72.The rate law for: is rate= . The accepted mechanism for the reaction is Why DOES NOT H O appear in the rate 2 law? Beacuse
- A. water is missing in the rate determining step.
- B. water exists in the liquid state in the reaction.
- C. water is an intermediate species.
- D. water is a catalyst in the reaction.
Answer, explanation and textbook page: open in the app. - 73.Which type of substances has the following general formula? (R , R and R hydrocarbon groups.) 1 2 3
- A. Fatty acids
- B. Alcohols
- C. Fats
- D. Carboxylic acids
Answer, explanation and textbook page: open in the app. - 74.The rate law for this reaction CO ( g ) + NO 2 ( g ) → CO 2 ( g ) + NO ( g ) is rate = k [NO ] . Which one of the following could be a plausible mechanism for the reaction?
- A. NO 2 ( g ) + NO 2 ( g ) → NO 3 ( g ) + NO 2 ( g ) [fast] NO 3 ( g ) + CO ( g ) → NO 2 ( g ) + CO 2 ( g ) [slow]
- B. NO 3 ( g ) + NO ( g ) → NO 2 ( g ) + NO 2 ( g ) [slow] NO 2 ( g ) + CO 2 ( g ) → NO 3 ( g ) + CO 2 ( g ) [fast]
- C. NO 3 ( g ) + NO ( g ) → NO 2 ( g ) + NO 2 ( g ) [slow] NO 3 ( g ) + CO ( g ) → NO 2 ( g ) + CO 2 ( g ) [fast]
- D. NO 2 ( g ) + NO 2 ( g ) → NO 3 ( g ) + NO ( g ) [slow] NO 3 ( g ) + CO ( g ) → NO 2 ( g ) + CO 2 ( g ) [fast]
Answer, explanation and textbook page: open in the app. - 75.The speed with which a solute goes into solution is
- A. extent of dissolution
- B. rate of dissolution
- C. heat of solution
- D. degree of solvation
Answer, explanation and textbook page: open in the app. - 76.Which one of the following explains how 2 L of 1 M NaOH aqueous stock solution is converted into a 0.25 M NaOH solution?
- A. Evaporating 1 L of water from the stock solution
- B. Evaporating 0.25 L of water from the stock solution
- C. Adding 8 L water to the stock solution
- D. Adding 6 L water to the stock solution
Answer, explanation and textbook page: open in the app.