U.S. National Chemistry Olympiad: 1989 National Test

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1. Gallium reacts with element Y to form a compound with the formula GaY. If barium were to combine with element Y, the formula of the product would most likely be

(A) BaY
(B) Ba₂Y
(C) Ba₂Y₃
(D) Ba₃Y₂

2. The number of significant figures one can assume in the atomic weight of ¹²C is

(A) 2
(B) 3
(C) 4
(D) unlimited

3. A compound X₂O₃ contains 31.58% oxygen by weight. The atomic weight of X is

(A) 34.66 g/mol.
(B) 45.01 g/mol.
(C) 52.00 g/mol.
(D) 104.0 g/mol.

4. The emission spectrum of the hydrogen atom

(A) is caused by the removal (ionization) of the electron.
(B) is continuous because the electron can emit any frequency of light during a transition.
(C) is caused by the absorption of light at characteristic frequencies the electron to be excited into higher energy levels.
(D) is a result of the excited electron undergoing transitions to lower energy levels and emitting photons of light at specific frequencies.

5. Cathode rays are

(A) a beam of positively charged particles.
(B) nuclei of helium atoms.
(C) fast-moving neutrons.
(D) streams of electrons.

6. Which atom has the correct ground state electron configuration?

(A) Cl: [Ne]3s¹ 3p⁶
(B) Mo: [Kr]5s¹ 4d⁵
(C) Cu: [Ar]4s² 3d⁸
(D) As: [Ar]4s² 4d¹⁰ 4p³

7. The correct number of unpaired electrons in the ground state of a neutral cobalt atom is:

(A) 1
(B) 2
(C) 3
(D) 4

8. Which electron configuration describes a neutral atom in an excited state?

(A) [Xe] 6s 4f¹⁴ 5d¹⁰ 6p³
(B) [He] 2s¹
(C) [Ne] 3s¹ 3p¹
(D) [Ar] 4s¹ 3d⁵

9. The first ionization potential for S is lower than the first ionization potential for P because

(A) Hund's rule is violated.
(B) ionization potentials decrease across a representative period.
(C) half-filled and filled sets of orbitals are more stable than configurations of one more or fewer electrons.
(D) The statement above is false. The first ionization potential for S is higher than that for P.

10. Which set of quantum numbers describe the most easily-removed electron from a neutral iron atom?

(A) n = 4, l = 0, m = 0, s = -1/2
(B) n = 3, l = 2, m = 0, s = +1/2
(C) n = 3, l = 2, m = -1, s = -1/2
(D) n = 1, l = 0, m = 0, s = -1/2

11. The molecular ion XF₂¯ has three pairs of non bonding electrons around the central atom. The bond angle F-X-F will be closest to

(A) 180°.
(B) 120°.
(C) 109°.
(D) 90°.

12. Which species has a pyramidal structure?

(A) ClO₂
(B) ClO₂¯
(C) ClO₃¯
(D) ClO₄¯

13. Which molecule is polar?

(A) CO₂
(B) SF₆
(C) BCl₃
(D) SF₄

14. Which of the following sets have correctly matched each molecule or ion and its geometry?

	Tetrahedral	Trigonal Pyramidal	T-shaped	Square Planar
(A)	CH4	BCl3	NO3¯	SO42¯
(B)	SO42¯	NF3	ICl3	XeF4
(C)	CH4	NO3¯	GaI3	SnCl4
(D)	CCl4	PF3	ICl3	SF4

15. Which Lewis structure is correct?

16. The Lewis structure for dimethyformamide (a useful solvent) is shown below:

How many C and N atoms are sp³, sp², and sp hybridized?

(A) 4 (sp³), 0 (sp²), 0 (sp)
(B) 3 (sp³), 0 (sp²), 1 (sp)
(C) 3 (sp³), 1 (sp²), 0 (sp)
(D) 2 (sp³), 2 (sp²), 0 (sp)

17. Consider the reaction 2 Al(s) + 3 Cl₂(g) ---> 2 AlCl₃(s). What volume of chlorine at STP reacts with 324 g of aluminum?

(A) 121 L
(B) 134 L
(C) 260 L
(D) 403 L

18. How many liters of H₂(g) at 273 °C and 200 torr can be obtained form the reaction of 500 g of zinc with excess hydrochloric acid?

(A) 5.12 L
(B) 343 L
(C) 650 L
(D) 1300 L

19. What is the concentration of a solution prepared by dissolving 4.20 grams of NaF in 500 grams of water?

(A) 0.00840-molal
(B) 0.00840-molar
(C) 0.200-molal
(D) 0.200-molar

20. 10.24 mL of 0.568 M Al(NO₃)₃ is mixed with 3.12 mL, of 4.16 M NaOH. How much solid Al(OH)₃ could be formed?

(A) 0.055 g
(B) 0.075 g
(C) 0.111 g
(D) 0.166 g

21. The standard heat of formation of ammonia gas is -46.1 kJ mol¯¹. How much heat will be produced when 3.04 gram of N₂ reacts with 6.04 g of H₂?

(A) 5.00 kJ
(B) 10.00 kJ
(C) 92.1 kJ
(D) 185.3 kJ

22. At 25 °C and 1 atm, the densities of neon and krypton are 0.82 and 3.42 grams/liter, respectively. The density of argon at the same temperature and pressure is estimated to be

(A) 2.12 g/L
(B) 2.60 g/L
(C) 2.80 g/L
(D) 4.17 g/L

23. When the hydrocarbon propane is burned in air, carbon dioxide and water are formed as in the equation

C₃H₈(g) + 5 O₂(g) ---> 3 CO₂(g) + 4 H₂O(l)

If 0.100 mol of CO₂ is produced, how many drops of water will be formed, assuming one drop is 0.05 cm³ and contains 1.70 x 10²¹ water molecules?

(A) 2.21 x 10¯¹
(B) 0.133
(C) 26.6
(D) 47.2

24. According to the kinetic molecular theory of gases, the Kelvin temperature of a gas is directly proportional to

(A) the average velocity of the gas molecules.
(B) the square of the mass of the gas molecules.
(C) the average kinetic energy of the gas molecules.
(D) the square root of the average velocity of the gas molecules

25. Which is the most viscous at 20 °C and 1.00 atm?

(A) acetone
(B) hexane
(C) tetramethylsilane
(D) water

26. In the van der Waals equation given below,

[P + a (n/V)²] (V - nb) = nRT,

the a(n/V)² and - nb terms represent, respectively, corrections for

(A) derivations in the pressure and the temperature.
(B) intermolecular attractive forces and inelastic collisions.
(C) intermolecular attractive forces and molecular volumes
(D) intermolecular repulsive forces and high temperatures.

27. The Bragg equation yields

(A) rates of flow of liquids.
(B) interatiomic distances in crystals
(C) trajectories of electron beams
(D) frequencies of spectral lines.

28. The empirical formula for a compound with a cubic close-packed arrangement of anions and with cations occupying the octahedral sites is

(A) AB
(B) A₂B
(C) AB₂
(D) AB₃

29. The structure of ice is best described as

(A) a solid network of covalently bounded atoms.
(B) cubic-close packed with 74% of the available sites occupied.
(C) an open structure because of elaborate hydrogen bonding
(D) a flickering cluster of molecules in which protons are easily transferred through the lattice.

30. The structure of glass is best described as

(A) crystalline
(B) fluid
(C) amorphous
(D) close-packed

31. Which solution has the lowest freezing point?

(A) 1.0 molal FeCl₃
(B) 1.0 molal HCl
(C) 1.0 molal KCl
(D) 1.0 molal MgCl₂

32. An aqueous solution is 1.00 molal in KI. Which change will cause the vapor pressure of the solution to increase?

(A) addition of water
(B) addition of NaCl
(C) addition of Na₂SO₄
(D) addition of 1.00 molal KI.

33. Find the boiling point of a solution of 5.00g of naphthalene (C₁₀H₈) in 100 g of benzene. K_b of benzene is 2.53 °C / m; the normal b.p. of benzene = 80 °C.

(A) 0.99 °C
(B) 79 °C
(C) 81 °C
(D) 85 °C

34. What is the degree of ionization of the acid HB if a 0.120 molal solution of HB freezes at -0.300 °C? K_f for water = 1.86 °C / m.

(A) 1.3%
(B) 6%
(C) 21%
(D) 34%

35. Given the standard enthalpies of formation : CO (g), -110.5 KJ/mol; CO₂(g), -393.5 KJ/mol. The enthalpy change for the reaction

2CO(g) + 2 CO₂ (g) --> 4 C(s) + 3 O₂ (g)

is

(A) -1008 kJ
(B) -566 kJ
(C) -504 kJ
(D) +1008 kJ

36. If DH° of vaporization for a liquid is 10.0 kJ / mol and DS° of vaporization is 37.6 J / mol-K, which is the nearest to the normal boiling point of the liquid?

(A) 240 K
(B) 266 K
(C) 300 K
(D) 310 K

37. A reaction has positive values of both DS° and DH°. From this you can deduce that the reaction

(A) must be spontaneous at any temperature.
(B) cannot be spontaneous at any temperature.
(C) will be spontaneous only at low temperatures.
(D) will be spontaneous only at high temperatures.

38. When NH₄NO₃ dissolves in water, the solution becomes cold. From this you can deduce that the DS° for the process is

(A) negative
(B) zero
(C) positive
(D) undeterminable from the data.

39. The distribution coefficient, K_D, for an organic compound between water and methylene chloride is 3.40. An aqueous solution of the organic compound contains 0.500 g per 100 mL and is extracted with 50.0 mL of methylene chloride. What percentage of the organic compound originally in the water is extracted?

(A) 31.5%
(B) 63.0%
(C) 72.0%
(D) 92.6%

40. Which compound is soluble in 8 M NaOH?

(A) Fe(OH)₃
(B) Al(OH)₃
(C) Mn(OH)₂
(D) Ni(OH)₂

41. Which substance can be used to separate Cu²⁺ from Mg²⁺ in an aqueous solution containing Cu(NO₃)₂ and Mg(NO₃)₂?

(A) HCl
(B) H₂S
(C) HClO₃
(D) H₂SO₄

42. Magnesium fluoride is a slightly soluble salt whose solubility product constant is K_sp = 3.7 x 10¯⁸. What is the approximate solubility of magnesium flouride?

(A) 9.2 x 10¯⁹ M
(B) 1.2 x 10¯⁸ M
(C) 1.4 x 10¯⁴ M
(D) 2.1 x 10¯³ M

43. Al(OH)₃ is an insoluble solid whose K_sp = 1.9 x 10¯³³. What is the maximum concentration of OH¯ which can exist in 0.10 M AlCl₃ solution without causing Al(OH)₃ to precipitate?

(A) 2.7 x 10¯¹¹ M
(B) 1.4 x 10¯¹⁰ M
(C) 8.7 x 10¯⁸ M
(D) 3.1 x 10¯⁷ M

44. MY and NY₃, two nearly insoluble salts, have the same K_sp values of 6.2 x 10¯¹³ at room temperature. Which statement would be true in regard to MY and NY₃?

(A) The molar solubilities of MY and NY₃ in water are identical.
(B) The molar solubility of MY in water is less than that of NY₃.
(C) The salts MY and NY₃ are more soluble in 0.5 M KY than in pure water.
(D) The addition of the salt of KY to solution of MY and NY₃ will have no effect on their solubilities.

45. HCN is a weak acid (K_a = 4.0 x 10¯¹⁰). Which statement is NOT true for an aqueous solution of hydrocyanic acid?

(A) The [H⁺] decreases as solution of HCN are made more dilute.
(B) Its percent dissociation increases as solutions are made more dilute.
(C) In a 0.100 M solution of HCN, the HCN is approximately 6.3% dissociated.
(D) The ionization constant, K_a, varies dramatically over a range of concentrations of HCN.

46. Given a weak monoprotic acid such as HCN at equilibrium in aqueous solution, the addition of a strong acid such as HBr to the solution would cause

(A) no change in the concentration of H⁺ or CN¯.
(B) the concentrations of both HCN and CN¯ concentration to increase.
(C) the HCN concentration to increase and the CN¯ concentration to decrease.
(D) the HCN concentration to decrease and the CN¯ concentration to increase.

47. Which solution has pH value above 7.00?

(A) 0.10 M KCI
(B) 0.10 M NH₄NO₃
(C) 0.10 M KCN
(D) 0.10 M HI

48. Which of the following would you expect to have the strongest conjugate acid?

(A) NH₃
(B) SO₄²¯
(C) PO₄³¯
(D) NH₂¯

49. If weak base has the ionization constant, K_b, Then the value of the ionization constant, K_a, of its conjugate acid is given by

(A) 1/K_b
(B) K_w/K_b
(C) K_b/K_w
(D) K_w/K_a

50. Which mixture is a buffer solution?

(A) 0.10 M HI + 0.10 M KI
(B) 0.10 M KCl + 0.10 M NaCl
(C) 0.10 M NaCN + 0.10 M HCN
(D) 0.10 M NaOH + 0.10 M KOH

51. Ethanol is CH₃CH₂OH. Which species is formed when ethanol acts as a Bronsted base?

(A) CH₃CH₂O¯
(B) CH₃CH₂⁺
(C) CH₃CH₂OH₂⁺
(D) H₃O⁺

52. If molten CaCl₂ is electrolyzed, the anode reaction is

(A) Ca²⁺ + 2e¯ ---> Ca
(B) 2Cl¯ ---> Cl₂ + 2e¯
(C) CaCl₂ ---> Ca + Cl₂
(D) 2H₂O ---> O₂ + 4H⁺ + 4e¯

53. The permnganate ion is an excellent oxidizing agent in aqueous solutions. When the half-reaction

MnO₄¯ + H⁺ + e¯ ---> MnO₂ + H₂O

is balanced, the correct coefficients for the species involved are

(A) 1,4,4,1,2
(B) 1,4,2,1,2
(C) 1,4,3,1,2
(D) 1,4,1,1,2

54. A fuel cell uses H₂(g) and Cl₂(g) to form HCl(aq, 1M). Given the standard electrode potential:

Cl₂(g) + 2e¯ ---> 2Cl¯(aq) ; E° = 1.36 V,

What is the maximum electrical work per mole of HCl produced possible from this cell?

(A) 1.36 J
(B) 131,2 kJ
(C) 262,4 kJ
(D) 96,500 kJ

55. Given the standard electrode potentials:

The equilibrium constant for the process

2Br¯ (aq) + Sn⁴⁺ (aq) ---> Br₂(aq) + Sn²⁺ (aq)

is

(A) 1.19 x 10¯⁴²
(B) 3.02 x 10¯³²
(C) 3.31 x 10³¹
(D) 8.40 x 10⁴¹

56. The rate of the reaction 2NO + Cl₂ ---> 2NOCl is given by the rate equation rate = k[NO]²[Cl₂]. The value of the rate constant can be increased by

(A) increasing the concentration of the NO.
(B) increasing the concentration of the Cl₂.
(C) increasing the temperature.
(D) doing all of these.

57. For a certain reaction the rate law is rate = k[C]^3/2. If the rate of the reaction is 0.020 mol L¯¹ s¯¹ when [C] = 1.0 M, what is the rate when [C] = 0.60 M?

(A) 0.0093 mol L¯¹ s¯¹
(B) 0.012 mol L¯¹ s¯¹
(C) 0.033 mol L¯¹ s¯¹
(D) 0.040 mol L¯¹ s¯¹

58. The rate of the reaction 2A + B ---> Products is consistent with the rate equation rate = k[A][B]. Which reaction mechanism is consistent with this information?

(A)	A + B ---> AB	(slow)
	AB + A ---> Products	(fast)
(B)	A + A ---> A2	(slow)
	A2 + B ---> Products	(fast)
(C)	A + B ---> AB	(fast)
(D)	A + A ---> A2	(fast)
	A2 + B ---> Products	(slow)

59. Starting with three different kinds of amino acids, how many different kinds of tripeptide molecules can be made assuming each amino acid can be used more then once in a molecule if desired?

(A) 3
(B) 6
(C) 9
(D) 27

60. Metallic zinc will not reduce

(A) Cu²⁺
(B) H⁺
(C) Ag⁺
(D) Al³⁺

61. What is the pH of the solution that results when 10.0 mL of 0.10 HF (K_a= 6.7 x 10¯⁴) and 10.0 mL of 0.040 M NaOH are mixed?

(A) 1.0
(B) 1.2
(C) 1.5
(D) 3.0

62. A saturated fat is

(A) a substance containing only carbon dioxide and hydrogen.
(B) a fat containing C=C bonds
(C) a substance in which the fat is at its maximum concentration in a solvent .
(D) the primary constitutent of proteins.

63. The principal used of hydrofluoric acid is

(A) in etching glass.
(B) as a bleaching agent.
(C) as an extremely stong oxidizing agent.
(D) in the preparation of organic fluorine compounds.

64. Important commerical extraction processes as welll as analytical techniques utilize carbon dioxide above its critical temperature. Under theses conditions

(A) carbon dioxide is no longer fluid.
(B) one cannot condense the gas to a separate liquid state by applying pressure.
(C) carbon dioxide is known commonly as dry ice.
(D) carbon dioxide dissociates readily into C and O₂.

65. The amount of copper in a 2.00 gram sample of the mineral cuprite was determined by dissolving the sample in nitric acid (HNO₃) and adding an excess of iodide (I¯) solution to the resultant copper nitrate [Cu(NO₃)₂] solution. The iodine (I₂) liberated required 15.7 mL of 0.200 molar sodium thiosulfate (Na₂S₂O₃) solution to be titrated to an end point. What is the percentage of Cu in the mineral? The essential reactions are:

2Cu²⁺ + 4I¯ ---> 2CuI + I₂

I₂ + 2S₂O₃²¯ ---> S₄O₆²¯ + 2I¯

(A) 5.0%
(B) 10%
(C) 20%
(D) 40%

66. A mixture of n-hexane (C₆H₁₄) gas and O₂ gas was inside the vessel was 340 torr. After ignition by a spark, the mixture reacted completely to form CO gas, CO₂ gas, and steam. The total pressure exerted by the gaseous products in the vessel was then 520 torr when the temperature was restored to 297 °C. Which of the following equations describes the reaction that took place in the vessel?

(A) C₆H₁₄ + 8 O₂ ---> 3 CO + 3 CO₂ + 7 H₂O
(B) C₆H₁₄ + 7 O₂ ---> 5 CO + CO₂ + 7 H₂O
(C) 2 C₆H₁₄ + 17 O₂ ---> 4 CO + 8 CO₂ + 14 H₂O
(D) 2 C₆H₁₄ + 15 O₂ ---> 8 CO + 4 CO₂ + 14 H₂O

67. When conducting analyses of substances that are weak acids by titrating solutions with a standardized strong base, the end-point indicator is chosen so that

(A) its color change occurs around the neutralization pH of 7.00.
(B) its color change occurs when the pH is about the same as the pKa of the weak acid.
(C) its color change occurs at a pH that is more basic than pH = 7.00.
(D) its color change occurs at a pH that is the same as that of the standardized base solution.

68. Given the following standard enthalpies of formation in kJ mol¯¹: CH₄ (g), -74.8; C₂H₂(g), 226,9; C₂H₄(g), 52.6; C₂H₆(g), -84.5; CO₂(g), -393.5; H₂O(l), -285.8. Which hydrocarbon, when burned in an excess of oxygen will give the greatest heat per gram of fuel burned?

(A) CH₄
(B) C₂H₂
(C) C₂H₄
(D) C₂H₆

69. A solution may contain NaOH, Na₂CO₃, NaHCO₃ individually or as any pair of the three analytes. A 25.00 mL aliquot of the solution is treated with a standard solution of HCl. Given the following information, what analyte(s) are present in the solution? Addition of phenolphthalein indicator (pink at pH = 10.0 and colorless at pH =8.3) to the solution gives a pink color. The solution becomes colorless after the methyl purple indictor (green at pH = 5.4 and purple at pH = 4.8) to this solution gives a green color. Addition of an additional 15.30 mL of 0.1000 M HCl causes the solution to become purple in color.

(A) NaOH + NaCO₃
(B) NaCO₃ + NaHCO₃
(C) NaHCO₃
(D) NaOH

70. A student standardizes a solution of HCl versus the primary standard Na₂CO₃. He obtains the following values of the molarity of the HCl: 0.1055, 0.0998, 0.1032, 0.0995, 0.0990. What is the relative standard deviation (RSD) of his data expressed in parts per thousand (ppt)?

(A) 5 ppt
(B) 12 ppt
(C) 24 ppt
(D) 27 ppt

1. (14pts.) A 1.529 gram of unknown ester is hydrolyzed in 50.00 ml of 0.236 M NaOH solution according to the reaction below:

RCO₂R'(l) + Na⁺(aq) + OH¯(aq) --->RCO₂¯(aq) + Na⁺(aq) + R'OH(l)

When the reaction is complete, the excess OH¯ ion remaining in this solution is titrated with a 0.115 M HCl solution. The volume of HCl required in this back-titration is 27.83 ml.

(a) How many moles of HCl are consumed during the back-titration?
(b) How many moles of NaOH reacted with the ester?
(c) Calculate the molar mass of the ester.
(d) If the molar mass of the alcohol is 74 g/mol, calculate the molar mass of the acid which can be obtained by acidifying the final solution.
(e) Write structural formulas for all possible isomers of the alcohol.

2. (10pts.) Three samples of magnesium(II) sulfate hydrate were heated and the following results were obtained.

(A) Calculate the percentage of the water that was originally present in each sample.
(B) What percentage of water should be reprted for the magnesium sulfate hydrate? Why?
(C) How can you tell when you have heated a sample long enough?
(D) calculate the number of moles of water per mole of magnesium sulfate in the hydrate.

3. (14pts.) The pH of a 0.65 M solution of HF is 1.66.

(A) Calculate the ionization constant for HF.
(B) Calculate the pH of the solution which resultss when 15.00 mL of 0.42 M NaOH are added to 25.00 mL of 0.65 M HF.
(C) Calculate the [Ca²⁺] required to initiate the precipitation of CaF₂ in the solution in (b). (K_sp = 3.9 x 10¯¹¹)
(D) Calculate the pH of the solution when 25.00 mL of 0.65 M HF is just neutralized with 0.15 M NaOH.

4. (12pts.) Mixtures of hydrazine (N₂H₄) and dinitrogen tetroxide (N₂O₄) have been used as rocket fuels due to their reaction to form N₂ and H₂O. The enthalpies of formation of these substances are:

(A) Write a balanced chemical equation for the reaction of hydrazine and dinitrogen tetroxide to form nitrogen and water.
(B) Calculate the enthalpy change for the reaction in (a).
(C) Calculate the heat which would be released if 0.0800 moles of N₂H₄ is reacted with a stoichiometric amount of N₂O₄.
(D) If 3.36 grams of N₂ and 2.88 grams of H₂O are produced in the reaction in (c), calculate the temperature to which these gases would be heated if the specific heats of N₂ and H₂O are 1.04 J / g-K and 1.87 J / g-K, repectively. (Assume that the heat released contributes only to increasing the temperature of the gaseous products and not of the container. Assume also that the specific heats of N₂ and H₂O do not vary with temperature.)

5. (16 pts.) Write equations for the following reactions.

(A) Concentrated sodium hydroxide solution is added to solid ammonium chloride.
(B) A solution of potassium bromide is added to a solution of Mercury(I) nitrate.
(C) Titanium(IV) chloride is added to excess water.
(D) Equimolar quantities of chlorine and toluene (methylbenzene) are mixed in the presence of iron(III) chloride in the dark.
(E) Solutions of potassium permanganate and tin(II) chloride are mixed.
(F) Radon-220 decays with the loss of an alpha particle.
(G) Excess sodium hydroxide is added to a solution of aluminum nitrate.
(H) Carbon dioxide is bubbled through a solution of calcium hydroxide.

6. (12 pts.) Account for the following observations:

(A) Calcium exhibits an oxidation state of +2 in virtually all its compounds even though the energy required to remove the second electron from a Ca atom is twice as great as that required to remove the first.
(B) the melting point of MgO is 2800 °C while that of NaF is 993 °C even though the interionic distances are within 10% of one another (2.10 x 10¯⁸ cm for MgO and 2.31 x 10¯⁸ cm for NaF).
(C) The F-E-F bond angles in the compounds ClF₃, NF₃, and BF₃ are 90°, 101° and 120°, respectively.
(D) HF is a stronger acid than NH₃ but a weaker acid than HCl even though the electronegativity of fluorine (4.0) is greater than those of nitrogen and chlorine, which are almost the same (3.1 and 2.9, respectively).

7. (12pts.) The standard reduction potentials for a series of technetium species are:

(A) Identify the reactions whose potentials would be affected by pH change and explain your answer.
(B) Compare the relative oxidizing ability of the TcO₄¯ in its reaction to form the Tc²⁺ ion with that of the MnO₄¯ ion when it forms the Mn²⁺ ion (E° = 1.51 volts). Explain your answer.
(C) Identify the species which would be thermodynamically unstable toward disproportionation and explain your reasoning.
(D) Predict the product formed when technetium metal is added to 1.0 M HCl and explain your reasoning.

8. (10pts.) Metal oxides are often referred to as bases and nonmetal oxides as acids.

(A) Explain why.
(B) Write chemical equations which illustrated the basicity of a metal oxide and the acidity of a nonmetal oxide.
(C) Which oxide is more basic? Cr₂O₃ or CrO₃? Why?
(D) Which oxide is more basic? Al₂O₃ or In₂O₃? Why?