1. Glyoxal consists of 41.4% C, 3.5% H, and 55.1% O by mass. What is the empirical formula of glyoxal? (A) CHO (B) CH 2 O (C) CH 2 O 2 (D) C 12 HO 16

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1 1 ACS Final Review **Questions are taken from actual past ACS USNCO exams. It is an overview of the topics that will be covered on the exam based on `materials covered. Please continue to study and review the materials on your own as well. 1. Glyoxal consists of 41.4% C, 3.5% H, and 55.1% O by mass. What is the empirical formula of glyoxal? (A) CHO (B) CH 2 O (C) CH 2 O 2 (D) C 12 HO How many hydroxide ions are in 2.5 mol Mg(OH) 2? (A) (B) (C) (D) In a sample consisting of 1.00 mol NaBr and mol KI, what is the mass percent of iodine? (A) 24.9% (B) 32.6% (C) 47.2% (D) 83.1% 4. Barium chloride reacts with sodium sulfate according to the following equation: BaCl 2 (aq) + Na 2 SO 4 (aq) BaSO 4 (s) + 2 NaCl(aq) A student mixes a solution containing 10.0 g BaCl 2 (M = 208.2) with a solution containing 10.0 g Na 2 SO 4 (M = 142.1) and obtains 12.0 g BaSO 4 (M = 233.2). What is the percent yield of this reaction?

2 2 (A) 60.0% (B) 73.1% (C) 93.3% (D) The isolated barium sulfate is most likely wet, since the yield would otherwise be greater than 100% A white ionic solid is dissolved in water. Addition of a solution of sodium chloride to this solution results in a white precipitate. What was the cation in the original ionic solid? (A) Na + (B) Fe 3+ (C) Ag + (D) Sr A 0.1 M solution of which salt is the most basic? (A) NaNO 3 (B) NaClO 4 (C) NaHSO 4 (D) NaHCO 3 7. A sample of neon gas is held at 25.0 o C and 1.0 atm in a cylinder with a movable piston. Under these conditions the gas occupies 5.0 L. What volume does the gas occupy at 12.5 oc and 1.0 atm? (A) 2.5L (B) 4.8L (C) 5.2L (D) 10L 8. A sample of 54.0 g of methanol is heated from 25.0 C to 35.0 C. How much heat is required? The specific heat capacity of methanol is 2.48 J g 1 K 1. (A) J (B) J (C) 1340 J (D) 4690 J

3 3 9. Given the standard enthalpy changes for the reactions: P 4 (s) + 3 O 2 (g) P 4 O 6 (s) ΔHo = 1640 kj mol 1 P 4 (s) + 5 O 2 (g) P 4 O 10 (s) ΔHo = 2940 kj mol 1 Calculate the standard enthalpy change Ho for the following reaction: P 4 O 6 (s) + 2 O 2 (g) P 4 O 10 (s) (A) kj mol 1 (B) kj mol 1 (C) 1.79 kj mol 1 (D) kj mol How many total orbitals are there with principal quantum number n = 4? (A) 1 (B) 4 (C) 9 (D) The wavelength of one of the spectral lines of helium is 492 nm. What is the energy of a photon with this wavelength? (A) J (B) J (C) J (D) J 12. What is the formal charge on the central nitrogen in the Lewis structure of N 2 O? (A) 0

4 4 (B) +1 (C) 1 (D) 0 in some resonance structures, 1 in other resonance structures Shown below is a Lewis structure of the formamidinium ion. What geometry is exhibited by the two nitrogens in the formamidinium ion? (A) J (C) J (B) J (D) J 13. Which of the following gas-phase ions has the largest number of unpaired electrons in its ground state? (A) Cr 3+ (B) Co 3+ (C) Ni 2+ (D) Cu Shown below is a Lewis structure of the formamidinium ion. What geometry is exhibited by the two nitrogens in the formamidinium ion? Geometry at A (A) trigonal planar (B) trigonal planar (C) trigonal pyramidal (D) trigonal pyramidal Geometry at B trigonal planar trigonal pyramidal trigonal planar trigonal pyramidal

5 5 15. What is the geometry of SF 4? (A) Tetrahedral (B) Square planar (C) See-saw (D) Trigonal monopyramidal 16. How many s and π bonds are in 1,3-butadiene, H 2 C=CH CH=CH 2? (A) 7sand2pbonds (B) 2sand7pbonds (C) 9sand2pbonds (D) 2sand9pbonds 17. A 20.0 g sample of mercury(ii) oxide (HgO, M = 216.6) is heated strongly, causing it to decompose to metallic Hg and O 2 gas. What volume of O 2 gas is produced (measured at STP)? (A) 1.03 L (B) 2.07 L (C) 4.14 L (D) 14.0 L 18. When 30.0 ml of 0.10 M AgNO 3 is added to 30.0 ml of 0.10 M NaCl, aqueous NaNO 3 and solid AgCl are formed. How much solid AgCl is produced? (A) mol (B) mol (C) mol (D) mol 19. How much Sr(OH) 2 8 H 2 O (M = ) is needed to prepare ml of solution in which [OH ] = M? (A) 3.32 g (B) 6.64 g (C) 9.97 g (D) 13.3 g 20. A g sample of a compound containing only carbon, hydrogen, and oxygen forms g CO 2 and 4.91 g H 2 O upon complete combustion. What is the empirical formula of the compound? (A) C 2 HO (B) C 3 H 3 O (C) C 6 H 3 O 2 (D) C 6 H 6 O 21. Which of the following is a nonelectrolyte in aqueous solution? (A) H 2 SO 4 (B) NaC 2 H 3 O 2 (C) K 2 CO 3 (D) CH 2 O

6 ml of M aqueous NaOH is added to ml of M aqueous NaHCO 3 in a flask maintained at 25 ºC. Neglecting the effects of dilution, what is q for this reaction? Hº f, kj mol 1 OH (aq) 230 HCO 3 (aq) 692 CO 3 2 (aq) 677 H 2 O(l) 286 (A) 41 J (B) 74 J (C) 330 J (D) 820 J 22. In a well-insulated vessel, 50.0 g ice at 0.0 ºC is added to 350. g water at 32.0 ºC. What is the final temperature when the mixture reaches equilibrium? (The heat of fusion of ice is 334 J g 1.) (A) 18.0 ºC (B) 20.6 ºC (C) 22.0 ºC (D) 28.0 ºC 23. The bond dissociation enthalpies of the H H bond and the H Cl bond are 435 kj mol 1 and 431 kj mol 1, respectively. The Hº f of HCl(g) is 92 kj mol 1. What is the bond dissociation enthalpy of the Cl Cl bond? (A) 88 kj mol 1 (B) 96 kj mol 1 (C) 188 kj mol 1 (D) 243 kj mol Which statement about chemical reaction mechanisms is correct? A. The overall rate law can be determined from any step in the mechanism. B. The rate of a reaction is the rate of the fastest elementary step of its mechanism. C. The chemical equation for the sum of all the elementary steps is the chemical equation of the overall reaction. D. Species that are produced and subsequently consumed in the mechanism serve as catalysts for the reaction. 25. When the equation ClO 2 (aq) + OH (aq) ClO 2 (aq) + ClO 3 (aq) + H 2 O(l) is balanced, what is the ratio of the coefficient of ClO 2 to that of ClO 3? (A) 1 : 1 (B) 2 : 1 (C) 3 : 1 (D) 3 : 2

7 7 26. Which of the following statements is best supported by the data from Rutherford s experiment of scattering alpha particles with a thin metal foil? A. The mass and positive charge of an atom are concentrated in its center. B. Electrons in atoms occupy only certain specific energy levels. C. Moving particles can also be described as waves. D. Atoms of a given element do not all have identical masses. 27. As atomic number increases from 11 to 15, the atomic radii of the elements (A) increase (B) decrease (C) increase, then decrease (D) decrease, then increase 28. Nitrogen has a greater first ionization energy than oxygen. What is the best explanation for this observation? E. Nitrogen is more electronegative than oxygen. F. A nitrogen atom is smaller than an oxygen atom. G. The electron ionized from nitrogen experiences less electron-electron repulsion than the electron ionized from oxygen. H. The electron ionized from nitrogen is a 2s electron, while the electron ionized from oxygen is a 2p electron. 29. Which set of quantum numbers n, l, m l, m s is invalid? (A) 1, 1, 0, ½ (B) 2, 0, 0, +½ (C) 3, 1, 0, +½ (D) 4, 3, 2, ½ 30. Which molecule is nonpolar, yet contains polar covalent bonds? (A) CO 2 (B) HCN (C) NH 3 (D) P The nitrite ion, NO 2, can be represented as a resonance hybrid of two significant Lewis structures. Which statements about this are correct?

8 8 I. The two resonance structures contribute equally to the structure. II. The formal charge of nitrogen is zero in both resonance structures. (A) I only (B) II only (C) Both I and II (D) Neither I nor II 32. What is the molecular geometry of IF 3? (A) Trigonal planar (C) T-shaped (B) Trigonal pyramidal (D) Tetrahedral 33. Which contains sp 3 -hybridized carbon atoms? (B) Benzene, C 6 H 6 (B) Ethane, C 2 H 6 (C) Ethene, C 2 H 4 (D) Ethyne, C 2 H How many sigma bonds are in 2-butyne (CH 3 CºCCH 3 )? (A) 3 (B) 6 (C) 9 (D) 11

9 8B 10 8B 11 1B. 28 Ni Cu Co Ag Pd Rh Ir Pt Au

9 8B 10 8B 11 1B. 28 Ni Cu Co Ag Pd Rh Ir Pt Au 1 PERIODIC TABLE OF THE ELEMENTS 18 1A 8A 1 H 1.008 2 2A 3 3B 4 4B 5 5B 6 6B 7 7B 8 8B 9 8B 10 8B 11 1B 12 2B 13 3A 14 4A 15 5A 16 6A 17 7A 2 He 4.003 3 Li 6.941 4 Be 9.012 5 B 10.81 6 C 12.01 7 N 14.01