ACS Practice Test 2020 Answers PDF

**Short ACS Practice Test** 1. A certain atom has the symbol ^148^~73~**Px**. What does this symbol tell about an atom of the element? \(A) It has 148 electrons. \(B) It has a valence of 4. \(C) It has 221 protons in the nucleus. \(D) It has 75 neutrons in the nucleus. 2. Which pair of e...

**Short ACS Practice Test** 1. A certain atom has the symbol ^148^~73~**Px**. What does this symbol tell about an atom of the element? \(A) It has 148 electrons. \(B) It has a valence of 4. \(C) It has 221 protons in the nucleus. \(D) It has 75 neutrons in the nucleus. 2. Which pair of elements is most likely to react to form a covalently bonded species? \(A) P and O (B) Ca and O \(C) K and S (D) Zn and C 3. Balance the equation for the reaction, using no fractional coefficients. Cr~2~O~3~ + **?** KOH +**?** O~2~ → **?** K~2~CrO~4~ + **?** H~2~O The coefficient of KOH in the balanced equation is \(A) 2 (B) 4 (C) 6 (D) 8 (E) 10 4. A lithium carbide (Li*x*C*y*) reacts with water as follows: Li*x*C*y* + H~2~O → LiOH + C~2~H~2~ (unbalanced) What is the simplest formula of the carbide? \(A) LiC (B) Li~2~C \(C) LiC~2~ (D) Li~3~C~4~ 5. An *sp* hybridized central atom can be used to describe the bonding in \(A) CH~4~ (B) HCN \(C) H~2~CO (D) OF~2~ 6. Which molecule is polar? \(A) BF~3~ (B) CO~2~ \(C) CF~4~ (D) H~2~S 7. The molecule N~2~ is isoelectronic with \(A) formaldehyde, CH~2~O \(B) cyanide ion, CN-- \(C) hydrogen, H~2~ \(D) water, H~2~O 8. Which isoelectronic ion is the smallest in size? \(A) Al^3+^ (B) Na^+^ \(C) F^--^ (D) O^2--^ 9. The atomic molar mass of a hypothetical element **X** is 100 u. It is found that the 50.0 g of **X** combines with 32.0 g of oxygen. What is the simplest formula for the oxide of **X**? Atomic Molar Mass of O = 16.0 g/mol \(A) **X**~2~O (B) **X**O~2~ \(C) **X**~2~O~3~ (D) **X**O~4~ 10. If a 17.0 g sample of impure nickel metal reacts under standard conditions with 25.0 L of CO to form 6.25 L of Ni(CO)~4~ gas, what is the percentage of Ni in the metal sample? Ni*(s)* + 4CO*(g)* → Ni(CO)~4~*(g)* Ni = 58.7 g/mol Ni(CO)~4~ = 171. g/mol \(A) 24.1% (B) 25.0% \(C) 96.4% (D) 100% 11. What is the order of the boiling points (from lowest to highest) for the hydrogen halides? 12. **Which solid is most soluble in water at 25 ⁰C?** A. **AgNO~3~ (B) CaCO~3~** **(C) PbO (D) ZnS** 13. **Mixing equal volumes of 0.1 M Ca(NO~3~)~2~ and AgF solution results in** A. **No precipitate** B. **AgF precipitate** 14. **What is the oxidation number of Re in Mg(ReO~4~)~2~?** A. **+4 (B) +5** **(C) +6 (D) +7** 15. **What is the coefficient of I~2~(s) when the reaction below is balanced with the smallest whole number coefficients?** **Cr~2~O~7~^2-^(aq) + I^-^ (aq) + H^+^ (aq) I~2~(s) + Cr^3+^ (aq) + H~2~O (l)** A. **2 (B) 3** **(C) 4 (D) 6** 16. **Which of the following sets of quantum numbers correspond to a valence electron in a neutral atom of arsenic?** A. **3, 0, 0, + ½** B. **3, 2, 1, - ½** C. **4, 0, 0, + ½** D. **4, 2, 1, - ½** 17. **Which atom has the largest radius?** A. **Na (B) K** 18. **Which element's electronegativity is closest to that of S?** A. **O (B) P** 19. **Formamide has the structure HC(O)NH~2~. Which atoms in formamide have a trigonal planar geometry?** A. **C only (B) N only** 20. **Which of the following molecules has a dipole moment of zero?** A. **HCN (B) CH~2~Cl~2~** 21. **In the Lewis structure for the selenite ion, SeO~3~^2-^, how many lone pairs are around the central atom?** A. **0 (B) 1** 22. Mg(OH)~2~ in the form of Milk of Magnesia is used to neutralize excess stomach acid (HCl). How many moles of stomach acid can be neutralized by 1.00 g of Mg(OH)~2~? (Mg(OH)~2~ 58.33 g/mol) \(A) 0.0171 (B) 0.0343 \(C) 0.686 (D) 1.25 23. How many electrons are needed in the balanced half reaction for the oxidation of ethanol to acetic acid? C~2~H~5~OH CH~3~COOH \(A) 1 (B) 2 \(C) 3 (D) 4 24. **The energy required to break one mole of hydrogen-hydrogen bond in H~2~ is 436 kJ. What is the longest wavelength of light with sufficient energy to break a single hydrogen-hydrogen bond?** A. **122 nm (B) 132 nm** 25. **Atomic nitrogen has a higher ionization energy than atomic oxygen. This is best explained by** A. **The lower electron --electron repulsion in nitrogen** B. **The greater effective nuclear charge of nitrogen** C. **The fact that the electron ionized in N is from the 2s subshell, while that ionized from O is from the 2p subshell.** D. **The fact that N has an odd number of electrons while O has an even number.** 26. A 25.00 mL sample of 0.1050 M H~2~SO~4~ is titrated with a NaOH solution of unknown concentration. The phenolphthalein endpoint was reached when 17.23 mL of the NaOH solution had been added. What is the concentration of the NaOH? \(A) 0.07617 M (B) 0.1447 M \(C) 0.1524 M (D) 0.3047 M 27. Which liquid has the highest vapor pressure at 25 °C? \(A) butane, C~4~H~10~ \(B) glycerol, C~3~H~5~(OH)~3~ \(C) octane, C~8~H~18~ \(D) propanol, C~3~H~7~OH 28. **Boron carbide, B~4~C, is made by the high temperature reaction of boron oxide with graphite, yielding carbon monoxide as a by-product. What is the total of the smallest coefficients for the reactant and products in the balanced equation?** **B~2~O~3~ + C B~4~C + CO** A. **9 (B) 10** 29. **A compound with 69.41% C, 4.16% H, and 26.42% O has a molar mass of 230 -- 250 g/mol. What is the molecular formula?** A. **C~13~H~9~O~4~ (B) C~14~H~10~O~4~** 30. **Aluminum reacts with sulfur to form aluminum sulfide. If 31.9 g of Al reacted with 72.2 g of S, what is the theoretical yield of aluminum sulfide in grams?** A. **88.8 g (B) 69.7 g** 31. **In the Born-Haber calculation of the lattice enthalpy of LiF from its elements, which process is exothermic?** A. **Dissociation energy of F~2~ (g)** B. **Electron affinity of F (g)** C. **Ionization energy of Li (g)** D. **Sublimation energy of Li (s)** 32. Which species is polar? \(A) CO~2~ (B) SO~2~ \(C) SO~3~ (D) O~2~ 33. **For the transition metal with the electron configuration 1s^2^2s^2^2p^6^3s^3^3p^6^4s^2^3d^6^, how many unpaired electrons are present in its +2 ion in the ground state?** A. **0 (B) 2** 34. **Which atom has the highest first ionization energy?** A. **Al (B) Si** 35. **What is the velocity of an electron that exhibits a de Broglie wavelength of 10.0 nm?** A. **72.7 m/s (B) 270 m/s** 36. **For which pair of species are the radii most similar?** A. **Li and Na (B) Na and Mg** 37. **When arranged in order of increasing bond strength, which order is correct?** A. **O -- O \< S -- S \< O = O \< S = S** B. **O -- O \< S -- S \< S = S \< O = O** C. **S -- S \< O -- O \< O = O \< S = S** D. **S -- S \< O -- O \< S = S \< O = O** 38. In which species does the underlined element have an oxidation number of +2? \(A) [S]O~2~Cl~2~ (B) [Fe](CN)~6~^4-^ \(C) H[N]O~2~ (D) [Ni](CO)~4~ 39. **How many stable resonance structures exist for the oxalate ion, C~2~O~4~^2-^?** A. **2 (B) 3** 40. **What is the geometry of ICl~4~^-^ according to VSEPR?** A. **See-saw (B) square planar** 41. **According to the molecular orbital theory, what is the bond order of the carbon-sulfur bond in CS~2~?** A. **1 (B) 2** 42. **Which of the following molecules have sp^3^ hybridized orbitals on the central atom?** **I. PCl~3~ II. COCl~2~ III. SF~4~** A. **I only** 43. **Which characteristic of an atomic orbital is most closely associated with the magnetic quantum number, m~l~?** A. **size (B) shape** 44. Which transformation is an oxidation? \(A) VO~3~^-^ VO~2~^+^ \(B) CrO~2~^2--^ CrO~4~ \(C) SO~3~ SO~4~^2--^ \(D) NO~3~^--^ NO~2~^-^ 45. \_Sn^2+^(aq) + \_NO~3~^-^(aq) + \_H^+^(aq) \_Sn^4+^(aq) + \_NO(g) + \_H~2~O \(A) 2 (B) 4 \(C) 6 (D) 8 46. **Which set of quantum numbers (n, m~l~, m~s~) is not allowed?** A. **3, 2, 0 (B) 3, 1, -1** 47. **What is the frequency of light with a wavelength of 480 nm?** A. **1.60 x 10^-6^ s^-1^ (B) 6.25 x 10^5^ s^-1^** 48. **A 1.0 g sample of which substance contains the largest number of molecules?** A. **HN~3~ (B) N~2~H~4~** 49. **Sulfur trioxide, SO~3~, is made by oxidizing sulfur dioxide, SO~2~, according to the equation below. If a 16.0 g sample of SO~2~ yields 18.0 g of SO~3~, what is the percent yield?** **2SO~2~ + O~2~ 2SO~3~** A. **70.0% (B) 80.0%** 50. **A solution of magnesium chloride that is 5.10% magnesium by mass has a density of 1.17 g/mL. How many moles of Cl^-^ ions are in 300 mL of the solution?** A. **0.368 (B) 0.627** 51. The boiling points of the halogens, F~2~, Cl~2~, Br~2~ and I~2~, increase in that order. This is best attributed to differences in \(A) covalent bond strengths. \(B) dipole forces. \(C) London dispersion forces. \(D) colligative forces. 52. Which equation represents an oxidation-reduction reaction? **(A)** H~2~SO~4~ + 2NH~3~ → (NH~4~)~2~SO~4~ **(B)** H~2~SO~4~ + Na~2~CO~3~ → Na~2~SO~4~ + H~2~O + CO~2~ **(C)** 2K~2~CrO~4~ + H~2~SO~4~ → K~2~Cr~2~O~7~ + K~2~SO~4~ + H~2~O **(D)** 2H~2~SO~4~ + Cu → CuSO~4~ + 2H~2~O + SO~2~ 53. Which species can form intermolecular hydrogen bonds with other molecules or ions of the same type? **1.** HF **2.** CH~3~F **3.** NH~4~^+^ **(A) 1** only **(B) 3** only **(C) 1** and **3** only **(D) 1**, **2** and **3** 54. Which compound has the highest boiling point? **(A)** CH~3~CH~2~CH~3~ **(B)** CH~3~OCH~2~CH~3~ **(C)** CH~3~(CO)CH~3~ **(D)** CH~3~CH~2~CH~2~OH 55. In which process does the nitrogen undergo oxidation? **(A)** N~2~ 2NH~3~ **(B)** N~2~O~4~ 2NO~2~ **(C)** 2NO~3~^--^ N~2~O~5~ **(D)** NO~2~^--^ NO~3~^--^