ACS Practice Test Welcome to your ACS Practice Test 1. ACS: Atomic structure Which statement about isotopes is correct? Isotopes of an element have different numbers of protons. Isotopes of an element have different numbers of electrons. Isotopes of an element have different numbers of neutrons. Isotopes of an element have different electron configurations. None 2. ACS: Atomic structure Which quantum number determines the shape of an electron orbital? Principal quantum number (n) Azimuthal quantum number (l) Magnetic quantum number (m_l) Spin quantum number (s) None 3. ACS: Atomic structure What is the total number of orbitals in the third energy level (n=3) of an atom? 3 5 9 7 None 4. ACS: Atomic structure Which is the correct electron configuration for the outer shell of a bromine atom in the ground state? 4s^2 4p^5 4s^2 4p^6 3s^2 3p^5 4s^2 3d^10 4p^5 None 5. ACS: Atomic structure The Aufbau principle states that: Electrons occupy the highest energy orbitals first. Electrons pair up in an orbital only after all orbitals in the same sublevel have one electron. Electrons fill the orbitals of lowest energy first. Electrons in the same orbital must have the same spin. None 6. ACS: Atomic structure Which electron configuration is possible for an atom in an excited state? 1s^2 2s^2 2p^6 1s^2 2s^2 2p^5 3s^1 1s^2 2s^2 2p^6 3s^2 1s^2 2s^2 2p^6 3p^1 None 7. ACS: Atomic structure Which electronic transition in a hydrogen atom emits the highest energy photon? n = 2 to n = 1 n = 3 to n = 2 n = 5 to n = 2 n = 4 to n = 3 None 8. ACS: Molecular structure and bonding What type of orbital overlap occurs in the formation of a sigma bond between hydrogen and carbon in methane (CH\(_4\))? s-s s-p p-p d-p None 9. ACS: Molecular structure and bonding Which of the following molecules has resonance structures? CO\(_2\) CH\(_4\) SO\(_2\) H\(_2\)O None 10. ACS: Molecular structure and bonding What best describes the bonding in benzene, C\(_6\)H\(_6\)? Ionic bonding Sigma bonding only Pi bonding only Sigma and delocalized pi bonding None 11. ACS: Molecular structure and bonding Which intermolecular force is primarily responsible for the high boiling point of water compared to hydrogen sulfide? London dispersion forces Dipole-dipole interactions Hydrogen bonding Ionic bonding None 12. ACS: Molecular structure and bonding In terms of molecular polarity, which molecule below is nonpolar despite having polar bonds? Water (H\(_2\)O) Carbon dioxide (CO\(_2\)) Ammonia (NH\(_3\)) Hydrogen sulfide (H\(_2\)S) None 13. ACS: Molecular structure and bonding Which of the following molecules has resonance structures? CO\(_2\) CH\(_4\) SO\(_2\) H\(_2\)O None 14. ACS: Molecular structure and bonding What electronic effect does the nitro group (-NO\(_2\)) have when attached to a benzene ring? Electron-donating by resonance Electron-donating by induction Electron-withdrawing by resonance Electron-withdrawing by induction None 15. ACS: Stoichiometry If 5.0 moles of propane (C3H8) are burned completely in excess oxygen, how many moles of carbon dioxide are produced? 10 moles 15 moles 20 moles 30 moles None 16. ACS: Stoichiometry How many grams of \( \text{Fe}_2\text{O}_3 \) can be formed from the reaction of 8.4 grams of iron with excess oxygen? 12.0 grams 6.0 grams 11.2 grams 8.4 grams None 17. ACS: Stoichiometry What is the limiting reagent when 3.0 grams of \( \text{Al} \) react with 4.0 grams of \( \text{O}_2 \) to form aluminum oxide? \( \text{Al} \) \( \text{O}_2 \) \( \text{Al}_2\text{O}_3 \) Neither None 18. ACS: Stoichiometry What volume of carbon dioxide at STP is produced from the combustion of 100 grams of butane (\( \text{C}_4\text{H}_{10} \))? 134.4 L 268.8 L 336.0 L 672.0 L None 19. ACS: Stoichiometry A mixture of 5.0 grams of \( \text{H}_2 \) and 20.0 grams of \( \text{O}_2 \) is ignited. What is the mass of water vapor formed? 18.0 grams 25.0 grams 22.5 grams 20.0 grams None 20. ACS: Stoichiometry If 7.0 grams of nitrogen reacts with 3.0 grams of hydrogen, how many grams of ammonia are produced? 6.0 grams 8.5 grams 10.0 grams 17.0 grams None 21. ACS: Stoichiometry In the reaction where calcium carbonate decomposes into calcium oxide and carbon dioxide, how much carbon dioxide can be produced from 50 grams of calcium carbonate? 22 grams 44 grams 11 grams 33 grams None 22. ACS: States of matter or solutions In terms of molecular movement, how do gases differ from liquids? Molecules in gases move slower than in liquids. Molecules in gases are more closely packed than in liquids. Molecules in gases move faster and are further apart than in liquids. There is no significant difference in molecular movement. None 23. ACS: States of matter or solutions Which factor does NOT affect the rate of dissolution of a solute in a solvent? Temperature of the solvent Surface area of the solute Agitation of the solution Color of the solute None 24. ACS: States of matter or solutions Raoult's Law applies to which type of solutions? Non-ideal solutions Ideal solutions Solutions with volatile solutes only Electrolytic solutions None 25. ACS: States of matter or solutions In terms of molecular movement, how do gases differ from liquids? Molecules in gases move slower than in liquids. Molecules in gases are more closely packed than in liquids. Molecules in gases move faster and are further apart than in liquids. There is no significant difference in molecular movement. None 26. ACS: States of matter or solutions What is the effect of adding a non-volatile solute to a solvent on the boiling point of the solvent? It decreases the boiling point. It increases the boiling point. It does not change the boiling point. It decreases then increases the boiling point. None 27. ACS: States of matter or solutions What is true about the vapor pressure of a solution containing a non-volatile solute? It is higher than the vapor pressure of the pure solvent. It is lower than the vapor pressure of the pure solvent. It is equal to the vapor pressure of the pure solvent. Vapor pressure is independent of the presence of a non-volatile solute. None 28. ACS: States of matter or solutions What describes the critical point on a phase diagram? The temperature and pressure above which a liquid can no longer exist. The lowest temperature at which a substance can exist in liquid form. The condition under which all three phases exist in equilibrium. The maximum density point for any substance. None 29. ACS: Energetics (thermochemistry of thermodynamics) For a process that absorbs 40 kJ of heat and does 15 kJ of work on the surroundings, what is the change in internal energy of the system? +25 kJ -25 kJ +55 kJ -55 kJ None 30. ACS: Energetics (thermochemistry of thermodynamics) Which statement about endothermic reactions is correct? They occur spontaneously at all temperatures. They absorb heat, resulting in a positive \(\Delta H\). They decrease the entropy of the surroundings. They always result in a positive \(\Delta G\). None 31. ACS: Energetics (thermochemistry of thermodynamics) If a reaction's entropy change (\(\Delta S\)) is negative and its enthalpy change (\(\Delta H\)) is positive, under what conditions might the reaction be spontaneous? High temperature Low temperature At any temperature Never spontaneous None 32. ACS: Energetics (thermochemistry of thermodynamics) Which condition is not necessary for a reaction to be considered spontaneous under standard conditions? Negative \(\Delta G\) (Gibbs free energy) Positive \(\Delta S\) (Entropy) Temperature independent Negative \(\Delta H\) (Enthalpy) None 33. ACS: Energetics (thermochemistry of thermodynamics) Which statement about endothermic reactions is correct? They occur spontaneously at all temperatures. They absorb heat, resulting in a positive \(\Delta H\). They decrease the entropy of the surroundings. They always result in a positive \(\Delta G\). None 34. ACS: Energetics (thermochemistry of thermodynamics) If a reaction's entropy change (\(\Delta S\)) is negative and its enthalpy change (\(\Delta H\)) is positive, under what conditions might the reaction be spontaneous? High temperature Low temperature At any temperature Never spontaneous None 35. ACS: Energetics (thermochemistry of thermodynamics) What is the sign of \(\Delta G\) for a reaction where \(\Delta H = -150 kJ\) and \(\Delta S = -100 J/K\) at 298 K? Positive Negative Zero Depends on the system size None 36. ACS: Dynamics A reaction mechanism consists of two steps: \( A \rightarrow B \) (slow) and \( B + C \rightarrow D \) (fast). What is the rate-determining ste \( A \rightarrow B \) \( B + C \rightarrow D \) Both steps contribute equally. Cannot be determined without knowing the concentrations. None 37. ACS: Dynamics The activation energy for a reaction is 125 kJ/mol, and the reaction is first order. What would likely happen to the half-life of the reaction if the temperature is increase The half-life decreases. The half-life increases. The half-life remains the same. The half-life initially increases, then decreases. None 38. ACS: Dynamics The rate of disappearance of A in the reaction 2A + B ? C is given by \(-\frac{d[A]}{dt} = k[A]^2[B]\). If the concentration of A is halved, how does the rate of the reaction chang The rate is halved. The rate is quartered. The rate is doubled. The rate remains the same. None 39. ACS: Dynamics What is the effect of doubling the concentration of B in a reaction where the rate law is \( Rate = k[A][B]^2 \ The rate doubles. The rate quadruples. The rate is halved. The rate increases eightfold. None 40. ACS: Dynamics For a reaction with a delta G of +30 kJ/mol at 298 K, what can be said about the spontaneity of the reactio The reaction is spontaneous. The reaction is non-spontaneous. The reaction is at equilibrium. Spontaneity cannot be determined without more information. None 41. ACS: Dynamics The rate of disappearance of A in the reaction 2A + B ? C is given by \(-\frac{d[A]}{dt} = k[A]^2[B]\). If the concentration of A is halved, how does the rate of the reaction chang The rate is halved. The rate is quartered. The rate is doubled. The rate remains the same. None 42. ACS: Dynamics A catalyst increases the rate of a chemical reaction Increasing the equilibrium constant \( K \). Decreasing the equilibrium constant \( K \). Lowering the activation energy. Providing an alternative reaction pathway with a higher activation energy. None 43. ACS: Equilibrium If the equilibrium constant for a reaction at 300 K is 10 and at 350 K is 25, what can be inferred about the reaction? It is exothermic It is endothermic It is neither exothermic nor endothermic It involves no energy changes None 44. ACS: Equilibrium The equilibrium constant for the reaction \( A(g) + B(g) \leftrightarrow C(g) + D(g) \) is 4.0 at a certain temperature. If the initial concentrations of A and B are each 2.0 M, what is the concentration of D at equilibrium? 1.0 M 2.0 M 0.5 M 4.0 M None 45. ACS: Equilibrium In which case will the addition of an inert gas at constant volume to the following reaction \( H_2(g) + I_2(g) \leftrightarrow 2HI(g) \) have no effect on the position of equilibrium? If added at constant pressure If added at constant temperature If added at constant volume If added at varying temperature None 46. ACS: Equilibrium What is the effect on the equilibrium position when the temperature is decreased for the exothermic reaction \( 2SO_2(g) + O_2(g) \leftrightarrow 2SO_3(g) \)? Shifts to the right Shifts to the left No shift Shifts unpredictably None 47. ACS: Equilibrium If the equilibrium constant for a decomposition reaction is less than 1, what can be inferred about the reaction? Products are favored at equilibrium Reactants are favored at equilibrium Neither reactants nor products are favored The reaction does not reach equilibrium None 48. ACS: Equilibrium The reaction \( PC_5(g) \leftrightarrow PCl_3(g) + Cl_2(g) \) has \( K_p = 0.25 \) at 500 K. If the initial pressure of \( PCl_5 \) is 0.4 atm, what is the total pressure at equilibrium? 0.5 atm 0.6 atm 0.7 atm 0.8 atm None 49. ACS: Equilibrium For a reaction where \( \Delta H = -30 \, kJ/mol \) and \( \Delta S = -80 \, J/mol \cdot K \), what is the effect of increasing temperature on the equilibrium constant? Increases Decreases Remains constant First increases, then decreases None 50. ACS: Electrochemistry/redox How many electrons are transferred in the balanced redox reaction involving the conversion of Cu to Cu$^{2+}$ and Ag$^+$ to Ag? 1 2 3 4 None 51. ACS: Electrochemistry/redox Which reaction correctly represents the oxidation that occurs in a standard hydrogen electrode? H$_2$ $\rightarrow$ 2H$^+$ + 2e$^-$ H$^+$ + e$^-$ $\rightarrow$ $\frac{1}{2}$ H$_2$ 2H$^+$ + 2e$^-$ $\rightarrow$ H$_2$ H$_2$ + 2e$^-$ $\rightarrow$ 2H$^-$ None 52. ACS: Electrochemistry/redox What is the oxidation state of chromium in K$_2$Cr$_2$O$_7$? 6 3 12 7 None 53. ACS: Electrochemistry/redox Which species is reduced in the reaction 2 Al(s) + 3 MnO$_2$(s) $\rightarrow$ Al$_2$O$_3$(s) + 3 Mn(s)? Al MnO$_2$ Al$_2$O$_3$ Mn None 54. ACS: Electrochemistry/redox A cell consists of a magnesium electrode in a 1 M Mg$^{2+}$ solution and a copper electrode in a 1 M Cu$^{2+}$ solution. What is the standard cell potential? 2.71 V 3.52 V 1.10 V 2.37 V None 55. ACS: Electrochemistry/redox What is the effect of doubling the surface area of the electrodes in an electrochemical cell? Increases the rate of the redox reaction Decreases the rate of the redox reaction Has no effect on the reaction rate Halves the cell potential None 56. ACS: Electrochemistry/redox The Nernst equation is used to calculate the cell potential under non-standard conditions. What key variable does this equation introduce that is not considered in the standard cell potential? Temperature Pressure Concentration Catalyst presence None 57. ACS: Descriptive chemistry/periodicity Transition metals show variable oxidation states. Which of the following transition metals exhibits the highest oxidation state? Iron Manganese Cobalt Nickel None 58. ACS: Descriptive chemistry/periodicity Which element has the smallest atomic radius in the 3rd period? Sodium Aluminum Silicon Argon None 59. ACS: Descriptive chemistry/periodicity Which group in the periodic table is known for having elements that are all gases at room temperature? Group 1 Group 14 Group 17 Group 18 None 60. ACS: Descriptive chemistry/periodicity Which of the following elements exhibits the highest electronegativity? Fluorine Chlorine Bromine Iodine None 61. ACS: Descriptive chemistry/periodicity What is the typical oxidation state of elements in Group 1 when they form compounds? 1 -1 2 -2 None 62. ACS: Descriptive chemistry/periodicity Which element in the second period forms a diatomic molecule with a triple bond in its most stable form? Carbon Nitrogen Oxygen Fluorine None 63. ACS: Descriptive chemistry/periodicity What is the electron configuration of the outer shell of a typical element in Group 13? s^2 s^2p^1 s^2p^3 s^2p^5 None 64. ACS: Laboratory Chemistry During distillation, a chemist notices that the temperature on the thermometer reads consistently lower than expected. What is the most likely cause of this discrepancy? The distillation path is too long. There is an air leak in the distillation apparatus. The heat source is insufficient. The thermometer is calibrated incorrectly. None 65. ACS: Laboratory Chemistry What is the advantage of using a microwave reactor in organic synthesis over conventional heating methods? It increases the yield of the reaction. It decreases the reaction time. It allows for a higher reaction temperature. It eliminates the need for solvents. None 66. ACS: Laboratory Chemistry What is the primary reason for using an ice bath in an exothermic reaction? To increase the concentration of reactants. To control the rate of reaction. To purify the product. To change the reaction pathway. None 67. ACS: Laboratory Chemistry When calibrating a pH meter, why is it important to use more than one standard buffer solution? To check for the linearity of the pH meter. To extend the life of the pH meter. To increase the accuracy of non-standard solutions. To decrease measurement time. None 68. ACS: Laboratory Chemistry In an analytical chemistry lab, why is it important to perform a blank titration? To determine the end point more accurately. To measure the impurities in the reagents. To establish the titration curve baseline. To consume all of the analyte. None 69. ACS: Laboratory Chemistry Which method is most appropriate for separating non-volatile compounds from a volatile solvent? Filtration. Distillation. Sublimation. Rotavapor (rotary evaporation). None 70. ACS: Laboratory Chemistry In a chemical synthesis involving sensitive reagents, what is the primary reason for using an inert atmosphere? To prevent oxidation of the reagents. To increase the reaction temperature. To purify the reagents. To visualize the reaction. None 1 out of 70 Time is Up! Time's up
