ACS General Chemistry practice 147 Questions with Verified Answers,100%CORRECT

ACS General Chemistry practice 147 Questions with Verified Answers Examples of Lewis-Acid based reactions - CORRECT ANSWER H+(aq) + OH-(aq) →← H2O(l), HCl(g) + NH3(g) → NH4Cl(s) H+(aq) + OH-(aq) →← H2O(l) According to the Lewis definition, an acid is a species - CORRECT ANSWER accepting a pair of electrons. All are potential Lewis bases except - CORRECT ANSWER CH4 Which hydrated metal ion is most acidic under conditions of equal molar concentration in water? - CORRECT ANSWER Al3+ Which element in Group 5A forms the most basic oxide? - CORRECT ANSWER Bi 6. In what respect does an atom of magnesium differ from a magnesium ion (Mg2+)? - CORRECT ANSWER The ion has a more stable electronic arrangement than the atom. A certain atom has the symbol 148 73Px. What does this symbol tell about an atom of the element? - CORRECT ANSWER It has 75 neutrons in the nucleus The atomic mass of an element is 32.07 u and its atomic number is 16. The number of protons contained in the nucleus of an atom of this element is - CORRECT ANSWER 16 The atomic mass of an element is 32.07 u and its atomic number is 16. The element forms a simple ion. The ion will most likely have a charge of - CORRECT ANSWER 2- . The nucleus of which atom contains seven neutrons? - CORRECT ANSWER M=17, Z=10 n=1, n=2 In which pair of compounds should the first member be more covalent than the second member? - CORRECT ANSWER SnI4, SnF4 Which is the most complete and best description of a covalent bond? - CORRECT ANSWER a system of two nuclei where each atom donates one electron to the other atom, thus forming a bond Which pair of elements is most likely to react to form a covalently bonded species? - CORRECT ANSWER P and O Which chloride should exhibit the most covalent type of bond? - CORRECT ANSWER BeCl2 The compound of which two elements is most likely to involve covalent bonding? - CORRECT ANSWER 2.8 and 3.0 Chromium metal can be plated from an acidic solution of CrO3. - CORRECT ANSWER 1.73 What time is required to plate 2.08 g of copper at a constant current flow of 1.26 A? Cu 63.5 g•mol-1 Cu2+(aq) + 2e- →← Cu(s) - CORRECT ANSWER 83.6 min Nickel is a transition element and has a variable valence. Using a nickel salt, 2 F (faradays) plate out 39.2 g of nickel. What ions are in the solution of this salt? Ag 107.9 g•mol-1 Cu 63.5 g•mol-1 - CORRECT ANSWER Ni3+ . A given amount of electric charge deposits 2.159 g of silver from an Ag+ solution. What mass of copper from a Cu2+ solution will be deposited by the same quantity of electric charge? Ag 107.9 g•mol-1 Cu 63.5 g•mol-1 - CORRECT ANSWER 0.635 g If each of these ions were reduced to metal with one coulomb, which would yield the greatest mass? - CORRECT ANSWER Ag+(aq) Which is a proper description of chemical equilibrium? - CORRECT ANSWER Reactant molecules are forming products as fast as product molecules are reacting to form reactants. When equilibrium has been reached in the reaction AE + CD →← CE + AD + x kJ in which all substances are in solution, - CORRECT ANSWER escape of some AD by volatilization will increase the concentration of CE Given the reaction 2X(g) + Y(g) →← 2Z(g) ∆H = -335 kJ which combination of pressure and temperature gives the highest yield of Z at equilibrium? - CORRECT ANSWER 1000 atm and 100 °C The reaction for the formation of ammonia by direct combination is - CORRECT ANSWER doubling the concentration of hydrogen Chemical equilibrium is the result of - CORRECT ANSWER opposing reactions attaining equal speeds. Complete and balance the equation for the combustion of ZnS in excess oxygen ? ZnS + ? O2 → ? ZnO + ? - CORRECT ANSWER 2SO2 Balance the equation for the reaction, using no fractional coefficients ? P + ? HNO3 + ? H2O → ? H3PO4 + ? NO - CORRECT ANSWER 5 to 3. Balance the equation for the reaction, using no fractional coefficients ? Cr2O3 + ? KOH +? O2 → ? K2CrO4 + ? H2O - CORRECT ANSWER 8 Why is the equation incorrect? Mg3 + N2 → Mg3N2 - CORRECT ANSWER Some of the subscripts are incorrectly used. A lithium carbide (LixCy) reacts with water as follows: LixCy + H2O → LiOH + C2H2 (unbalanced) What is the simplest formula of the carbide? - CORRECT ANSWER LiC In which gas are the forces between molecules strongest? - CORRECT ANSWER H2O The density of a gas is 1.96 g•L-1 at 1.00 atm and 0 °C. What is the density of this gas at 0.855 atm and 25.0 C? - CORRECT ANSWER 1.54 g•L-1 A 1200 mL sample of helium gas is at a pressure of 350 mmHg and a temperature of 300 K. What volume will this gas sample occupy if the pressure is increased to 700 mmHg and the temperature is increased to 400 K? - CORRECT ANSWER 800 mL . The height of the mercury in the right arm open to atmospheric pressure (760 mmHg) is 100 mm and the height in the left arm is 120 mm. What is the pressure of the gas in the bulb? - CORRECT ANSWER 740 mmHg A sample of nitrogen at pressure P is contained in a sealed syringe with a movable piston. If the volume of the sample were doubled and the absolute temperature tripled, the new pressure of the gas would be - CORRECT ANSWER 1.5 P When equal volumes of 0.1 M solutions of HCl and NaOH are mixed, the total number of ions present will be approximately - CORRECT ANSWER half as great as before mixing. Oxygen and ozone have the formulas O2 and O3 respectively. They are - CORRECT ANSWER allotropes. Which instrument is directly used to determine the relative masses of atoms? - CORRECT ANSWER mass spectrograph An enclosed mixture has a mass of 12.69723±0.00003 g, and after a chemical change occurs the mixture has a mass of 12.69724±0.00003 g. These results show that - CORRECT ANSWER the mass of the enclosed mixture remains constant within the experimental error of the measurement. . The mechanism of electrical conduction in metals is thought to be - CORRECT ANSWER dependent on the movement of valence electrons. Which is not a characteristic of ionic substances? - CORRECT ANSWER Their reactions are generally extremely slow The addition of a catalyst in a chemical reaction - CORRECT ANSWER provides an alternate path with a different activation energy. Which procedure will lower the activation energy for a particular reaction? - CORRECT ANSWER adding a catalyst Which statement most accurately describes the behavior of a catalyst? - CORRECT ANSWER A catalyst reduces the activation energy for a reaction and increases the rate of a reaction. A catalyst will - CORRECT ANSWER alter the pathway (mechanism) of a chemical reaction A student determines the mass of an object using a triple beam balance which is sensitive to 0.01 g. When the beam balances, the rider on one beam is in the notch marked 60 g, the rider on another beam in the notch marked 7 g, and the rider on the third beam, which is graduated by hundredths of a gram, is at zero. Considering significant figures, what mass should be recorded? - CORRECT ANSWER 67.00 g Which instrument is used to measure the gain or loss of heat? - CORRECT ANSWER calorimeter What would be the most rapid method of preparing a saturated aqueous solution of KNO3 if the solubility is known? - CORRECT ANSWER Add an excess over the calculated amount of solute to hot water and cool to 20 °C, with stirring. Incandescent carbon particles cause a gas flame to be yellow. To obtain a hotter blue flame you should - CORRECT ANSWER open the air holes. The electrical conductance of a solution of Ba(OH)2 slowly decreases upon the addition of H2SO4 to a minimum, and then slowly increases. The best experimental evidence for this is - CORRECT ANSWER An electric lamp placed in a circuit in series with the solution becomes dim as the H2SO4 is added and then becomes bright again. . Heating zinc sulfide in air causes the formation of - CORRECT ANSWER ZnO and SO2. The electrical conductance of a solution of Ba(OH)2 slowly decreases upon the addition of H2SO4 to a minimum, and then slowly increases. The best theoretical explanation of this is - CORRECT ANSWER Ions are removed from the solution by the formation of water and insoluble BaSO4 Which group of ions can exist together in water solution in moderate concentration? - CORRECT ANSWER K+, Cl-, Na+, NO3- Which mixture will not yield hydrogen gas? - CORRECT ANSWER zinc and concentrated nitric acid When sodium hydroxide solution is added to magnesium sulfate solution, a white precipitate of magnesium hydroxide is obtained. When sodium hydroxide solution is added to an "unknown" solution, a white precipitate is obtained. To conclude that the unknown solution contains magnesium ion, it must be assumed that - CORRECT ANSWER NaOH forms no white precipitate with any other ion except Mg2+. An sp hybridized central atom can be used to describe the bonding in - CORRECT ANSWER HCN Sulfur dioxide can be described by the structures This implies that - CORRECT ANSWER the two bonds in SO2 are of equal length, and the electronic distribution in the two SO bonds is identical. Which compound would be expected to have the largest dipole moment? - CORRECT ANSWER SO2 (bent) Which is the largest bond angle? - CORRECT ANSWER angle F-Be-F in BeF2 . Which molecule is polar? - CORRECT ANSWER H2S Consider the reaction 2Fe3+(aq) + 2I-(aq) → 2Fe2+(aq) + I2(aq) Which statement is true for the reaction? - CORRECT ANSWER Fe3+ is reduced. In the chemical reaction, Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s), - CORRECT ANSWER metallic zinc is the reducing agent. In this reaction, which substance behaves as the oxidizing agent? Pb + PbO2 + 2H2SO4 → 2PbSO4 + 2H2O - CORRECT ANSWER PbO2 In which group can each substance act as an oxidizing agent? - CORRECT ANSWER Cl2, MnO4-, Cu2+ Which is the strongest oxidizing agent? Na →← Na+ + e- 2.71 V Cd →← Cd2+ + 2e- 0.40 V H2 →← 2H+ + 2e- 0.00 V Ag →← Ag+ + e- -0.80 V - CORRECT ANSWER Ag+ The molecule N2 is isoelectronic with - CORRECT ANSWER cyanide ion, CN- Which isoelectronic ion is the smallest in size? - CORRECT ANSWER Al3+ Which of these isoelectronic ions is the smallest? - CORRECT ANSWER Al3+ In which pair of particles is the first member larger than the second member? - CORRECT ANSWER Li+ ; Be2+ Which ion has the largest radius? - CORRECT ANSWER Cl- 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? O 16.0 g•mol-1 - CORRECT ANSWER XO4 An amino acid has a molar mass of 776.9 g•mol-1 and contains 65.34% iodine by mass. What is the number of iodine atoms per molecule of amino acid? - CORRECT ANSWER four A 6.80 g coin was dissolved in nitric acid and 6.21 g of AgCl was precipitated by the addition of excess sodium chloride, Ag+(aq) + Cl-(aq) → AgCl(s) Calculate the percentage silver in the coin. Atomic Molar Masses Ag 108. g•mol-1 Cl 35.5 g•mol-1 - CORRECT ANSWER 68.7% A and B react exothermically to form a compound. A series of experiments is performed in which varying ratios of A to B are used, with a constant total number of moles, in each case. The observed temperature rise is plotted above. The simplest formula for the compound is probably pic: 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-1 Ni(CO)4171. g•mol-1 - CORRECT ANSWER 96.4% Which molecule has the greatest bond energy? - CORRECT ANSWER H—F For which process is the entropy change per mole the largest at constant temperature? - CORRECT ANSWER H2O(s) → H2O(g) Under which conditions does nitrogen have the largest entropy per mole? - CORRECT ANSWER N2(g) at 80 K and 0.5 atm In which process is entropy decreased? - CORRECT ANSWER freezing water Which reaction has the largest positive entropy change per mole of product formed? - CORRECT ANSWER H2O(l) → H2O(g) A metal forms an oxide salt with the molar mass of 186.94 g/mol. What is the metal in the salt if the metal tends toform a +1 ion? - CORRECT ANSWER Rb How many atoms of oxygen are in 25.0 grams of acetic acid (C2H4O2)? - CORRECT ANSWER 5.02 x 1023 atoms Determine the empirical formula for a compound that is 81.7% carbon and 18.3% hydrogen. - CORRECT ANSWER C3H8 What volume of 0.153 M H2SO4 is needed to neutralize 25.0 mL of 0.106 M NaOH? - CORRECT ANSWER 8.7 mL Calculate the volume of 0.250 M KHCO3 solution needed to make 100.0 mL of 0.0845 M KHCO3 solution? - CORRECT ANSWER 33.8 mL What volume of 0.250 M AgNO3 solution is needed to produce 15.3 grams of solid AgNO3 - CORRECT ANSWER 360 mL Calculate the wavelength of a photon that produces 1.11 x 10-20 J of energy. - CORRECT ANSWER 1.79 x 10-5m Calculate the change in temperature that 25.0 g Al sample will undergo if it absorbs 3.4 kJ of heat? (specific heat of aluminum=0.21cal/goC) - CORRECT ANSWER 154.8 degrees C What will be the final water temperature if 100.0 g Fe at 200oC is dropped into 1000 mL of water at 22.0oC? Specific heat for iron is 0.48 cal/goC and water is 1.00 cal/goC. - CORRECT ANSWER 30.2 degrees C Calculate the volume occupied by 3.6 mole of nitrogen gas at 32oC and 1.14 atm. - CORRECT ANSWER 79.1 L Calculate the density of a gas at 0.948 atm and 84 degrees C that has a molar mass of 39.95 g/mol - CORRECT ANSWER 1.29 g/L What is the percent yield if 175 g of aluminum oxide are produced from 300 g of aluminum and 300 g of oxygen? 4 Al(s) + 3 O2(g) -- > 2 Al2O3(s) - CORRECT ANSWER 30.8% 1. HCl is a strong acid. What is the pH of 200 mL of 0.002 M HCl? - CORRECT ANSWER (B) 2.7 2. The pH of a 0.03 M HCl solution is - CORRECT ANSWER (A) 1.5 3. The pH of a 1.0 * 10-3 M Ba(OH)2 solution at 25 °C is - CORRECT ANSWER (D) 11.3 4. The pH of a solution is 5. If the pH of this solution is decreased to 2, by what factor is the concentration of hydrogen ion increased? - CORRECT ANSWER (E) 1000 5. What is the pH of a 0.01 M NaOH solution? - CORRECT ANSWER (B) 12 6. Which particle has the smallest mass? - CORRECT ANSWER (C)beta particle 7. A sodium ion differs from a sodium atom in that the sodium ion - CORRECT ANSWER (B) has fewer electrons. 8. What is the number of unpaired electrons in an isolated free iron atom (atomic number 26) in the ground state? - CORRECT ANSWER (D) four 9. Which ion has twenty-six electrons? - CORRECT ANSWER (C) Ni2+ 10. The element in Period 5, Group 3A, has the outer electron configuration - CORRECT ANSWER (A) 5s25p1 11. Use the section of a periodic table to determine the type of bond that will form between W and E. - CORRECT ANSWER (A) covalent 12. Which characteristic is generally true of nonmetallic oxides? - CORRECT ANSWER (B)They are in general covalent compounds. 13. Which atom description represents an element that could form a covalent compound with an atom of a nonmetal? - CORRECT ANSWER D) Nucleus 8p, 10n n=1 2e; n=2 6e 14. Hydrogen bonding is shown by molecules containing hydrogen attached to - CORRECT ANSWER (A) highly electronegative atoms. 15. Which best represents hydrogen bonding in liquid methanol (CH3OH)? - CORRECT ANSWER ( C) O---H 26. The ions present in solid silver chromate Ag2CrO4 are - CORRECT ANSWER (A) Ag+ and CrO42- 27. Substances that contain water incorporated in the crystal in definite proportions by weight are - CORRECT ANSWER (C)hydrates. 28. Three compounds having the formulas NaCl, CaCl2, and AlCl3 exist. Comparison of these formulas indicates that - CORRECT ANSWER (D) the combining capacities of the metals are different. 29. The chemical equation 2CO2 --> 2CO + O2 informs us that - CORRECT ANSWER (D)regardless of conditions, the decomposition of l mol of CO2 will yield l mol of CO and 1/2 mole of O2. 30. At constant volume, the pressure of gas Y increases with increasing temperature because as the temperature increases, - CORRECT ANSWER (A) molecules of Y move faster 31. A student collected 40 mL of H2 gas when the temperature was 20 °C and the pressure was 720 mmHg. The next day the temperature was 20 °C, but he had only 38.4 mL of gas. The new pressure is - CORRECT ANSWER (E)760 mmHg 32. A container holds 3.0 g of hydrogen. If it is evacuated and filled with methane, CH4, at the same temperature and pressure, what mass of methane does it now hold? - CORRECT ANSWER (E) 48 g 33. If the temperature of 10.0 L of a gas is decreased from 0.00 °C to 27.3 K and the pressure is increased from 10.0 atm to 100.0 atm, the new volume will have a value nearest to - CORRECT ANSWER (D) 0. 100 L. 34. Both the pressure and the absolute temperature of a certain gas sample are doubled. In the absence of dissociation, the density of the gas is - CORRECT ANSWER (D)decreased by one-fourth 35. Most nonmetals - CORRECT ANSWER (D) form anions more readily than cations. 36. Scientists have not been able to attain a temperature lower than about - 273 °C. Theory predicts that we shall never reach a temperature much lower than this because - CORRECT ANSWER (D)molecules cannot have kinetic energy less than zero. 37. Which is most likely to be characteristic of a atom showing metallic properties? - CORRECT ANSWER (D)fewer than three valence electrons 38. Which is correct for most metals? - CORRECT ANSWER (E)give up electrons to chlorine 39. Antimony reacts spontaneously with chlorine to form antimony chloride. The reaction would proceed with reduced velocity if one were to - CORRECT ANSWER (B) use larger particles of antimony. 55. The molecule O=C=N-H has been detected in gas clouds between stars. The predicted C—N—H bond angle is about - CORRECT ANSWER (D) 120° 56. The bond type and molecular polarity of SiCl4 are - CORRECT ANSWER (A) BOND TYPE: polar/ POLARITY OF MOLECULE: nonpolar 57. Which of these is a nonpolar molecule? - CORRECT ANSWER C) C2F4 58. Which molecule is nonpolar? - CORRECT ANSWER (A) CCl4 59. Which molecule has the largest dipole moment? - CORRECT ANSWER (D) H2O 60. Which process represents a general method for the preparation of a metal from its compounds? - CORRECT ANSWER (B)reduction 61. Which reaction involves neither oxidation nor reduction? - CORRECT ANSWER (B) Formation of water by action of sodium hydroxide and nitric acid 62. The fact that Na3AsS3 can be converted into Na3AsS4 in an aqueous suspension of sulfur indicates that sulfur - CORRECT ANSWER (C) can be an oxidizing agent. 63. The action of hot, concentrated sulfuric acid on copper is best explained by the - CORRECT ANSWER (B) oxidizing property of concentrated sulfuric acid 64. Under certain conditions H2O2 can act as an oxidizing agent; under other conditions, as a reducing agent. What is the best experimental evidence for this? - CORRECT ANSWER (C ) H2O2 will decolorize KMnO4 solutions in the presence of an acid and will turn black lead sulfide to a white compound. 65. Which ion has the largest radius? - CORRECT ANSWER (A) Te2- 66. Which ion is the largest? - CORRECT ANSWER (D) S2- 67. Which pair is given in the order of increasing size? - CORRECT ANSWER (C) Fe3+, Fe2+ 68. What happens when a bromine atom becomes a bromide ion? - CORRECT ANSWER (D) It becomes a particle with a larger diameter. 69. The sizes of metal atoms - CORRECT ANSWER (B) generally increase progressively from top to bottom in a group in the periodic table. 70. 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) - CORRECT ANSWER (C) 96.3% 71. A 2.000 g sample of a Ni-Tl-Zn alloy is dissolved in nitric acid and 1.750 g of thallium(I) iodide, TlI, is precipitated by the addition of hydriodic acid. Calculate the percentage of thallium in the alloy. - CORRECT ANSWER (B) 53.98% 72. A piece of silver foil having a mass of 0.5840 g had become tarnished because of formation of Ag2S, with a mass increase of 0.0010 g. What percentage of the original silver has been converted to Ag2S? - CORRECT ANSWER (B) 1.2% 73. What is the percentage of nitrogen by mass in (NH4)3PO4? - CORRECT ANSWER (D) 42/149 * 100% 74. A 2.00 g mixture of NaCl and NaNO3 dissolved in water required 90 mL of 0.10 M AgNO3 to precipitate all the chloride. What is the mass percentage of NaCl in the original sample? - CORRECT ANSWER (B) 26 75. Which reaction has the largest positive entropy change per mole of CO formed? - CORRECT ANSWER (B) CH3OH(g) CO(g) + 2H2(g) 76. At any given temperature the entropy of a mole of liquid, compared to the entropy of a mole of its vapor, is always - CORRECT ANSWER (A) smaller. 77. When Al2O3(s) is formed from the elements at standard conditions, the values of ΔH0 and ΔG0 at 298 K are -1617 kJ•mol-1 and -1577 kJ•mol-1, respectively. The standard entropy of formation per mole, in joules per degree, will be - CORRECT ANSWER (A) -315 What is ΔG0 for this reaction at 298 K? 2SO2(g) + O2(g) * 2SO3(g) - CORRECT ANSWER (A) -142 kJ 79. Consider ice in equilibrium with liquid water at 273 K. Which of the following relationships is correct for G(s), the free energy per mole of ice and G(l), the free energy per mole of the liquid? - CORRECT ANSWER (D) G(s) equals G(l); neither equals 0 80. Which reaction is spontaneous in the direction written? - CORRECT ANSWER (D) 2Al + 3Zn2+ * 2Al3+ + 3Zn