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Practice Test 37 - High School Chemistry

20 questions. Answer them in any order, then submit to see your score and every explanation.

  1. Which electron configuration correctly represents oxygen (O), atomic number 8?​
  2. A student adds 2.00 g of magnesium metal, Mg(s), to 25.0 mL of hydrochloric acid, HCl(aq), in an open beaker. The beaker is placed on a balance. Mass measurements: - Beaker + HCl(aq) before adding Mg: 78.50 g - Mg added: 2.00 g - Beaker + contents after reaction stops (bubbling stops): 79.60 g Other observations: vigorous bubbling occurred; the solution warmed from 21.0°C to 28.0°C. Which interpretation best matches the data?
  3. Inside the Sun, two small hydrogen nuclei combine at extremely high temperature and pressure to form a larger helium nucleus, releasing energy. What type of nuclear process is this?
  4. Fluorine (F) and chlorine (Cl) are both in group 17. Fluorine and chlorine both commonly form −1-1 ions in ionic compounds. Why do these two elements show similar chemical behavior?
  5. Zinc chips (same mass and similar size) are added to 25 mL of HCl at the same temperature. Only the acid concentration changes.
    Trial[HCl] (M)ObservationTime for bubbling to largely stop
    10.5slow bubbling80 s
    21.0moderate bubbling40 s
    32.0rapid bubbling20 s
    Which best explains the trend in reaction time?
  6. Two beakers each contain 50 mL of 1.0 M HCl at 25°C. In Beaker A, a single large piece of zinc is added. In Beaker B, the same mass of zinc is added as many small pieces. Beaker B produces hydrogen bubbles much more vigorously and finishes sooner. What is the best reason?
  7. A piece of dry ice (solid carbon dioxide) is left on a lab bench at room temperature. Over time, the solid shrinks and a fog-like gas appears around it until the solid is gone. What kind of change is this?
  8. A coastal community is deciding whether to build a new nuclear power plant. Supporters note that nuclear fission can generate large amounts of reliable electricity with very low greenhouse gas emissions during operation and uses a small volume of fuel compared with coal. Opponents point out that the plant would produce long-lived radioactive waste that must be securely stored for thousands of years, and that rare accidents (such as Fukushima) can release radiation into the environment. Which statement best balances the benefits and risks for an informed decision?
  9. A reaction is observed to be endothermic overall (it absorbs heat from the surroundings). Which statement best describes the bond-energy balance for an endothermic reaction?
  10. A lab group built a small device to store and dispense 70% isopropyl alcohol for cleaning electronics. They chose a high-density polyethylene (HDPE) squeeze bottle instead of a polystyrene cup or an unlined metal container. After repeated refills for 3 months, the HDPE bottle stayed flexible and did not crack or become cloudy; the polystyrene cup became brittle and developed crazing. Which reasoning best justifies the HDPE choice?
  11. A piece of paper is torn into smaller pieces. Before, it is one sheet; after, it is several smaller pieces of the same paper. Which best describes the change?
  12. A student compares two beakers containing the same reactants in solution. Beaker 1 is concentrated (many reactant particles in the same volume). Beaker 2 is diluted (fewer reactant particles in the same volume). The concentrated beaker shows product formation sooner. Which collision-theory statement best explains this observation?
  13. A neutral atom has 2 electrons in the first shell, 8 in the second shell, and 5 in the third shell (total 15 electrons). Which electron configuration matches this shell distribution?​
  14. Arrange these alkali metals in order of increasing reactivity with water, using their periodic positions: Li (Group 1 Period 2), Na (Group 1 Period 3), K (Group 1 Period 4).
  15. Two reactions have the following enthalpy changes: Reaction 1: ΔH=−50 kJ\Delta H = -50\ \mathrm{kJ} Reaction 2: ΔH=−200 kJ\Delta H = -200\ \mathrm{kJ} Which reaction releases more heat to the surroundings (per reaction as written)?
  16. A student heats ice in a closed container and records observations. Before heating: - Ice (H2O(s)): mass = 20.0 g, temperature = 0.0°C, state = solid After heating: - Water (H2O(l)): mass = 20.0 g, temperature = 0.0°C, state = liquid - No bubbles, no color change, no new substances observed What does the data indicate?
  17. A city wants to replace underground water service lines. Requirements: (1) must not leach toxic substances into drinking water, (2) must resist corrosion in moist soil, (3) should last decades, and (4) cost matters because many miles will be installed. Which material is the best trade-off? Materials: - Lead: easy to shape and long-lasting; but toxic (non-negotiable safety issue). - Copper: good durability and acceptable for drinking water; but expensive and can corrode in some soils. - PEX plastic: inexpensive; corrosion-resistant; flexible; but can be damaged by UV light during storage/installation and has temperature limits.
  18. In a lab, 5 g of ammonium chloride is dissolved in 50 mL of water. The thermometer reading drops from 23°C to 17°C after stirring, and the beaker feels noticeably cooler. What best describes the energy transfer?
  19. Consider the reaction pathway idea: (1) reactant bonds break, (2) atoms rearrange, (3) product bonds form. Which statement best describes the energy changes during steps (1) and (3)?
  20. For the combustion reaction CH4+2O2→CO2+2H2O\mathrm{CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O} if 3.0 mol3.0\ \text{mol} of CH4\mathrm{CH_4} burn completely, how many moles of O2\mathrm{O_2} are required?

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