Practice Test 10 - High School Chemistry

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

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1. A student investigated how the amount of reactant affects the amount of gas produced. Different masses of sodium bicarbonate (NaHCO$_3$) were added to excess vinegar in identical flasks. The total CO$_2$ collected after 60 s was measured.

   Mass of NaHCO$_3$ (g)	CO$_2$ collected in 60 s (mL)
   0.50	115
   1.00	230
   1.50	345
   2.00	460

   Which statement best describes the relationship between mass of NaHCO$_3$ and CO$_2$ volume collected (within this tested range)?
2. An instant cold pack is activated by breaking an inner water pouch so the water mixes with a salt inside. The pack temperature drops from 24°C to 9°C and feels cold in your hand. What does this indicate about the process?
3. A student heats a beaker of water on a hot plate. After several minutes, bubbles form at the bottom and rise to the surface; the water temperature increases steadily. Which observation is NOT evidence of a chemical reaction?
4. Using the balanced equation $\mathrm{N_2 + 3H_2 \rightarrow 2NH_3}$ how many moles of $\mathrm{NH_3}$ can be produced from $6.0\ \text{mol}$ of $\mathrm{H_2}$ (assume $\mathrm{N_2}$ is in excess)?
5. A reaction energy diagram for a single-step reaction shows a curve that rises from the reactants to a highest point, then falls to the products. What does the highest point (the peak) represent?
6. Which statement correctly describes the trend in first ionization energy for main-group elements?
7. A student team designs a reusable spray bottle to hold a household bleach cleaner (about 5% sodium hypochlorite). They choose a clear polycarbonate (PC) bottle because it is rigid and transparent. After 3 weeks of daily use, the bottle shows fine cracks near the neck and becomes cloudy. A simple comparison test finds that PC coupons soaked in bleach lose mass and develop surface cracks, while high-density polyethylene (HDPE) coupons show no visible change. Based on this evidence, what refinement would best improve the design while keeping the bottle reusable?
8. A food company wants to use food irradiation to reduce bacteria in packaged spices and extend shelf life without adding chemical preservatives. Regulators note that irradiation does not make the food itself radioactive, but it requires strict controls for the radiation source and worker safety, and some consumers worry about the technology. Which statement best evaluates the trade-offs?
9. To test how surface area affects reaction rate, a student reacted calcium carbonate with acid. Each trial used 1.00 g CaCO$_3$ and 50.0 mL of 1.0 M HCl at 22.0°C. The only change was the form of CaCO$_3$. Data table: - CaCO$_3$ form: large chips, small chips, powder - Time until fizzing stopped (s): 210, 125, 55 What pattern does the data show?
10. Two clear, colorless liquids are mixed in a sealed plastic bag: 50 mL of water and 50 mL of rubbing alcohol (isopropyl alcohol). The bag is gently shaken. Observations and data: - The mixture remains clear and colorless - Temperature: $22.0^\circ\text{C}$ before, $23.0^\circ\text{C}$ after 2 minutes - No bubbles, odor change, or solid formation observed - The mixture can be separated later by simple distillation (two liquids collected at different temperatures) Based on the evidence, which CER justification is best?
11. A cafeteria manager notices that sliced apples sometimes turn brown faster when stored in certain plastic containers. The manager needs to know whether the browning is a chemical change (oxidation) so they can choose better storage methods to reduce food waste. Which experiment design best answers the testable question: "Does container type affect the rate of chemical change (browning) in apple slices?"
12. Carbon dioxide is produced by $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}.$ If you have 4.0 mol $\text{CH}_4$ and 6.0 mol $\text{O}_2$, what is the maximum amount of $\text{CO}_2$ that can form?
13. A student drops a piece of magnesium ribbon into a test tube containing hydrochloric acid. Immediately, many bubbles form on the metal, the test tube becomes warm, and the magnesium ribbon gets smaller until it is gone. After the reaction, the solution is clear. Data: - Temperature before: 20.5°C - Temperature after 1 minute: 32.0°C Did a chemical reaction occur? Choose the best CER justification.
14. A nucleus releases a gamma ray (high-energy electromagnetic radiation) but does not split into two large fragments and does not combine with another nucleus. What type of nuclear process is this?
15. A student reacts identical 2 cm strips of magnesium ribbon with 50 mL of 1.0 M HCl in two beakers. All conditions are the same except temperature. In Trial 1 at 20°C, bubbling lasts about 60 s. In Trial 2 at 40°C, bubbling lasts about 15 s. Which statement best explains why Trial 2 is faster?
16. A neutral atom has 9 protons and mass number 19. How many electrons does it have?
17. A wooden match is struck and begins to burn. The flame gives off heat and light, smoke rises, and ash remains after the match stops burning. Classify the change based on the observations.
18. A student places a small piece of magnesium ribbon into 50 mL of vinegar in a cup. Observations/data: - Immediate bubbling begins on the metal surface - The magnesium ribbon gets smaller over 5 minutes - Temperature increases from $23^\circ\text{C}$ to $30^\circ\text{C}$ - After bubbling stops, the liquid remains clear Did a chemical reaction occur? Choose the best CER-style justification.
19. A student combines 20 mL of hydrogen peroxide solution with a small amount of yeast in a flask. Observations/data: - Foam rapidly rises in the flask and overflows - The flask feels warm to the touch - A glowing splint held near the mouth of the flask relights (after foam is moved aside) - No solid precipitate is observed in the liquid Did a chemical reaction occur? Choose the best CER justification.
20. A plant is placed under a bright grow light. Over time, it uses carbon dioxide and water to produce glucose and oxygen. The process only continues while light energy is provided. Which statement best classifies this process in terms of energy transfer?

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