Practice Test 29 - 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 tested how hydrochloric acid concentration affects the reaction time for a fixed mass of calcium carbonate chips. Each trial used $2.00\,\text{g}$ of CaCO$_3$ and $25.0\,\text{mL}$ of HCl at $22.0\,^{\circ}\text{C}$. The student measured the time until bubbling stopped. What trend is visible in the data?
2. Rust formation (simplified) can be represented by the balanced equation $\mathrm{4Fe + 3O_2 \rightarrow 2Fe_2O_3}$. What is the mole ratio of $\mathrm{Fe}$ to $\mathrm{Fe_2O_3}$?
3. Melting ice at $0^\circ\mathrm{C}$ is $\mathrm{H_2O(s) \rightarrow H_2O(l)}$ with $\Delta H = +6.0\ \mathrm{kJ/mol}$. Which statement is correct?
4. A student conducts two trials. Trial 1: 3.0 g of sugar is stirred into 50 mL of water. The sugar disappears, the solution stays clear, and the temperature changes from 21.0°C to 20.2°C. Trial 2: 3.0 g of sugar is heated strongly in a dry test tube. The sugar turns brown, then black, and a noticeable burnt smell appears. A dark solid remains stuck to the tube. For Trial 2, did a chemical reaction occur? Choose the best CER justification.
5. A student reacts calcium carbonate with the same volume and concentration of hydrochloric acid at the same temperature. Each trial uses the same mass of calcium carbonate, but in different forms. Results: - Large chips: gentle fizzing; finishes in ~150 s - Small chips: steady fizzing; finishes in ~60 s - Powder: vigorous fizzing; finishes in ~15 s Which statement best explains why the powdered calcium carbonate reacts fastest?
6. A student opens a bottle of carbonated water. As soon as the cap is removed, bubbles rise to the top and a fizzing sound is heard, but nothing else changes. Which statement best describes the bubbling in this situation?
7. Iron reacts with oxygen to form iron(III) oxide: $4\text{Fe} + 3\text{O}_2 \rightarrow 2\text{Fe}_2\text{O}_3.$ If $8.0\ \text{mol}$ of $\text{Fe}$ react completely, how many moles of $\text{Fe}_2\text{O}_3$ are produced?
8. Helium (He) has the lowest boiling point of any element and is used in balloons because it stays a gas even at very low temperatures. Which justification best explains helium's extremely low boiling point using atomic structure and periodic trends?
9. Fluorine (F) has electron configuration [He]2s2 2p5 and chlorine (Cl) has electron configuration [Ne]3s2 3p5. Chlorine has a larger atomic radius than fluorine. What about their electron configurations best explains why?
10. A coastal bridge design team chose 316 stainless steel fasteners instead of carbon steel fasteners. The bridge is exposed to sea spray (saltwater). In a 12-month outdoor test near the shore, carbon steel fasteners developed heavy rust, while 316 stainless steel fasteners showed only minor surface discoloration. Which reasoning best justifies the design decision?
11. A student compares oxygen (O) and sulfur (S), which are both in Group 16. Oxygen is a gas at room temperature, while sulfur is a solid. Which justification best explains this difference using periodic position and particle-level attractions (no advanced bonding details needed)?
12. Carbon-14 and carbon-12 are isotopes of carbon. Which statement correctly compares them?
13. The following elements are all in period 4: potassium (K) is in group 1, gallium (Ga) is in group 13, and bromine (Br) is in group 17. Which element has the highest first ionization energy?
14. A food company is selecting a packaging film for sliced apples. Two options were tested: (1) a conventional polyethylene (PE) film and (2) a compostable polylactic acid (PLA) film. In a shelf-life trial, apples in PLA film browned faster because the film allowed more oxygen to pass through, but the PLA film fully disintegrated in an industrial composting test within 12 weeks, while PE did not change. The company chose PLA for a product line marketed as compostable, accepting the shorter shelf life. Which justification best supports this decision using chemical properties and trade-offs?
15. In the nuclear equation $^{238}_{94}\mathrm{Pu} \rightarrow \,^{234}_{92}\mathrm{U} + \,^{4}_{2}\mathrm{He},$ what is the product nucleus formed (the element and mass number)?
16. A sports team wants a reusable water bottle that can be cleaned in a dishwasher using hot water and detergent. The bottle will be exposed to repeated heating and cooling cycles and must not release chemicals into the water or develop strong odors from chemical breakdown. Which set of chemical properties best matches this need?
17. A single-step reaction energy diagram shows reactants at 90 kJ, a peak at 140 kJ, and products at 60 kJ. Which statement correctly interprets both $E_a$ and $\Delta H$ from the diagram?
18. Select the balanced form of the reaction (smallest whole-number coefficients): Ca(OH)2 + HCl → CaCl2 + H2O
19. Two molecules must collide in a particular way for a reaction to occur (for example, a reactive end of one must meet a reactive region of the other). At room temperature, many collisions occur but only a small amount of product forms. Which option best explains this using collision theory?
20. An electronics maker needs a transparent cover for outdoor sensors exposed to sunlight and oxygen. Two plastics were considered: acrylic (PMMA) and polycarbonate (PC). After 6 months of accelerated UV exposure, the polycarbonate covers yellowed noticeably, while acrylic stayed clear. The team chose acrylic despite acrylic being more brittle. Which option best justifies this decision using chemical reasoning and trade-offs?

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