Practice Test 32 - 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 company is choosing piping for a system that transports a warm salt solution (brine) at about 60°C. Requirements: corrosion resistance in salty water (critical), safe for workers to handle (important), and moderate cost (constraint). Which pipe material is the best compromise? Options: - Copper: easy to install; can corrode in chloride-rich solutions over time; moderate cost. - PVC plastic: good corrosion resistance to brine; low cost; softens at higher temperatures but is generally stable at 60°C; cannot be used near open flames. - Plain carbon steel: strong and cheap; rusts quickly in salty water unless heavily coated and maintained.
2. Consider these two reactions (as written): Reaction X: $\Delta H = -15\ \mathrm{kJ}$ Reaction Y: $\Delta H = +15\ \mathrm{kJ}$ Which statement is correct?
3. A teacher says: "Chemical energy comes from breaking and forming bonds (electrons rearrange), while nuclear energy comes from changes in the nucleus." Which choice correctly connects this to the typical energy scale of each type of process?
4. A magnesium atom loses 2 electrons to form $\mathrm{Mg}^{2+}$. If the magnesium isotope is magnesium-24 (Mg-24), how many protons, neutrons, and electrons are in $\mathrm{Mg}^{2+}$?
5. Students are making homemade ice cream using a mixture of ice and salt around a metal canister. The outside of the canister is repeatedly exposed to salty water and then rinsed and dried. The canister must not corrode and must remain safe to touch and use over many cycles. Which chemical property is most important for the canister material?
6. A reaction in solution is slow at room temperature. When the same solution is heated, the reaction becomes fast. Which option correctly links the macroscopic observation to particle motion and collisions?
7. Helium (He) is a noble gas in Group 18 and is used in balloons because it remains a gas even at very low temperatures. Helium has the lowest boiling point of any element. Which justification best explains helium's extremely low boiling point using atomic structure and observable properties?
8. Two curves show product formation: Curve A rises steeply at first and then levels off; Curve B rises more slowly. Which statement is correct?
9. A student lab is choosing a stirring rod for mixing dilute acids and bases (up to 1 M) at room temperature. Requirements: must be chemically resistant (non-negotiable), must be safe to handle (low toxicity), and should be inexpensive because the lab needs many of them. Which material is the best compromise? Options: - Glass: excellent chemical resistance; can break if dropped; low toxicity; moderate cost. - Stainless steel: durable; can slowly corrode in some acids; low toxicity; moderate cost. - Wooden stick: very cheap; absorbs liquids and can react/contaminate solutions over time; can splinter.
10. An oxide ion is written as O²⁻. What is the full electron configuration of O²⁻?
11. Aluminum reacts with chlorine gas: $2\text{Al} + 3\text{Cl}_2 \rightarrow 2\text{AlCl}_3$ If 4.0 mol Al and 3.0 mol $\text{Cl}_2$ are available, what is the limiting reactant?
12. A factory needs piping to carry a dilute sulfuric acid waste stream (about 5% $\text{H}_2\text{SO}_4$) at room temperature. The team selected PVC pipe rather than carbon steel. After 6 months of operation, the PVC showed no visible damage, while a short section of carbon steel used temporarily showed rusting and pitting. Which reasoning best justifies the selection?
13. A science club is building a small hydroponics system. The nutrient solution contains dissolved salts and is kept slightly acidic to help plants absorb nutrients. Tubing and fittings will be in constant contact with this solution for months. The materials must not corrode, must not react with the nutrient solution (changing its chemistry), and must not leach harmful substances that could harm plants. What chemical properties should be required?
14. Chlorine (Cl, Group 17 Period 3), bromine (Br, Group 17 Period 4), and iodine (I, Group 17 Period 5) are halogens. Based on periodic trends, which is the most reactive halogen (best at gaining an electron)?
15. A carbon-14 nucleus changes into nitrogen-14 by emitting a beta particle (an electron). Which type of nuclear process is described?
16. A chloride ion is written as $^{35}\text{Cl}^-$. How many electrons are in this ion?
17. A teacher demonstrates that steel wool left in a damp environment eventually forms rust. A student asks whether salt water makes rusting happen faster, which matters for preventing corrosion near roads treated with salt. Which investigation design best tests the effect of salt on the rate of a chemical change (rusting) with clear variables and evidence?
18. A strip of magnesium is ignited and burns with a bright white light. The air near the flame becomes noticeably warmer, and heat can be felt several centimeters away. What does this indicate about the reaction?
19. Two processes have these enthalpy changes: Process 1: $\Delta H = +25\ \mathrm{kJ/mol}$ Process 2: $\Delta H = +80\ \mathrm{kJ/mol}$ Which process absorbs more heat per mole, and how do you know?
20. Two reactions each involve one "event" per particle: - Reaction X: atoms rearrange electrons to form new chemical bonds. - Reaction Y: an unstable nucleus emits radiation during radioactive decay. Which comparison is most accurate about the energy released per event?

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