Practice Test 28 - High School Chemistry

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

Start practice test

1. A student argues: "A campfire can release a lot of heat, so chemical reactions must release more energy per atom than nuclear reactions." Which response best corrects the student's misunderstanding?​
2. A student mixes two clear solutions in a cup. After stirring, the mixture remains clear, but the temperature drops noticeably and a new smell appears that was not present in either solution before mixing. Which combination of observations suggests a chemical change?
3. In a lab, 50 mL of hydrochloric acid and 50 mL of sodium hydroxide (both initially at 22°C) are mixed in a foam cup. After stirring, the thermometer reads 30°C. Which conclusion is supported by these observations?
4. A lab group claims: "The reaction between aqueous barium chloride and aqueous sodium sulfate forms an insoluble product." They mix the two clear solutions at room temperature and record the following observations: 1) A white solid appears immediately. 2) The mixture becomes cloudy and then settles into a solid layer and a clear liquid. 3) The temperature changes from $22.0^\circ\text{C}$ to $22.5^\circ\text{C}$. 4) Both starting solutions were colorless. Which piece of evidence best supports the claim?
5. A community near a proposed nuclear waste storage facility is debating whether to accept it. The facility could centralize and monitor radioactive waste more securely than scattered temporary sites, but residents worry about long-term containment, potential leaks into groundwater, and the fairness of hosting a hazard that benefits electricity users elsewhere. Which option best evaluates the trade-offs?
6. A strip of shiny gray metal is placed into a blue solution. After a few minutes, the blue color fades, and a reddish-brown coating appears on the metal's surface. Which combination of observations supports the claim that a chemical reaction occurred?
7. A school's maintenance team needs a protective coating for outdoor metal railings. The railings are exposed to rain, sunlight, and occasional splashes from pool water that contains chlorine-based chemicals. Which chemical properties are most important for the coating to last?
8. Radium-226 undergoes radioactive decay: $^{226}_{88}\mathrm{Ra} \rightarrow {}^{222}_{86}\mathrm{Rn} + {}^{4}_{2}\mathrm{He}.$ What type of decay is this?
9. A student repeated the same neutralization test three times to check reliability. Each trial mixed 25.0 mL of 0.50 M HCl with 25.0 mL of 0.50 M NaOH in a foam cup. The initial temperatures of both solutions were 22.0°C. The final temperature was recorded after stirring for 30 s. Which statement best describes the data quality and pattern?​
10. A student says: "Chemical reactions break bonds, so they must always absorb energy; nuclear reactions are the ones that release energy." Which correction best reflects the real comparison of chemical vs nuclear energy scales?
11. Magnesium (Mg) has electron configuration [Ne]3s2 and chlorine (Cl) has electron configuration [Ne]3s2 3p5. Both are in period 3. Chlorine has a smaller atomic radius than magnesium. Which explanation best connects electron configuration to this trend?
12. A team built a simple solar oven and covered the inner walls with aluminum foil tape to reflect heat. They used a common adhesive-backed foil tape. Testing: - At $90\,^{\circ}\mathrm{C}$, the tape stayed attached. - At $120\,^{\circ}\mathrm{C}$, the adhesive softened and the foil began to peel off. - The oven needs to reach $130\,^{\circ}\mathrm{C}$ for cooking. Which refinement best addresses the failure shown by the test data?
13. A concentration-versus-time graph shows a reactant $[A]$ decreasing. Four points are marked on the curve: W (very early, steep part), X (early-middle, still fairly steep), Y (late, gentle slope), and Z (very late, almost horizontal). At which point is the reaction rate the fastest?
14. A single-step energy diagram shows reactants at 75 kJ, a peak at 140 kJ, and products at 70 kJ. Which statement best describes the reaction based on the diagram?
15. A student says, "Breaking bonds releases energy, which is why reactions can give off heat." Which correction is scientifically accurate?
16. A student compares two different mixings at the same initial temperature (21.0°C) in sealed containers. Mixing 1: - 20.0 mL solution X + 20.0 mL solution Y - After mixing: temperature = 29.0°C; mixture turns cloudy; a solid forms Mixing 2: - 20.0 mL solution M + 20.0 mL solution N - After mixing: temperature = 21.0°C; mixture stays clear; no solid forms Which conclusion is best supported by the data?
17. The synthesis of ammonia is represented by the balanced equation $\text{N}_2 + 3\text{H}_2 \rightarrow 2\text{NH}_3.$ According to the coefficients, how many moles of $\text{H}_2$ react per 1 mole of $\text{N}_2$?
18. In the nuclear equation $^{238}_{92}\text{U} \rightarrow ^{234}_{90}\text{Th} + X$, what particle is represented by $X$?
19. Students investigate: How does temperature affect the volume of gas produced in a reaction? They place 0.50 g of baking soda (NaHCO$_3$) into each of three flasks. Each flask receives 25.0 mL of vinegar (5% acetic acid) that has been pre-warmed or pre-cooled to 10C, 25C, or 40C. Immediately after mixing, they attach a balloon to each flask and record the balloon circumference after 2 minutes. Which variable is being deliberately changed between trials (independent variable)?
20. Consider the transformation: potassium atom (K, atomic number 19) potassium ion (K). Which statement correctly describes what changed and why K forms?

Practice tests