Practice Test 46 - High School Chemistry

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

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1. The nuclear equation $^{226}_{88}\text{Ra} \rightarrow ^{222}_{86}\text{Rn} + ^{4}_{2}\text{He}$ is an example of which process?
2. The following elements are all in period 3: sodium (Na) is in group 1, aluminum (Al) is in group 13, and chlorine (Cl) is in group 17. Which element has the smallest atomic radius?
3. A neutral atom has 9 protons and a mass number of 19. What element is it, and how many neutrons does it have?
4. A community pool needs a pipe section to carry chlorinated water (contains low levels of chlorine compounds) outdoors in sunlight. Requirements: (1) resist corrosion/chemical attack from chlorinated water, (2) tolerate sun/UV exposure, and (3) keep costs low. Options: - PVC pipe: good chemical resistance; low cost; can degrade/brittle under long-term UV unless protected. - Copper pipe: more expensive; can corrode in some chlorinated water conditions. - Stainless steel pipe: excellent corrosion resistance; very expensive. Which is the best trade-off given that cost is important but the pipe will be outdoors for years?
5. 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?
6. A single-step reaction energy diagram has reactants at 40 kJ, a peak at 100 kJ, and products at 40 kJ. Which statement best describes the overall energy change $\Delta H$?
7. A student argues: "If you burn enough wood, you can match the energy of a nuclear reactor, so chemical reactions can release as much energy per atom as nuclear reactions." Which response best addresses the mistake in the student's reasoning?
8. Calcium (Ca) is a Group 2 element with atomic number 20. When it forms an ion, it becomes Ca²⁺. How many electrons are transferred, and what is the main reason Ca forms a 2+ ion?
9. A student mixes baking soda and vinegar in an open beaker. Reaction: $\mathrm{NaHCO_3(s) + HC_2H_3O_2(aq) \rightarrow CO_2(g) + H_2O(l) + NaC_2H_3O_2(aq)}$. Masses measured: - Before: beaker + contents = 120 g - After bubbling stops: beaker + contents = 116 g Which statement best explains the 4 g decrease?
10. Calcium carbonate decomposes as shown: $\mathrm{CaCO_3 \rightarrow CaO + CO_2}$ If $0.75 \text{ mol}$ of $\mathrm{CaCO_3}$ decompose completely, how many moles of $\mathrm{CO_2}$ are produced?
11. A patient with thyroid cancer is offered treatment with radioactive iodine, which can target thyroid tissue and destroy cancer cells. The hospital explains that the treatment can be life-saving but also involves exposure to ionizing radiation and may cause side effects, requiring careful dosing and safety instructions to limit exposure to others. Which option best balances the benefits and risks of this medical use of nuclear technology?
12. Three descriptions are given: 1) A heavy nucleus breaks into two smaller nuclei and releases neutrons. 2) Two small nuclei combine to form a larger nucleus. 3) One unstable nucleus emits a particle and becomes more stable. Which list correctly matches (1), (2), and (3) to fission, fusion, and radioactive decay?
13. For a reaction at constant pressure, $\Delta H = H(\text{products}) - H(\text{reactants})$. If a reaction has $\Delta H = -120\ \mathrm{kJ}$, which statement must be true?
14. Magnesium (Mg) is in Group 2 with 2 valence electrons (ends in 3s²). Chlorine (Cl) is in Group 17 with 7 valence electrons (ends in 3s² 3p⁵). When magnesium reacts with chlorine, MgCl₂ forms. Which explanation best connects valence electrons to the ions formed?
15. Chlorine (Cl) has atomic number 17. How many valence electrons does a neutral chlorine atom have?​
16. A decay is shown: $^{40}_{19}\text{K} \rightarrow ^{40}_{20}\text{Ca} + X.$ Which particle is $X$?
17. Potassium (group 1, period 4) has electron configuration [Ar]4s1 and sodium (group 1, period 3) has electron configuration [Ne]3s1. Potassium has a lower first ionization energy than sodium. Which explanation best connects this to electron configuration?
18. Methane combustion can be written as $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$. Conceptually, the reaction breaks C–H and O=O bonds and forms C=O and O–H bonds. Why is combustion typically exothermic (releases heat) in terms of bonds?
19. A nucleus undergoes alpha decay: $X \rightarrow ^{210}_{82}\text{Pb} + ^{4}_{2}\text{He}.$ What is the original nucleus $X$?
20. A class builds a cold-pack pouch that holds an ammonium nitrate solution. Initial design: a thin nylon film pouch was chosen because it is flexible and strong. Test evidence: After 20 freeze–thaw cycles (from $-10^\circ\text{C}$ to $20^\circ\text{C}$), several pouches develop slow leaks along the heat-sealed seam, but the film away from the seam remains intact. Dye testing shows leaks start at tiny gaps in the seal line. Which refinement best uses the evidence to improve the design without changing the pouch's basic shape?

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