Practice Test 31 - High School Chemistry

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

A student wants to test how concentration affects reaction rate using magnesium ribbon and hydrochloric acid. The student uses the same length of Mg ribbon and keeps the temperature constant. Which change would best isolate the effect of concentration on the reaction rate?
A word equation is shown: large nucleus $\rightarrow$ two smaller nuclei + neutrons + energy. Which type of nuclear process does this represent?
Two identical beakers each contain 100 mL of 0.50 M sodium thiosulfate solution at 23°C. A fixed amount of dilute hydrochloric acid is added to each beaker to start a reaction that forms a cloudy sulfur precipitate. In Beaker 2, the thiosulfate solution is first diluted with water to 0.25 M (same final volume of liquid as Beaker 1). All other conditions are kept constant. How does the rate of cloudiness formation in Beaker 2 compare with Beaker 1?
Fluorine (F) and iodine (I) are both halogens in Group 17. In a lab, fluorine reacts much more vigorously than iodine with many metals. Which reasoning best justifies this difference using periodic trends and atomic structure?
A student tested how surface area affects reaction rate by reacting calcium carbonate (CaCO $_3$ ) with $1.0\,\text{M}$ HCl at $22.0\,^{\circ}\text{C}$ . Each trial used $2.00\,\text{g}$ of CaCO $_3$ and $25.0\,\text{mL}$ of acid. The student measured the time until bubbling stopped. Which statement best describes the relationship between surface area and reaction time?
Given the balanced equation: $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$ If $3.0$ mol of $\text{CH}_4$ burn completely, how many moles of $\text{O}_2$ are required?
To explore "How does reactant concentration affect the rate of CO2 production?" students react baking soda (sodium bicarbonate) with vinegar solutions of different concentrations. They prepare 50.0 mL of vinegar at 25%, 50%, and 100% strength (diluted with water), all at 22°C, in identical flasks. They add 2.00 g of sodium bicarbonate to each flask, quickly seal with a balloon, and measure the circumference of the balloon after 30 seconds. Which list contains only controlled variables (constants) for this investigation?
In a lab demo, a small piece of sodium (Na), a period 3, group 1 element, is kept in a jar under mineral oil. When exposed to water, Na reacts quickly and produces hydrogen gas. Which justification best explains why Na is stored under oil and reacts so vigorously with water?
Fluorine has electron configuration $1s^2\,2s^2\,2p^5$ and commonly forms F. Which change correctly describes the formation of F?
Neon (Ne) has electron configuration $1s^2\,2s^2\,2p^6$ and fluorine (F) has electron configuration $1s^2\,2s^2\,2p^5$ . Neon's first ionization energy is higher than fluorine's. Which electron-configuration-based reason best explains this?
A fusion reaction is shown: $^{2}_{1}\mathrm{H} + {}^{3}_{1}\mathrm{H} \rightarrow {}^{4}_{2}\mathrm{He} + {}^{1}_{0}\mathrm{n}.$ What particle is produced along with helium-4?
A student is designing a phone case for someone who works in a hair salon. The case may be exposed to hair dye, hydrogen peroxide developer, and alcohol-based disinfectant. It should not discolor, become sticky, or break down from these chemicals. Which chemical property is most important to match this environment?
Fluorine (F) and iodine (I) are both halogens (group 17). In a classroom demonstration, F reacts much more vigorously than I with a metal. Which justification best explains the difference using periodic trends and electron arrangement?
In the balanced equation $\mathrm{Zn + 2HCl \rightarrow ZnCl_2 + H_2},$ which statement correctly describes the mole relationship between $\mathrm{HCl}$ and $\mathrm{H_2}$ ?
Beryllium (Be, Group 2 Period 2), magnesium (Mg, Group 2 Period 3), and barium (Ba, Group 2 Period 6) are compared for how vigorously they react with water. Arrange them from least reactive to most reactive with water.
In a lab, a student heats solid potassium chlorate strongly. The solid only breaks down while the burner is on; when the heat is removed, the reaction stops. Which classification best fits this process based on the need for continuous energy input?
Many household smoke detectors contain a tiny amount of americium-241, which helps detect smoke and can save lives by providing early warning of fires. The radioactive material is sealed inside the device, but improper disposal or damage could create unnecessary exposure, so special disposal rules may apply. Which choice best balances benefits and risks of this nuclear technology?
Students test: "How does surface area affect the rate of reaction between calcium carbonate and hydrochloric acid?" They add 50.0 mL of 1.0 M HCl to each of three flasks at room temperature. In Trial 1 they add 5.0 g of CaCO3 powder, in Trial 2 they add 5.0 g of small chips, and in Trial 3 they add 5.0 g of one large chunk. They quickly place a balloon over the mouth of each flask and measure the balloon circumference after 60 seconds. Which factor is being deliberately changed between trials?
These elements are in period 2: lithium (Li) is in group 1, carbon (C) is in group 14, and fluorine (F) is in group 17. Which element is most electronegative?
An ice cube is placed on a plate in a warm room. Before, it is solid ice; after 10 minutes, there is a puddle of liquid water on the plate. What kind of change occurs?

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