Practice Test 23 - High School Chemistry

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

A team prototypes a refillable water bottle with a flip-top lid. Design 1 uses a polycarbonate plastic lid because it is tough and clear. In dishwasher tests (70–75°C) repeated daily for 3 weeks, the lid develops fine cracks near the hinge and becomes cloudy. No cracks appear when the lid is only hand-washed in cool water. Which refinement is most supported by the evidence?
Deuterium-deuterium reactions can be written as $^{2}_{1}\text{H} + {}^{2}_{1}\text{H} \rightarrow {}^{3}_{2}\text{He} + {}^{1}_{0}n.$ What process is shown by this equation?
A student mixes two solutions in a sealed flask and records the data below. Before mixing: - 50.0 mL of sodium carbonate solution, Na2CO3(aq): mass = 52.0 g, temperature = 22.0°C, appearance = clear, colorless - 50.0 mL of calcium chloride solution, CaCl2(aq): mass = 51.0 g, temperature = 22.0°C, appearance = clear, colorless After mixing (sealed flask): - Mixture: total mass = 103.0 g, temperature = 25.5°C, appearance = cloudy with a white solid What does the data indicate about whether a chemical reaction occurred?
A robotics club needs a lightweight metal bracket that will sometimes be splashed with weak vinegar solution during a demonstration. The bracket must keep its shape (stiffness important), should not corrode quickly, and must fit a limited budget. Which material is the best trade-off? Options: - Plain carbon steel: very stiff and cheap; rusts/corrodes readily when exposed to moisture and acids. - Aluminum alloy: lightweight; decent corrosion resistance to weak acids for short exposure; can pit over time; moderate cost. - Stainless steel: very good corrosion resistance; stiff; higher cost and heavier than aluminum.
A student notices that steel wool left damp in a plastic cup develops an orange-brown coating over several days. They want to test whether salt water speeds up rusting (a chemical change) compared with pure water. The result matters for deciding how to store metal tools near the ocean. Which investigation design best tests this question with clear variables, controls, and evidence collection?
A reaction is described as a chain reaction because neutrons released in one event can trigger additional events in nearby nuclei. This description most strongly matches which nuclear process?
Which set of coefficients balances the equation (smallest whole numbers)? C3H8 + O2 → CO2 + H2O
Two single-step reactions, A and B, have the same reactant and product energy levels, but reaction A has a higher peak than reaction B. Which statement is correct?
Determine the correct coefficients to balance the equation (smallest whole numbers): C3H8 + O2 → CO2 + H2O
A student opens a bottle of carbonated water. Immediately, bubbles rise to the surface and a hissing sound is heard. No temperature change, color change, or solid formation is observed. Which statement best describes whether the bubbling is evidence of a chemical reaction?
To answer the question How does the presence of a catalyst affect the decomposition rate of hydrogen peroxide? a student sets up two identical flasks, each containing 30.0 mL of 3% H $_2$ O $_2$ at 25°C. Flask 1 receives 0.50 g of manganese dioxide (MnO $_2$ ) and Flask 2 receives no solid. Each flask is connected to a gas syringe, and the student records the volume of O $_2$ produced after 60 seconds. What is being deliberately changed between the two flasks?
Students ask: How does water temperature affect the dissolving rate of sugar? They pour 100 mL of water into three identical beakers and adjust the water to 20C, 40C, and 60C using a hot plate and thermometer. They add 10.0 g of granulated sugar to each beaker, stir each solution at the same steady rate (about one stir per second), and record how many seconds it takes for all visible sugar crystals to disappear. What is being measured as the outcome (dependent variable)?
A school cafeteria tested a new biodegradable fork made from polylactic acid (PLA). PLA was selected because it is plant-based and compostable. In hot soup tests at $85^\circ\text{C}$ for 5 minutes, the fork bent and the tines deformed, but in cold foods it worked well. Which refinement best addresses the evidence while keeping the product compostable?
A chemical storeroom contains halogens fluorine (F, period 2), chlorine (Cl, period 3), bromine (Br, period 4), and iodine (I, period 5). Reactivity of halogens changes predictably down Group 17. Which halogen is most reactive?
In another displacement test, bromine (Br $_2$ , Group 17 period 4) is added to a solution of potassium iodide (KI), which contains iodide ions from iodine (I, period 5). Will bromine displace iodine from potassium iodide?
A student leaves a piece of steel wool on a damp paper towel overnight. By the next day, the steel wool has changed from gray to reddish-brown in several spots, and the surface looks rough and flaky. Which observation best indicates new substances formed?
A student adds a spoonful of baking soda to a cup of vinegar. The mixture immediately fizzes, a stream of bubbles rises from the liquid, and the cup feels cooler to the touch after about 30 seconds. Which observation is evidence that a chemical reaction occurred (new substances formed)?
A student mixes sodium bicarbonate (NaHCO $_3$ ) and vinegar (aqueous acetic acid) in an open cup. The student measures mass and temperature before and after mixing. Data: - Before mixing: 5.00 g NaHCO $_3$ (solid, white) + 50.0 g vinegar (clear liquid), temperature 22.0°C - Immediately after mixing stops fizzing: cup contents mass = 52.80 g, temperature 18.5°C, appearance = clear liquid with bubbles during mixing Which interpretation best fits the data?
Consider the balanced equation: $N_2 + 3H_2 \rightarrow 2NH_3$ If $6.0\ \text{mol}$ of $H_2$ react completely, how many moles of $NH_3$ are produced?
Sodium (Na), silicon (Si), and chlorine (Cl) are all in period 3. Na is in group 1, Si is in group 14, and Cl is in group 17. Which element has the smallest atomic radius?

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