Practice Test 16 - High School Chemistry

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

Balance the equation using the smallest whole-number coefficients: Zn + HCl → ZnCl2 + H2
Consider these processes: burning wood in a fireplace (chemical), a phone battery powering a device (chemical), radioactive decay in a radioisotope battery (nuclear), and fusion in the Sun (nuclear). Which option correctly orders them from least to most energy released per event (per atom/reaction)? (Recall: chemical reactions are typically eV-scale; nuclear processes are typically MeV-scale.)
A science class is selecting a container for a hydrogen peroxide solution used in demonstrations (not very concentrated). Requirements: (1) container should not speed up decomposition of hydrogen peroxide, (2) must be safe and practical for students, (3) should be reasonably durable and not too expensive. Which is the best trade-off? Materials: - Clear glass: generally inert; but lets light in, which can speed peroxide breakdown; breaks if dropped. - Amber (brown) plastic (HDPE): blocks light; durable; good compatibility; but can slowly absorb odors and may scratch. - Copper container: durable; but copper can catalyze peroxide decomposition (speeds it up).
Which statement correctly compares energy changes for bond breaking and bond forming in a chemical reaction?
Hydrogen chloride can form by: $\text{H}_2 + \text{Cl}_2 \rightarrow 2\text{HCl}$ If you start with $1.0\,\text{mol}$ of $\text{H}_2$ and $3.0\,\text{mol}$ of $\text{Cl}_2$ , what is the maximum amount of $\text{HCl}$ that can form (in moles)?
An aquarium club is building a small CO $_2$ injection system that uses carbonic acid (mildly acidic water) and must not contaminate fish. Requirements: non-toxic to aquatic life (critical), good corrosion resistance in mildly acidic water, and low cost. Materials: - Copper tubing: easy to bend; can release copper ions (toxic to fish); good thermal conductivity; moderate cost. - PVC tubing: chemically resistant; non-toxic for aquarium use; can soften if exposed to high heat (not expected here); low cost. - Brass fitting: durable; may leach small amounts of metals; moderate cost.
To answer the question How does stirring affect the rate at which salt dissolves?, students add 5.0 g of table salt (NaCl) to 100 mL of water at 25C in three identical beakers. Beaker A is not stirred, Beaker B is stirred slowly (about 1 круг per second), and Beaker C is stirred quickly (about 3 кругs per second). They start a timer when salt is added and stop it when all visible solid disappears. Which is the independent variable?
A student mixes 50 mL of a blue solution with 50 mL of a yellow solution in a beaker. Observations: - The mixture becomes green immediately. - The temperature remains 22.0°C before and after mixing. - No bubbles form. - No solid forms, even after sitting 10 minutes. - When the student separates the mixture using a simple paper chromatography strip, two distinct color bands (blue and yellow) appear. Based on the evidence, is there sufficient evidence to conclude a chemical reaction occurred? Choose the best CER-style justification.
Nuclear technology can be used to generate electricity in reactors, but similar knowledge and materials can also contribute to nuclear weapons programs. Electricity generation can provide reliable, low-CO2 power, while weapons proliferation raises global security risks. Which statement best balances these issues without being one-sided?
A student notices that a steel wool pad left near a classroom sink turns reddish-brown after a few days. Another student claims it is just dirt sticking to the metal (physical change), not rusting (chemical change). The class must design an investigation to test whether the color change is due to a chemical reaction with oxygen and water. Which experiment design best tests this claim with clear variables and controls?
A uranium-238 nucleus becomes thorium-234 by emitting an alpha particle (a helium nucleus). Which type of nuclear process is described?
A patient with thyroid cancer is offered radioactive iodine therapy. The benefit is that the iodine tends to concentrate in thyroid tissue, helping destroy cancer cells. Risks include temporary side effects and radiation exposure, so dosing and safety instructions (like limiting close contact for a short time) are used. Which statement best evaluates this trade-off?
Element A is sodium (Na), period 3 group 1, with electron configuration [Ne]3s1. Element B is potassium (K), period 4 group 1, with electron configuration [Ar]4s1. Potassium has a lower first ionization energy than sodium. Which feature of the electron configurations best explains this trend?
An ice cube is placed on a plate at room temperature. After 10 minutes, a puddle of liquid water forms where the ice cube was. Is this change physical or chemical? Choose the best answer based on the observations.
Fluorine (F), chlorine (Cl), and bromine (Br) are all in group 17 (the halogens). They commonly form \u22121 ions in ionic compounds. Why do these elements tend to form \u22121 ions?
An unstable nucleus emits an alpha particle (a helium nucleus) and becomes a different element with a smaller nucleus. Which type of nuclear process is described?
A student designed a copper wire sensor to be used in a saltwater (NaCl) aquarium to measure conductivity. Copper was chosen because it conducts electricity well. After 1 month, the copper wire turned green in spots, the measured conductivity drifted over time, and fish health concerns were raised. Which refinement best addresses the chemical issue indicated by the evidence?
A student adds water to quicklime (calcium oxide) in a beaker. The beaker becomes noticeably warm and the temperature of the mixture increases from 20°C to 45°C. Which description best matches what happened?
A team designed a refillable hand-sanitizer bottle with a rubber gasket to prevent leaks. The sanitizer is about 70% ethanol. They chose natural rubber for the gasket because it was flexible and cheap. After 3 weeks, the gasket swelled, became sticky, and the cap began leaking. Which refinement best matches the test evidence?
A student drops a small piece of magnesium ribbon into a cup containing an acid solution. The ribbon rapidly produces bubbles, gets smaller until it disappears, and the cup feels warm. What evidence indicates a chemical change occurred? (Select the best answer.)

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