Practice Test 27 - High School Chemistry

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

A student investigated how the amount of reactant affects the amount of gas produced. Different masses of sodium bicarbonate (NaHCO $_3$ ) were added to excess vinegar in identical flasks. The total CO $_2$ collected after 60 s was measured.
Mass of NaHCO $_3$ (g) CO $_2$ collected in 60 s (mL)

0.50 115
1.00 230
1.50 345
2.00 460
Which statement best describes the relationship between mass of NaHCO $_3$ and CO $_2$ volume collected (within this tested range)?
Cake batter is poured into a pan and baked in an oven. After baking, it becomes a solid cake with a different color, a new smell, and a different texture than the batter. Which type of change occurred?
In a lab, students observe that a reaction between two aqueous solutions proceeds faster when the solutions are more concentrated. One group plans to repeat the reaction by doubling the concentration of one reactant solution while keeping temperature and total volume the same. Which prediction best matches collision theory?
Hydrogen chloride forms by the reaction $\,H_2 + Cl_2 \rightarrow 2HCl\,$ . If 1.0 mol $H_2$ and 3.0 mol $Cl_2$ are available, what is the maximum amount of $HCl$ that can form?
What is the coefficient of O2 when the equation is balanced with the smallest whole numbers? Al + O2 → Al2O3
Balance the chemical equation using the smallest whole-number coefficients: Zn + HCl → ZnCl2 + H2
Calcium carbonate decomposes when heated: $\text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g)$ A student heats 25 g of $\text{CaCO}_3$ in an open crucible. After heating, 14 g of solid $\text{CaO}$ remains in the crucible. Which statement best accounts for the missing mass?
A concentration-versus-time graph for reactant $H$ shows a smooth decrease that is steep at first and then becomes gentler. Which statement best describes how the reaction rate changes as the reaction proceeds? Axes: y = concentration of $[H]$ (arbitrary units), x = time (s).
A very heavy nucleus breaks apart into two medium-sized nuclei and releases extra neutrons that can trigger more splitting events. Which process is described?
A custodian warns students not to mix a bathroom cleaner labeled "contains sodium hypochlorite (bleach)" with a toilet bowl cleaner labeled "contains acid." The students want to investigate (safely, in tiny amounts and with teacher approval) whether mixing a dilute bleach solution with a dilute acidic solution produces evidence of a chemical reaction. Which investigation design best tests the question with clear variables, controlled conditions, and observable evidence?
Use the periodic trend for atomic radius. Consider these elements: - Li (period 2, group 1) - Al (period 3, group 13) - K (period 4, group 1) Which element has the largest atomic radius?
A nucleus undergoes beta decay: $^{131}_{53}\text{I} \rightarrow X + {}^{0}_{-1}e.$ What is the product nucleus $X$ ?
A team designs a clear protective cover for an outdoor sensor. Design 1 uses a clear polystyrene sheet because it is inexpensive and easy to cut. After 2 months in direct sunlight, the cover turns yellow and becomes brittle, cracking during a light bend test. An identical cover kept indoors stays clear and flexible. Which refinement best uses the evidence to improve the design for outdoor use?
A country considers expanding nuclear energy to reduce air pollution and carbon emissions from fossil fuels. Nuclear plants can provide steady electricity with low greenhouse gas emissions during operation and require relatively small amounts of fuel. Concerns include high construction and decommissioning costs, long-lived radioactive waste, and the possibility that nuclear materials or expertise could be diverted toward weapons programs. Which statement best balances these considerations?
A janitor finds two unlabeled white powders in the supply room. One might be baking soda (sodium bicarbonate) and the other might be powdered sugar. For safety, the janitor needs to know whether either powder undergoes a chemical change when mixed with vinegar (acetic acid). Design an investigation to answer: Which powder reacts chemically with vinegar? Which experimental plan is best?
Table salt (sodium chloride, NaCl) has a much higher melting point than either sodium metal or chlorine gas. Which justification best connects the periodic table positions of Na (group 1) and Cl (group 17) to this property of NaCl?
In the balanced combustion equation $\mathrm{CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O}$ what is the mole ratio of $\mathrm{O_2}$ to $\mathrm{CH_4}$ ?
A student claims that mixing two clear solutions—calcium chloride solution and sodium carbonate solution—might or might not be a chemical change because "they're both just salts in water." The class needs to design an experiment to confirm whether a chemical reaction occurs. Which investigation design is best?
A piece of dry ice is placed on a lab table. Over time it gets smaller and a fog-like vapor appears around it, and eventually the solid disappears without leaving a liquid puddle. What kind of change is this?
Iron (Fe) filings are mixed with sulfur (S) powder in a test tube. Data: - Before heating: 2.00 g Fe (gray solid) + 1.00 g S (yellow solid), temperature 22°C - After strong heating and cooling: 3.00 g solid, black, not attracted to a magnet, temperature 22°C Which data point is the best evidence that a new substance formed?

Mass of NaHCO $_3$ (g)	CO $_2$ collected in 60 s (mL)
0.50	115
1.00	230
1.50	345
2.00	460

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