Which of the following is a characteristic of a chemical reaction?
Change in color
Formation of a precipitate
Release of gas
Change in temperature
All of the above
The Correct Answer is E
Choice A reason: A color change during a chemical reaction indicates the formation of new substances with altered molecular structures, affecting light absorption. For instance, iron reacting with oxygen forms iron oxide, shifting from silver to reddish-brown. This reflects a chemical transformation where new compounds with distinct optical properties are produced, confirming a reaction at the molecular level.
Choice B reason: Precipitate formation signifies a chemical reaction as soluble reactants produce an insoluble solid. In a double displacement reaction, such as silver nitrate combining with sodium chloride, silver chloride precipitates. This occurs due to ion exchange, forming a new compound with low solubility, providing visible evidence of a chemical change driven by molecular restructuring.
Choice C reason: Gas release during a reaction indicates a chemical change, as new gaseous products form from reactants. For example, sodium bicarbonate reacting with acetic acid produces carbon dioxide gas. This results from molecular bond rearrangement, where reactants break and reform into new molecules, including a gas, confirming a chemical transformation.
Choice D reason: Temperature changes often accompany chemical reactions, reflecting energy shifts. Exothermic reactions, like combustion, release heat, increasing temperature, while endothermic reactions absorb heat, decreasing it. These changes occur as chemical bonds break and form, redistributing energy. This energy dynamic is a hallmark of chemical reactions, indicating molecular-level transformations.
Choice E reason: This choice is correct as all listed signs—color change, precipitate formation, gas release, and temperature change—are indicators of chemical reactions. Each reflects molecular rearrangements, such as new compound formation or energy shifts. By encompassing all these observable phenomena, this option accurately represents the diverse physical manifestations of chemical changes.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A reason: Serum lithium levels indicate compliance but do not directly explain the need for frequent monitoring. Lithium’s therapeutic effect stabilizes mood, but monitoring is primarily due to its narrow therapeutic index, where small changes in blood levels can cause toxicity, not just behavioral changes or compliance.
Choice B reason: Sodium levels affect lithium excretion, as both compete for renal reabsorption. Low sodium increases lithium retention, risking toxicity, while high sodium increases excretion, reducing efficacy. Lithium’s narrow therapeutic range (0.6–1.2 mEq/L) necessitates frequent monitoring to prevent toxic levels, which can cause neurological or cardiac issues.
Choice C reason: Myelosuppression and agranulocytosis are not common lithium side effects. Lithium may cause mild leukocytosis, not suppression. Toxicity risks, like neurological or renal effects, drive monitoring needs, not hematologic issues. This choice is incorrect, as it misrepresents lithium’s side effect profile.
Choice D reason: Tyramine, relevant to monoamine oxidase inhibitors, does not influence lithium metabolism. Lithium’s pharmacokinetics are affected by sodium and renal function, not dietary tyramine. This choice is incorrect, as it falsely links a dietary factor to lithium’s monitoring requirements.
Correct Answer is A
Explanation
Choice A reason: Range of motion assesses muscle relaxant effectiveness, as these drugs, like cyclobenzaprine, reduce muscle spasms by acting on the central nervous system, relieving pain and improving mobility. Increased leg movement indicates reduced spasm and pain, directly reflecting the drug’s therapeutic action.
Choice B reason: Capillary refill evaluates perfusion, not muscle relaxation. Muscle relaxants target spasms, not vascular status. While pain may indirectly affect circulation, capillary refill does not measure the drug’s primary effect on muscle function, making this choice irrelevant.
Choice C reason: Dependent edema reflects fluid status, not muscle relaxant efficacy. These drugs reduce muscle tension, not swelling. Edema is unrelated to leg pain from spasms, and muscle relaxants do not affect fluid dynamics, making this choice inappropriate for assessment.
Choice D reason: Skin temperature may indicate inflammation or circulation but is not specific to muscle relaxant effects. These drugs alleviate spasms, improving mobility, not temperature. Range of motion directly measures spasm relief, making this choice less relevant for evaluating the medication’s impact.
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