HESI A2
Chemistry HESI A2 Quizlet
1. Which particles are emitted during radioactivity?
- A. Electrons
- B. Protons
- C. Radiation
- D. Neutrons
Correct answer: C
Rationale: During radioactivity, radiation is emitted from an unstable nucleus. This radiation can take various forms like alpha particles, beta particles, or gamma rays. These particles or rays are emitted as a result of the unstable nucleus's attempt to achieve a more stable configuration. Therefore, the correct answer is radiation (Choice C). Electrons (Choice A), protons (Choice B), and neutrons (Choice D) are not typically emitted during radioactivity, as the emission is primarily in the form of radiation.
2. Which factor does not affect the reaction rate of a chemical reaction?
- A. Temperature
- B. Surface area
- C. Concentration of reactants
- D. Color of the reactants
Correct answer: D
Rationale: The color of reactants is not a factor that affects the rate of a chemical reaction. Temperature, surface area, and concentration of reactants are known factors that influence the reaction rate. Temperature plays a significant role in altering the reaction rate by affecting the kinetic energy of molecules. Surface area impacts the rate by providing more area for collisions to occur. Concentration affects the frequency of effective collisions. On the other hand, the color of reactants is a physical property that does not directly affect the speed of a chemical reaction.
3. Radioactive isotopes are frequently used in medicine. What kind of half-life would a medical isotope probably have?
- A. Seconds-long
- B. Days-long
- C. Years-long
- D. Many years long
Correct answer: B
Rationale: Medical isotopes used in diagnosis and treatment need to have a relatively short half-life to minimize radiation exposure to patients. If the half-life were too long (such as many years) or even years-long, the radiation would persist for too long and could be harmful to the patient. Seconds-long half-lives would not provide enough time for the isotope to be effective. Days-long half-lives strike a balance between providing enough time for the isotope to be used effectively and minimizing radiation exposure.
4. What type of reactions take place in the nucleus to achieve stable nuclear configurations?
- A. Chemical
- B. Nuclear
- C. Physical
- D. Mechanical
Correct answer: B
Rationale: Nuclear reactions occur within the nucleus to achieve stable nuclear configurations. These reactions involve changes in the composition of atomic nuclei, leading to the formation of more stable elements. Chemical reactions occur in the electron cloud surrounding the nucleus, while physical and mechanical processes do not directly impact the stability of nuclear configurations. Therefore, the correct answer is 'Nuclear.'
5. How many neutrons are in an atom of carbon-12?
- A. 2
- B. 4
- C. 6
- D. 24
Correct answer: C
Rationale: An atom of carbon-12 has 6 neutrons. The atomic number of carbon is 6, representing the number of protons. The atomic mass of carbon-12 is 12. To find the number of neutrons, subtract the atomic number from the atomic mass: 12 - 6 = 6 neutrons. Choice A, 2, is incorrect as it does not reflect the correct calculation for neutrons in carbon-12. Choice B, 4, is incorrect as it does not match the correct number of neutrons in carbon-12. Choice D, 24, is incorrect as it is significantly higher than the actual number of neutrons in carbon-12.
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