HESI A2
HESI A2 Chemistry Questions
1. Which gas is released during photosynthesis?
- A. Carbon dioxide
- B. Oxygen
- C. Nitrogen
- D. Helium
Correct answer: B
Rationale: During photosynthesis, plants utilize carbon dioxide and water to produce glucose and oxygen. Oxygen is released as a byproduct of this process, which is essential for the survival of most living organisms that depend on it for respiration. Therefore, the correct answer is oxygen. Choices A, C, and D are incorrect. Carbon dioxide is utilized in photosynthesis, nitrogen is not directly involved in the process, and helium is not a gas released during photosynthesis.
2. What can stop the penetration of gamma radiation?
- A. Aluminum foil
- B. Glass
- C. Several feet of concrete
- D. Piece of paper
Correct answer: C
Rationale: Gamma radiation is highly penetrative and requires dense materials to block it effectively. While aluminum foil and glass are not sufficient to stop gamma radiation, several feet of concrete is needed due to its high density and ability to absorb gamma radiation effectively. A piece of paper is too thin and lacks the density required to block gamma radiation, making it an ineffective shield.
3. What is the term used when an atom gains one or more electrons?
- A. Cation
- B. Anion
- C. Isotope
- D. Electron
Correct answer: B
Rationale: When an atom gains electrons, it becomes negatively charged and is called an anion. An anion is formed when an atom gains one or more electrons, leading to an excess of negative charge. Choice A, 'Cation,' is incorrect because a cation is formed when an atom loses electrons, resulting in a positively charged ion. Choice C, 'Isotope,' refers to atoms of the same element with different numbers of neutrons and is not related to gaining electrons. Choice D, 'Electron,' is the particle that an atom gains to become an anion, not the term for the atom itself after gaining electrons.
4. What is the correct electron configuration for lithium?
- A. 1s²2s¹
- B. 1s²2s²
- C. 1s²2s¹2p¹
- D. 1s¹2s¹2p²
Correct answer: A
Rationale: The electron configuration for lithium is 1s²2s¹. Lithium has 3 electrons, and the configuration indicates that the first two electrons fill the 1s orbital, while the third electron fills the 2s orbital. Therefore, the correct electron configuration for lithium is 1s²2s¹. Choice B (1s²2s²) is incorrect as it represents the electron configuration for beryllium, not lithium. Choice C (1s²2s¹2p¹) includes the 2p orbital, which is not involved in lithium's electron configuration. Choice D (1s¹2s¹2p²) is incorrect as it does not accurately represent lithium's electron configuration.
5. What is the SI unit of energy?
- A. ohm
- B. joule
- C. henry
- D. newton
Correct answer: B
Rationale: The SI unit of energy is the 'joule'. The joule is defined as the work done when a force of one newton acts over a distance of one meter. It is the standard unit used to measure energy in the International System of Units (SI). Therefore, the correct answer is 'joule.' Choice A, 'ohm,' is the SI unit of electrical resistance, not energy. Choice C, 'henry,' is the SI unit of inductance, not energy. Choice D, 'newton,' is the SI unit of force, not energy. Hence, they are all incorrect in the context of measuring energy.
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