HESI A2
HESI A2 Chemistry
1. What is the oxidation state of the oxygen atom in the compound NaOH?
- A. -2
- B. -1
- C. 0
- D. +2
Correct answer: B
Rationale: In the compound NaOH (sodium hydroxide), the oxidation state of the sodium ion (Na) is +1 as it commonly has a +1 charge in ionic compounds. Oxygen (O) typically has an oxidation state of -2 in most compounds. Since the compound is electrically neutral and the overall charge is zero, the sum of the oxidation states of all atoms in the compound must be zero. Therefore, considering that sodium has an oxidation state of +1, the oxygen atom in NaOH must have an oxidation state of -1 to balance the charges and overall neutrality of the compound. Choice A (-2) is incorrect as this is not the oxidation state of oxygen in this compound. Choice C (0) is incorrect as oxygen in NaOH does not have an oxidation state of 0. Choice D (+2) is incorrect as oxygen typically has a negative oxidation state in compounds, not a positive one.
2. Which organelle is responsible for generating energy within a cell?
- A. Nucleus
- B. Ribosome
- C. Mitochondria
- D. Golgi apparatus
Correct answer: C
Rationale: Mitochondria are commonly referred to as the powerhouses of the cell as they are primarily responsible for generating energy through cellular respiration. This process involves converting nutrients into adenosine triphosphate (ATP), which is the main energy currency of the cell. The nucleus is responsible for storing the cell's genetic material, the ribosome is involved in protein synthesis, and the Golgi apparatus is responsible for packaging and distributing molecules produced by the cell; therefore, they are not directly involved in energy generation.
3. A nurse needs to dilute 2 milliliters of a concentrated medication with 8 milliliters of sterile water. What is the final concentration of the solution in percent?
- A. 16.67%
- B. 20%
- C. 25%
- D. 50%
Correct answer: B
Rationale: To find the final concentration, first, calculate the total volume of the solution (2 ml + 8 ml = 10 ml). Then, determine the concentration by dividing the volume of the concentrated medication by the total volume and multiplying by 100%: (2 ml / 10 ml) * 100% = 20%. Therefore, the correct answer is B. Choice A (16.67%) is incorrect as it does not represent the correct calculation. Choices C (25%) and D (50%) are both incorrect as they do not reflect the accurate concentration resulting from the dilution process.
4. Which gland produces hormones that regulate sleep?
- A. Thyroid gland
- B. Pineal gland
- C. Adrenal gland
- D. Pituitary gland
Correct answer: B
Rationale: The pineal gland secretes melatonin, a hormone that plays a crucial role in regulating the sleep-wake cycle. Melatonin production is influenced by exposure to light, with levels increasing in the evening to promote sleep and decreasing in the morning to signal wakefulness. Choices A, C, and D are incorrect because the thyroid gland primarily regulates metabolism, the adrenal gland produces hormones like adrenaline and cortisol related to stress response, and the pituitary gland controls various functions by releasing different hormones but not specifically related to regulating sleep.
5. What is the author’s primary purpose in writing the essay about Concussions?
- A. To inform.
- B. To persuade.
- C. To entertain.
- D. To analyze.
Correct answer: D
Rationale: The primary purpose of the essay is to inform the reader about concussions, their effects, and recovery. While analysis may be involved in the presentation, the overarching goal is to provide information, making A the most accurate answer.
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