Nursing Elites

1. In a single displacement reaction, one element takes the place of another element in a compound. Which of the following is an example?

• A. 2H2 + O2 -> 2H2O
• B. Zn + 2HCl -> ZnCl2 + H2
• C. CaCO3 -> CaO + CO2
• D. CH4 + 2O2 -> CO2 + 2H2O

Correct answer: B

Rationale: Option B demonstrates a single displacement reaction where zinc (Zn) displaces hydrogen (H) in hydrochloric acid (HCl) to produce zinc chloride (ZnCl2) and hydrogen gas (H2). This reaction exemplifies the concept of one element (Zn) replacing another element (H) in a compound (HCl), which is characteristic of single displacement reactions. Choices A, C, and D do not involve a single element displacing another in a compound, making them incorrect. In choice A, hydrogen and oxygen combine to form water, which is not a single displacement reaction. In choice C, calcium carbonate decomposes into calcium oxide and carbon dioxide, not involving displacement of elements. In choice D, methane reacts with oxygen to form carbon dioxide and water, which is a combustion reaction, not a single displacement reaction.

2. How many moles of water are produced when 0.5 moles of methane (CH4) react with excess oxygen?

• A. 0.5 moles
• B. 1 mole
• C. 2 moles
• D. 3 moles

Correct answer: B

Rationale: The balanced chemical equation for the combustion of methane is: CH4 + 2O2 -> CO2 + 2H2O. This equation shows that 1 mole of methane produces 2 moles of water. Therefore, when 0.5 moles of methane react, they will produce 1 mole of water. The ratio of water to methane is 2:1, meaning that for every mole of methane that reacts, it produces 2 moles of water. Since only 0.5 moles of methane are reacting, the amount of water produced will be half of what would be produced if 1 mole of methane reacted, resulting in 1 mole of water being produced. Choice A is incorrect because it does not consider the stoichiometry of the reaction. Choices C and D are incorrect as they do not align with the balanced chemical equation and the stoichiometric ratios involved in the reaction.

3. What is the unit of measurement for density?

• A. Grams per liter (g/L)
• B. Kilograms per cubic meter (kg/m³)
• C. Pounds per square inch (psi)
• D. Newtons per meter (N/m)

Correct answer: A

Rationale: Density is defined as mass per unit volume. The most commonly used unit for density in the metric system is grams per liter (g/L). Kilograms per cubic meter (kg/m³) is also a common unit for density, but grams per liter is more frequently used in everyday measurements. Pounds per square inch (psi) is a unit of pressure, not density. Newtons per meter (N/m) is a unit of force per unit length, not density.

4. Which vitamin is essential for calcium absorption and bone health?

• A. Vitamin A
• B. Vitamin C
• C. Vitamin D
• D. Vitamin E

Correct answer: C

Rationale: Vitamin D is essential for calcium absorption in the intestines, which is crucial for maintaining strong and healthy bones. Without adequate vitamin D, the body cannot effectively absorb calcium, leading to weakened bones and an increased risk of fractures. Vitamin A (Choice A) is important for vision and immune function but is not directly involved in calcium absorption or bone health. Vitamin C (Choice B) is essential for collagen synthesis and immune function, but it does not play a direct role in calcium absorption or bone health. Vitamin E (Choice D) acts as an antioxidant and helps protect cells from damage, but it is not specifically required for calcium absorption or bone health. Therefore, the correct answer is Vitamin D as it is crucial for optimal bone health.

5. Which cells myelinate neurons in the PNS?

• A. Oligodendrocytes
• B. Astrocytes
• C. Schwann cells
• D. Microglia

Correct answer: C

Rationale: Schwann cells are the glial cells responsible for myelinating neurons in the peripheral nervous system (PNS). They form the myelin sheath around axons, which helps in the conduction of electrical impulses. Oligodendrocytes, on the other hand, myelinate neurons in the central nervous system (CNS). Astrocytes primarily provide support for neuronal function by regulating the chemical environment around neurons and maintaining the blood-brain barrier. Microglia are part of the immune response in the CNS, where they act as the resident macrophages, playing a role in immune surveillance and response to injury or disease. Therefore, the correct answer is Schwann cells (Choice C) as they specifically myelinate neurons in the PNS, differentiating them from the other cell types mentioned in the choices.

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