Nursing Elites

1. The number of protons in an atom determines its:

• A. Mass number
• B. Atomic number
• C. Atomic weight
• D. Valence electron count

Correct answer: B

Rationale: The number of protons in an atom is known as the atomic number. The atomic number uniquely identifies an element and determines its position on the periodic table. It is a fundamental property of an element and directly influences its chemical behavior and interactions. The mass number, on the other hand, is the sum of protons and neutrons in the nucleus of an atom, not just protons. Atomic weight is the average mass of an element's isotopes considering their relative abundance, not solely based on the number of protons. Valence electron count refers to the number of electrons in the outermost energy level of an atom, influencing its ability to form bonds and participate in chemical reactions, but it is not determined by the number of protons in the atom.

2. During which of the following stages does crossing over occur?

• A. Mitosis Prophase
• B. Meiosis Prophase I
• C. Meiosis Prophase II
• D. Interphase

Correct answer: B

Rationale: Crossing over occurs during Prophase I of meiosis. This stage is specifically associated with genetic recombination, where homologous chromosomes exchange genetic material. This process contributes to genetic diversity by creating new combinations of alleles. Choices A, C, and D are incorrect. In mitosis, crossing over does not occur as it involves the separation of replicated chromosomes. Meiosis Prophase II is focused on the reformation of nuclei and does not involve crossing over. Interphase is a stage where the cell prepares for division and is not associated with crossing over.

3. Which statement accurately defines power?

• A. Power is the amount of energy stored in an object
• B. Power is the rate at which energy is transferred or work is done
• C. Power is the maximum force exerted by an object
• D. Power is the resistance of an object to change in motion

Correct answer: B

Rationale: Power is defined as the rate at which energy is transferred or work is done. It is a measure of how quickly work is done or energy is transferred. Option A incorrectly refers to the amount of energy stored in an object, not power. Option C incorrectly refers to the maximum force exerted by an object, not power. Option D incorrectly refers to the resistance of an object to change in motion, not power. Therefore, the correct definition of power is that it is the rate at which energy is transferred or work is done.

4. 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.

5. A rocket engine expels hot gases backwards. What principle explains the rocket's forward motion?

• A. Newton's first law of motion
• B. Newton's second law of motion
• C. Newton's third law of motion
• D. Law of conservation of energy

Correct answer: C

Rationale: Newton's third law of motion states that for every action, there is an equal and opposite reaction. In the case of a rocket engine expelling hot gases backwards, the action is the expulsion of gases, and the reaction is the forward motion of the rocket. The hot gases being expelled act as the action force, propelling the rocket in the opposite direction as the reaction force, resulting in the rocket's forward motion. Newton's first law of motion (Choice A) pertains to inertia, stating that an object in motion will stay in motion unless acted upon by an external force. Newton's second law of motion (Choice B) relates force, mass, and acceleration, which is not directly applicable to the scenario of a rocket engine propulsion. The law of conservation of energy (Choice D) is a fundamental principle stating that energy cannot be created or destroyed but can only be transformed, which does not directly explain the forward motion of the rocket in this context.

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