Nursing Elites

1. What is the main component of air?

• A. Oxygen
• B. Nitrogen
• C. Carbon dioxide
• D. Argon

Correct answer: B

Rationale: Nitrogen is the main component of air, constituting approximately 78% of the Earth's atmosphere. Oxygen, carbon dioxide, and argon are also present in smaller amounts, but nitrogen is the most abundant gas in the air. Therefore, the correct answer is B. Choice A, oxygen, is essential for respiration but makes up only about 21% of the atmosphere. Choice C, carbon dioxide, is vital for photosynthesis but exists in trace amounts in the air. Choice D, argon, is a noble gas found in relatively small quantities in the atmosphere.

2. What type of chemical reaction is represented by AB → A + B?

• A. Synthesis
• B. Decomposition
• C. Single replacement
• D. Double replacement

Correct answer: B

Rationale: The chemical equation AB → A + B represents a decomposition reaction. In a decomposition reaction, a single compound breaks down into two or more simpler substances. In this specific reaction, compound AB is decomposed into its elements, A and B, making it a decomposition reaction. Choice A, Synthesis, involves the combination of two or more substances to form a more complex product, which is not the case here. Choices C and D, Single replacement and Double replacement, involve the exchange of ions between compounds or elements, which is not happening in the given reaction.

3. If fifty-six kilograms of a radioactive substance has a half-life of 12 days, how many days will it take the substance to decay naturally to only 7 kilograms?

• A. 8
• B. 12
• C. 36
• D. 48

Correct answer: C

Rationale: To decay from 56 kg to 7 kg, the substance needs to go through 3 half-lives (56 kg ÷ 2 ÷ 2 ÷ 2 = 7 kg). Since each half-life is 12 days, the total time required is 12 days per half-life x 3 half-lives = 36 days. Choice A is incorrect because it does not consider the concept of half-lives. Choice B is incorrect because it represents the duration of a single half-life, not the total time required for the decay. Choice D is incorrect as it does not account for the multiple half-lives needed for the substance to decay from 56 kg to 7 kg.

4. You contain two odorous gases in vials with porous plugs. Gas A has twice the mass of Gas B. Which observation is most likely?

• A. You will smell Gas A before you smell Gas B.
• B. You will smell Gas B before you smell Gas A.
• C. You will smell Gas A but not Gas B.
• D. You will smell Gas B but not Gas A.

Correct answer: A

Rationale: The rate of effusion of a gas is inversely proportional to the square root of its molar mass. Since Gas A has twice the mass of Gas B, Gas A will effuse more slowly than Gas B. Therefore, you will likely smell Gas A before you smell Gas B as Gas A will escape and diffuse through the porous plug at a slower rate compared to Gas B. Choice A is correct because Gas A, with its higher molar mass, will take longer to effuse through the porous plug, causing you to smell it first. Choices B, C, and D are incorrect as they do not consider the relationship between molar mass and effusion rate.

5. Which one does not name a polar molecule?

• A. NH₃
• B. H₂S
• C. SO₂
• D. CO₂

Correct answer: A

Rationale: The correct answer is NH₃. The molecule NH₃ does not represent a polar molecule because nitrogen and hydrogen in this molecule have a small difference in electronegativity that does not result in a significant polar covalent bond. In contrast, molecules H₂S, SO₂, and CO₂ have polar covalent bonds due to larger electronegativity differences, making them polar molecules. Therefore, options B, C, and D are polar molecules, unlike option A.

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