Nursing Elites

1. The molar mass of some gases is as follows: carbon monoxide—28.01 g/mol; helium—4.00 g/mol; nitrogen—28.01 g/mol; and oxygen—32.00 g/mol. Which would you expect to diffuse most rapidly?

• A. Carbon monoxide
• B. Helium
• C. Nitrogen
• D. Oxygen

Correct answer: B

Rationale: The rate of diffusion is inversely proportional to the molar mass of the gas. Helium has the lowest molar mass among the given gases, making it the lightest and fastest gas to diffuse. Therefore, helium would be expected to diffuse most rapidly compared to carbon monoxide, nitrogen, and oxygen. Carbon monoxide, nitrogen, and oxygen have higher molar masses than helium, so they would diffuse more slowly. Therefore, the correct answer is helium.

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. What is the oxidation state of the potassium ion in the compound KCl?

• A. +1
• B. -1
• C. +2
• D. -2

Correct answer: A

Rationale: In the compound KCl (potassium chloride), potassium is in Group 1 of the periodic table, which means it has a valence electron of 1. Chlorine is in Group 17 and gains one electron to achieve a stable electron configuration by forming an ionic bond with potassium. As a result, the potassium ion in KCl has a +1 oxidation state. Therefore, the correct answer is +1. Choices B, C, and D are incorrect as they do not reflect the oxidation state of the potassium ion in KCl.

4. What are mixtures of 2 or more metals called?

• A. Solutions
• B. Alloys
• C. Compounds
• D. Suspensions

Correct answer: B

Rationale: Alloys are mixtures of two or more metals, combining their properties to create materials with enhanced characteristics. Examples of alloys include bronze (copper and tin) and steel (iron and carbon). Alloys are commonly used in various industries due to their improved strength, durability, and other desirable qualities. Solutions (Choice A) refer to a homogeneous mixture of two or more substances, where one substance is dissolved in another. Compounds (Choice C) are substances composed of two or more elements chemically combined in fixed proportions. Suspensions (Choice D) are heterogeneous mixtures where particles are dispersed but can settle out over time.

5. Which two elements are most alike in reactivity?

• A. He and H
• B. K and Ar
• C. Cl and P
• D. Ba and Mg

Correct answer: C

Rationale: Chlorine (Cl) and Phosphorus (P) are most alike in reactivity among the given pairs. Both elements are nonmetals and belong to Group 7 (halogens) and Group 15 (nitrogen group), respectively. They have similar electronic configurations and can form compounds by gaining or sharing electrons. Chlorine is highly reactive and can easily form ionic compounds, while phosphorus also shows a range of reactivity in its compounds. Choice A (He and H) is incorrect because helium (He) is a noble gas and hydrogen (H) is a nonmetal, so they are not similar in reactivity. Choice B (K and Ar) is incorrect as potassium (K) is a metal and argon (Ar) is a noble gas, having different reactivities. Choice D (Ba and Mg) is incorrect because barium (Ba) and magnesium (Mg) are both metals, but their reactivities differ due to their positions in the periodic table.

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