Nursing Elites

1. What type of bond is present in sodium chloride?

• A. Covalent
• B. Ionic
• C. Metallic
• D. Hydrogen

Correct answer: B

Rationale: Ionic bonds are found in sodium chloride. In an ionic bond, one atom donates an electron to another atom, resulting in the formation of positively and negatively charged ions that are held together by electrostatic forces of attraction. Sodium chloride is a classic example of an ionic compound, where sodium (Na) donates an electron to chlorine (Cl), forming Na+ and Cl- ions that are attracted to each other, creating a crystal lattice structure. Covalent bonds involve the sharing of electron pairs between atoms, which is not the case in sodium chloride. Metallic bonds occur in metals where electrons are delocalized and shared across a lattice, unlike the specific transfer seen in ionic bonds. Hydrogen bonds are a type of intermolecular force, not the primary bond type present in sodium chloride.

2. A radioactive isotope has a half-life of 20 years. How many grams of a 6-gram sample will remain after 40 years?

• A. 8
• B. 6
• C. 3
• D. 1.5

Correct answer: C

Rationale: The half-life of a radioactive isotope is the time it takes for half of the original sample to decay. After each half-life period, half of the initial sample remains. In this case, after the first 20 years, half of the 6-gram sample (3 grams) will remain. After another 20 years (total of 40 years), half of the remaining 3 grams will remain, which is 1.5 grams. Therefore, 3 grams will be left after 40 years. Choice A is incorrect as it doesn't consider the concept of half-life and incorrectly suggests an increase in the sample. Choice B is incorrect as it assumes no decay over time. Choice D is incorrect as it miscalculates the remaining amount after two half-life periods.

3. Which chemical reaction involves the formation of a single product from two or more reactants?

• A. Synthesis reaction
• B. Combustion reaction
• C. Decomposition reaction
• D. Double displacement reaction

Correct answer: A

Rationale: A synthesis reaction involves the combination of two or more reactants to form a single product. This type of reaction is characterized by the merging of substances to create a more complex compound. In a synthesis reaction, the reactants bond together to form a new product, making it the correct choice for this scenario. Combustion reactions involve the rapid combination of oxygen with another substance, resulting in the release of energy in the form of heat and light. Decomposition reactions entail the breakdown of a compound into simpler substances, often through the application of heat or electricity. Double displacement reactions involve the exchange of ions between two compounds, leading to the formation of two new compounds.

4. Which of these types of intermolecular force is the strongest?

• A. Dipole-dipole interaction
• B. London dispersion force
• C. Keesom interaction
• D. Hydrogen bonding

Correct answer: D

Rationale: Hydrogen bonding is the strongest type of intermolecular force among the options provided. It occurs when a hydrogen atom is covalently bonded to a highly electronegative atom (such as nitrogen, oxygen, or fluorine) and forms a strong electrostatic attraction with an unshared pair of electrons on another electronegative atom. This type of bond is stronger than dipole-dipole interactions, London dispersion forces, and Keesom interactions due to the significant electronegativity difference between the hydrogen and the electronegative atom involved in the bond. The presence of hydrogen bonding contributes to unique properties in substances, such as high boiling and melting points, making it a crucial force in various biological and chemical processes.

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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