Nursing Elites

1. Which of the following is a characteristic of a chemical change?

• A. Change in shape
• B. Production of gas
• C. Melting
• D. Freezing

Correct answer: B

Rationale: The production of gas is a characteristic of a chemical change. During a chemical change, new substances are formed, often with the release or absorption of energy. The production of gas is a significant indicator of a chemical change because it indicates the formation of new compounds through chemical reactions. Choices A, C, and D are not characteristics of chemical changes. Changes in shape, melting, and freezing are physical changes where the substance's identity remains the same, unlike in chemical changes where new substances with different properties are formed.

2. What is the name of the bond formed when two atoms share electrons?

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

Correct answer: A

Rationale: A covalent bond is formed when two atoms share electrons, creating a stable electron configuration. This sharing allows both atoms to achieve a full outer shell of electrons, leading to a stable molecule. In contrast, an ionic bond involves the transfer of electrons from one atom to another, resulting in the formation of ions with opposite charges. Metallic bonds are formed between metal atoms and involve a 'sea of electrons' that are delocalized and free to move. Hydrogen bonds are a type of intermolecular force, not a true chemical bond, and occur between a hydrogen atom and a highly electronegative atom like oxygen or nitrogen.

3. To the nearest whole number, what is the mass of one mole of water?

• A. 16 g/mol
• B. 18 g/mol
• C. 20 g/mol
• D. 22 g/mol

Correct answer: B

Rationale: The molar mass of water (H₂O) is calculated by adding the atomic masses of two hydrogen atoms (each with a molar mass of approximately 1 g/mol) and one oxygen atom (with a molar mass of approximately 16 g/mol). Therefore, the molar mass of water is approximately 18 g/mol, making choice B the correct answer. Choice A (16 g/mol) is incorrect because it represents the molar mass of oxygen, not water. Choices C (20 g/mol) and D (22 g/mol) are incorrect as they do not correspond to the molar mass of water.

4. How many electron pairs are shared to form a triple covalent bond?

• A. 1
• B. 2
• C. 3
• D. 4

Correct answer: C

Rationale: The correct answer is C. In a triple covalent bond, three pairs of electrons are shared between two atoms. This sharing results in a total of six electrons being shared, making the bond strong. Choice A (1) is incorrect because a single covalent bond involves the sharing of one pair of electrons. Choice B (2) is incorrect as a double covalent bond consists of the sharing of two pairs of electrons. Choice D (4) is incorrect because there are only three pairs of electrons shared in a triple covalent bond, not four.

5. What is the name for the horizontal rows of the periodic table?

• A. groups
• B. periods
• C. families
• D. sets

Correct answer: B

Rationale: In the periodic table, 'periods' are the horizontal rows. Each period corresponds to the energy level occupied by the elements in that row. The other terms mentioned, such as groups, families, and sets, are not used to describe the horizontal rows but rather refer to different aspects of the periodic table organization. 'Groups' are the vertical columns, 'families' are groups of elements with similar properties, and 'sets' is a more generic term not specifically used in the context of the periodic table.

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